diff --git a/VERSION b/VERSION
new file mode 100644
index 00000000000000..139c590eb87892
--- /dev/null
+++ b/VERSION
@@ -0,0 +1,2 @@
+go1.23.4
+time 2024-11-27T20:27:20Z
diff --git a/codereview.cfg b/codereview.cfg
index 77a74f108eae36..3cf4bb2dd376de 100644
--- a/codereview.cfg
+++ b/codereview.cfg
@@ -1 +1,2 @@
-branch: master
+branch: release-branch.go1.23
+parent-branch: master
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 6c23e59adf19eb..be93c4a24bb566 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -2579,6 +2579,11 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 		if dt.BitSize > 0 {
 			fatalf("%s: unexpected: %d-bit int type - %s", lineno(pos), dt.BitSize, dtype)
 		}
+
+		if t.Align = t.Size; t.Align >= c.ptrSize {
+			t.Align = c.ptrSize
+		}
+
 		switch t.Size {
 		default:
 			fatalf("%s: unexpected: %d-byte int type - %s", lineno(pos), t.Size, dtype)
@@ -2595,9 +2600,8 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 				Len: c.intExpr(t.Size),
 				Elt: c.uint8,
 			}
-		}
-		if t.Align = t.Size; t.Align >= c.ptrSize {
-			t.Align = c.ptrSize
+			// t.Align is the alignment of the Go type.
+			t.Align = 1
 		}
 
 	case *dwarf.PtrType:
@@ -2826,6 +2830,11 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 		if dt.BitSize > 0 {
 			fatalf("%s: unexpected: %d-bit uint type - %s", lineno(pos), dt.BitSize, dtype)
 		}
+
+		if t.Align = t.Size; t.Align >= c.ptrSize {
+			t.Align = c.ptrSize
+		}
+
 		switch t.Size {
 		default:
 			fatalf("%s: unexpected: %d-byte uint type - %s", lineno(pos), t.Size, dtype)
@@ -2842,9 +2851,8 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 				Len: c.intExpr(t.Size),
 				Elt: c.uint8,
 			}
-		}
-		if t.Align = t.Size; t.Align >= c.ptrSize {
-			t.Align = c.ptrSize
+			// t.Align is the alignment of the Go type.
+			t.Align = 1
 		}
 
 	case *dwarf.VoidType:
@@ -3110,10 +3118,11 @@ func (c *typeConv) Struct(dt *dwarf.StructType, pos token.Pos) (expr *ast.Struct
 		}
 
 		// Round off up to talign, assumed to be a power of 2.
+		origOff := off
 		off = (off + talign - 1) &^ (talign - 1)
 
 		if f.ByteOffset > off {
-			fld, sizes = c.pad(fld, sizes, f.ByteOffset-off)
+			fld, sizes = c.pad(fld, sizes, f.ByteOffset-origOff)
 			off = f.ByteOffset
 		}
 		if f.ByteOffset < off {
diff --git a/src/cmd/cgo/internal/test/cgo_test.go b/src/cmd/cgo/internal/test/cgo_test.go
index 5e02888b3dddd9..5393552e07a4d1 100644
--- a/src/cmd/cgo/internal/test/cgo_test.go
+++ b/src/cmd/cgo/internal/test/cgo_test.go
@@ -70,6 +70,7 @@ func Test31891(t *testing.T)                 { test31891(t) }
 func Test42018(t *testing.T)                 { test42018(t) }
 func Test45451(t *testing.T)                 { test45451(t) }
 func Test49633(t *testing.T)                 { test49633(t) }
+func Test69086(t *testing.T)                 { test69086(t) }
 func TestAlign(t *testing.T)                 { testAlign(t) }
 func TestAtol(t *testing.T)                  { testAtol(t) }
 func TestBlocking(t *testing.T)              { testBlocking(t) }
diff --git a/src/cmd/cgo/internal/test/test.go b/src/cmd/cgo/internal/test/test.go
index 374689631d77ab..362be79a737bee 100644
--- a/src/cmd/cgo/internal/test/test.go
+++ b/src/cmd/cgo/internal/test/test.go
@@ -940,6 +940,19 @@ typedef struct {
 } issue67517struct;
 static void issue67517(issue67517struct* p) {}
 
+// Issue 69086.
+// GCC added the __int128 type in GCC 4.6, released in 2011.
+typedef struct {
+	int a;
+#ifdef __SIZEOF_INT128__
+	unsigned __int128 b;
+#else
+	uint64_t b;
+#endif
+	unsigned char c;
+} issue69086struct;
+static int issue690861(issue69086struct* p) { p->b = 1234; return p->c; }
+static int issue690862(unsigned long ul1, unsigned long ul2, unsigned int u, issue69086struct s) { return (int)(s.b); }
 */
 import "C"
 
@@ -2349,3 +2362,24 @@ func issue67517() {
 		b: nil,
 	})
 }
+
+// Issue 69086.
+func test69086(t *testing.T) {
+	var s C.issue69086struct
+
+	typ := reflect.TypeOf(s)
+	for i := 0; i < typ.NumField(); i++ {
+		f := typ.Field(i)
+		t.Logf("field %d: name %s size %d align %d offset %d", i, f.Name, f.Type.Size(), f.Type.Align(), f.Offset)
+	}
+
+	s.c = 1
+	got := C.issue690861(&s)
+	if got != 1 {
+		t.Errorf("field: got %d, want 1", got)
+	}
+	got = C.issue690862(1, 2, 3, s)
+	if got != 1234 {
+		t.Errorf("call: got %d, want 1234", got)
+	}
+}
diff --git a/src/cmd/cgo/internal/testcarchive/carchive_test.go b/src/cmd/cgo/internal/testcarchive/carchive_test.go
index a8eebead25dc9f..c263b82d5768f4 100644
--- a/src/cmd/cgo/internal/testcarchive/carchive_test.go
+++ b/src/cmd/cgo/internal/testcarchive/carchive_test.go
@@ -33,7 +33,7 @@ import (
 	"unicode"
 )
 
-var globalSkip = func(t *testing.T) {}
+var globalSkip = func(t testing.TB) {}
 
 // Program to run.
 var bin []string
@@ -59,12 +59,12 @@ func TestMain(m *testing.M) {
 
 func testMain(m *testing.M) int {
 	if testing.Short() && os.Getenv("GO_BUILDER_NAME") == "" {
-		globalSkip = func(t *testing.T) { t.Skip("short mode and $GO_BUILDER_NAME not set") }
+		globalSkip = func(t testing.TB) { t.Skip("short mode and $GO_BUILDER_NAME not set") }
 		return m.Run()
 	}
 	if runtime.GOOS == "linux" {
 		if _, err := os.Stat("/etc/alpine-release"); err == nil {
-			globalSkip = func(t *testing.T) { t.Skip("skipping failing test on alpine - go.dev/issue/19938") }
+			globalSkip = func(t testing.TB) { t.Skip("skipping failing test on alpine - go.dev/issue/19938") }
 			return m.Run()
 		}
 	}
@@ -1291,8 +1291,8 @@ func TestPreemption(t *testing.T) {
 	}
 }
 
-// Issue 59294. Test calling Go function from C after using some
-// stack space.
+// Issue 59294 and 68285. Test calling Go function from C after with
+// various stack space.
 func TestDeepStack(t *testing.T) {
 	globalSkip(t)
 	testenv.MustHaveGoBuild(t)
@@ -1350,6 +1350,53 @@ func TestDeepStack(t *testing.T) {
 	}
 }
 
+func BenchmarkCgoCallbackMainThread(b *testing.B) {
+	// Benchmark for calling into Go fron C main thread.
+	// See issue #68587.
+	//
+	// It uses a subprocess, which is a C binary that calls
+	// Go on the main thread b.N times. There is some overhead
+	// for launching the subprocess. It is probably fine when
+	// b.N is large.
+
+	globalSkip(b)
+	testenv.MustHaveGoBuild(b)
+	testenv.MustHaveCGO(b)
+	testenv.MustHaveBuildMode(b, "c-archive")
+
+	if !testWork {
+		defer func() {
+			os.Remove("testp10" + exeSuffix)
+			os.Remove("libgo10.a")
+			os.Remove("libgo10.h")
+		}()
+	}
+
+	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo10.a", "./libgo10")
+	out, err := cmd.CombinedOutput()
+	b.Logf("%v\n%s", cmd.Args, out)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	ccArgs := append(cc, "-o", "testp10"+exeSuffix, "main10.c", "libgo10.a")
+	out, err = exec.Command(ccArgs[0], ccArgs[1:]...).CombinedOutput()
+	b.Logf("%v\n%s", ccArgs, out)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	argv := cmdToRun("./testp10")
+	argv = append(argv, fmt.Sprint(b.N))
+	cmd = exec.Command(argv[0], argv[1:]...)
+
+	b.ResetTimer()
+	err = cmd.Run()
+	if err != nil {
+		b.Fatal(err)
+	}
+}
+
 func TestSharedObject(t *testing.T) {
 	// Test that we can put a Go c-archive into a C shared object.
 	globalSkip(t)
diff --git a/src/cmd/cgo/internal/testcarchive/testdata/libgo10/a.go b/src/cmd/cgo/internal/testcarchive/testdata/libgo10/a.go
new file mode 100644
index 00000000000000..803a0fa5f1cb35
--- /dev/null
+++ b/src/cmd/cgo/internal/testcarchive/testdata/libgo10/a.go
@@ -0,0 +1,12 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "C"
+
+//export GoF
+func GoF() {}
+
+func main() {}
diff --git a/src/cmd/cgo/internal/testcarchive/testdata/libgo9/a.go b/src/cmd/cgo/internal/testcarchive/testdata/libgo9/a.go
index acb08d90ecd5bf..3528bef654ddb3 100644
--- a/src/cmd/cgo/internal/testcarchive/testdata/libgo9/a.go
+++ b/src/cmd/cgo/internal/testcarchive/testdata/libgo9/a.go
@@ -6,9 +6,29 @@ package main
 
 import "runtime"
 
+// extern void callGoWithVariousStack(int);
 import "C"
 
 func main() {}
 
 //export GoF
-func GoF() { runtime.GC() }
+func GoF(p int32) {
+	runtime.GC()
+	if p != 0 {
+		panic("panic")
+	}
+}
+
+//export callGoWithVariousStackAndGoFrame
+func callGoWithVariousStackAndGoFrame(p int32) {
+	if p != 0 {
+		defer func() {
+			e := recover()
+			if e == nil {
+				panic("did not panic")
+			}
+			runtime.GC()
+		}()
+	}
+	C.callGoWithVariousStack(C.int(p));
+}
diff --git a/src/cmd/cgo/internal/testcarchive/testdata/main10.c b/src/cmd/cgo/internal/testcarchive/testdata/main10.c
new file mode 100644
index 00000000000000..53c3c83a99e35c
--- /dev/null
+++ b/src/cmd/cgo/internal/testcarchive/testdata/main10.c
@@ -0,0 +1,22 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "libgo10.h"
+
+int main(int argc, char **argv) {
+	int n, i;
+
+	if (argc != 2) {
+		perror("wrong arg");
+		return 2;
+	}
+	n = atoi(argv[1]);
+	for (i = 0; i < n; i++)
+		GoF();
+
+	return 0;
+}
diff --git a/src/cmd/cgo/internal/testcarchive/testdata/main9.c b/src/cmd/cgo/internal/testcarchive/testdata/main9.c
index 95ad4dea49fb1a..e641d8a8027a5f 100644
--- a/src/cmd/cgo/internal/testcarchive/testdata/main9.c
+++ b/src/cmd/cgo/internal/testcarchive/testdata/main9.c
@@ -6,19 +6,27 @@
 
 void use(int *x) { (*x)++; }
 
-void callGoFWithDeepStack() {
+void callGoFWithDeepStack(int p) {
 	int x[10000];
 
 	use(&x[0]);
 	use(&x[9999]);
 
-	GoF();
+	GoF(p);
 
 	use(&x[0]);
 	use(&x[9999]);
 }
 
+void callGoWithVariousStack(int p) {
+	GoF(0);                  // call GoF without using much stack
+	callGoFWithDeepStack(p); // call GoF with a deep stack
+	GoF(0);                  // again on a shallow stack
+}
+
 int main() {
-	GoF();                  // call GoF without using much stack
-	callGoFWithDeepStack(); // call GoF with a deep stack
+	callGoWithVariousStack(0);
+
+	callGoWithVariousStackAndGoFrame(0); // normal execution
+	callGoWithVariousStackAndGoFrame(1); // panic and recover
 }
diff --git a/src/cmd/compile/internal/escape/solve.go b/src/cmd/compile/internal/escape/solve.go
index 2675a16a241fe3..32f5a771a34a66 100644
--- a/src/cmd/compile/internal/escape/solve.go
+++ b/src/cmd/compile/internal/escape/solve.go
@@ -318,9 +318,10 @@ func containsClosure(f, c *ir.Func) bool {
 		return false
 	}
 
-	// Closures within function Foo are named like "Foo.funcN..."
-	// TODO(mdempsky): Better way to recognize this.
-	fn := f.Sym().Name
-	cn := c.Sym().Name
-	return len(cn) > len(fn) && cn[:len(fn)] == fn && cn[len(fn)] == '.'
+	for p := c.ClosureParent; p != nil; p = p.ClosureParent {
+		if p == f {
+			return true
+		}
+	}
+	return false
 }
diff --git a/src/cmd/compile/internal/importer/gcimporter_test.go b/src/cmd/compile/internal/importer/gcimporter_test.go
index 7fe4445dad7638..ffeddea0c9d588 100644
--- a/src/cmd/compile/internal/importer/gcimporter_test.go
+++ b/src/cmd/compile/internal/importer/gcimporter_test.go
@@ -582,6 +582,23 @@ func TestIssue25596(t *testing.T) {
 	compileAndImportPkg(t, "issue25596")
 }
 
+func TestIssue70394(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	pkg := compileAndImportPkg(t, "alias")
+	obj := lookupObj(t, pkg.Scope(), "A")
+
+	typ := obj.Type()
+	if _, ok := typ.(*types2.Alias); !ok {
+		t.Fatalf("type of %s is %s, wanted an alias", obj, typ)
+	}
+}
+
 func importPkg(t *testing.T, path, srcDir string) *types2.Package {
 	pkg, err := Import(make(map[string]*types2.Package), path, srcDir, nil)
 	if err != nil {
diff --git a/src/cmd/compile/internal/importer/testdata/alias.go b/src/cmd/compile/internal/importer/testdata/alias.go
new file mode 100644
index 00000000000000..51492fc943ea0c
--- /dev/null
+++ b/src/cmd/compile/internal/importer/testdata/alias.go
@@ -0,0 +1,7 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testdata
+
+type A = int32
diff --git a/src/cmd/compile/internal/importer/ureader.go b/src/cmd/compile/internal/importer/ureader.go
index d3c7d4516f7ee8..9d267e6db411c0 100644
--- a/src/cmd/compile/internal/importer/ureader.go
+++ b/src/cmd/compile/internal/importer/ureader.go
@@ -9,6 +9,7 @@ import (
 	"cmd/compile/internal/syntax"
 	"cmd/compile/internal/types2"
 	"cmd/internal/src"
+	"internal/buildcfg"
 	"internal/pkgbits"
 )
 
@@ -28,11 +29,9 @@ func ReadPackage(ctxt *types2.Context, imports map[string]*types2.Package, input
 	pr := pkgReader{
 		PkgDecoder: input,
 
-		ctxt:    ctxt,
-		imports: imports,
-		// Currently, the compiler panics when using Alias types.
-		// TODO(gri) set to true once this is fixed (issue #66873)
-		enableAlias: false,
+		ctxt:        ctxt,
+		imports:     imports,
+		enableAlias: true,
 
 		posBases: make([]*syntax.PosBase, input.NumElems(pkgbits.RelocPosBase)),
 		pkgs:     make([]*types2.Package, input.NumElems(pkgbits.RelocPkg)),
@@ -411,6 +410,14 @@ func (pr *pkgReader) objIdx(idx pkgbits.Index) (*types2.Package, string) {
 			panic("weird")
 
 		case pkgbits.ObjAlias:
+			if buildcfg.Experiment.AliasTypeParams && len(r.dict.bounds) > 0 {
+				// Temporary work-around for issue #68526: rather than panicking
+				// with an non-descriptive index-out-of-bounds panic when trying
+				// to access a missing type parameter, instead panic with a more
+				// descriptive error. Only needed for Go 1.23; Go 1.24 will have
+				// the correct implementation.
+				panic("importing generic type aliases is not supported in Go 1.23 (see issue #68526)")
+			}
 			pos := r.pos()
 			typ := r.typ()
 			return newAliasTypeName(pr.enableAlias, pos, objPkg, objName, typ)
diff --git a/src/cmd/compile/internal/ir/func.go b/src/cmd/compile/internal/ir/func.go
index d0c8ee359befff..4fa9055b4b2c0b 100644
--- a/src/cmd/compile/internal/ir/func.go
+++ b/src/cmd/compile/internal/ir/func.go
@@ -51,6 +51,8 @@ import (
 // the generated ODCLFUNC, but there is no
 // pointer from the Func back to the OMETHVALUE.
 type Func struct {
+	// if you add or remove a field, don't forget to update sizeof_test.go
+
 	miniNode
 	Body Nodes
 
@@ -76,6 +78,9 @@ type Func struct {
 	// Populated during walk.
 	Closures []*Func
 
+	// Parent of a closure
+	ClosureParent *Func
+
 	// Parents records the parent scope of each scope within a
 	// function. The root scope (0) has no parent, so the i'th
 	// scope's parent is stored at Parents[i-1].
@@ -512,6 +517,7 @@ func NewClosureFunc(fpos, cpos src.XPos, why Op, typ *types.Type, outerfn *Func,
 
 	fn.Nname.Defn = fn
 	pkg.Funcs = append(pkg.Funcs, fn)
+	fn.ClosureParent = outerfn
 
 	return fn
 }
diff --git a/src/cmd/compile/internal/ir/sizeof_test.go b/src/cmd/compile/internal/ir/sizeof_test.go
index 68d2865595b716..6331cceb4a59b4 100644
--- a/src/cmd/compile/internal/ir/sizeof_test.go
+++ b/src/cmd/compile/internal/ir/sizeof_test.go
@@ -20,7 +20,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr     // size on 32bit platforms
 		_64bit uintptr     // size on 64bit platforms
 	}{
-		{Func{}, 176, 296},
+		{Func{}, 180, 304},
 		{Name{}, 96, 168},
 	}
 
diff --git a/src/cmd/compile/internal/rangefunc/rangefunc_test.go b/src/cmd/compile/internal/rangefunc/rangefunc_test.go
index 97ab254395332a..e488c3cf377cae 100644
--- a/src/cmd/compile/internal/rangefunc/rangefunc_test.go
+++ b/src/cmd/compile/internal/rangefunc/rangefunc_test.go
@@ -2099,3 +2099,27 @@ func TestTwoLevelReturnCheck(t *testing.T) {
 		t.Errorf("Expected y=3, got y=%d\n", y)
 	}
 }
+
+func Bug70035(s1, s2, s3 []string) string {
+	var c1 string
+	for v1 := range slices.Values(s1) {
+		var c2 string
+		for v2 := range slices.Values(s2) {
+			var c3 string
+			for v3 := range slices.Values(s3) {
+				c3 = c3 + v3
+			}
+			c2 = c2 + v2 + c3
+		}
+		c1 = c1 + v1 + c2
+	}
+	return c1
+}
+
+func Test70035(t *testing.T) {
+	got := Bug70035([]string{"1", "2", "3"}, []string{"a", "b", "c"}, []string{"A", "B", "C"})
+	want := "1aABCbABCcABC2aABCbABCcABC3aABCbABCcABC"
+	if got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+}
diff --git a/src/cmd/compile/internal/types2/alias.go b/src/cmd/compile/internal/types2/alias.go
index 5148d5db034142..07f35b1854acaf 100644
--- a/src/cmd/compile/internal/types2/alias.go
+++ b/src/cmd/compile/internal/types2/alias.go
@@ -134,10 +134,10 @@ func (check *Checker) newAlias(obj *TypeName, rhs Type) *Alias {
 // newAliasInstance creates a new alias instance for the given origin and type
 // arguments, recording pos as the position of its synthetic object (for error
 // reporting).
-func (check *Checker) newAliasInstance(pos syntax.Pos, orig *Alias, targs []Type, ctxt *Context) *Alias {
+func (check *Checker) newAliasInstance(pos syntax.Pos, orig *Alias, targs []Type, expanding *Named, ctxt *Context) *Alias {
 	assert(len(targs) > 0)
 	obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
-	rhs := check.subst(pos, orig.fromRHS, makeSubstMap(orig.TypeParams().list(), targs), nil, ctxt)
+	rhs := check.subst(pos, orig.fromRHS, makeSubstMap(orig.TypeParams().list(), targs), expanding, ctxt)
 	res := check.newAlias(obj, rhs)
 	res.orig = orig
 	res.tparams = orig.tparams
diff --git a/src/cmd/compile/internal/types2/api_test.go b/src/cmd/compile/internal/types2/api_test.go
index 5126ac51116cd9..a6b105ace5cc33 100644
--- a/src/cmd/compile/internal/types2/api_test.go
+++ b/src/cmd/compile/internal/types2/api_test.go
@@ -2898,22 +2898,48 @@ func TestFileVersions(t *testing.T) {
 		fileVersion string
 		wantVersion string
 	}{
-		{"", "", ""},                   // no versions specified
-		{"go1.19", "", "go1.19"},       // module version specified
-		{"", "go1.20", ""},             // file upgrade ignored
-		{"go1.19", "go1.20", "go1.20"}, // file upgrade permitted
-		{"go1.20", "go1.19", "go1.20"}, // file downgrade not permitted
-		{"go1.21", "go1.19", "go1.19"}, // file downgrade permitted (module version is >= go1.21)
+		{"", "", ""},                    // no versions specified
+		{"go1.19", "", "go1.19"},        // module version specified
+		{"", "go1.20", "go1.21"},        // file version specified below minimum of 1.21
+		{"go1", "", "go1"},              // no file version specified
+		{"go1", "goo1.22", "go1"},       // invalid file version specified
+		{"go1", "go1.19", "go1.21"},     // file version specified below minimum of 1.21
+		{"go1", "go1.20", "go1.21"},     // file version specified below minimum of 1.21
+		{"go1", "go1.21", "go1.21"},     // file version specified at 1.21
+		{"go1", "go1.22", "go1.22"},     // file version specified above 1.21
+		{"go1.19", "", "go1.19"},        // no file version specified
+		{"go1.19", "goo1.22", "go1.19"}, // invalid file version specified
+		{"go1.19", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.19", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.19", "go1.22", "go1.22"},  // file version specified above 1.21
+		{"go1.20", "", "go1.20"},        // no file version specified
+		{"go1.20", "goo1.22", "go1.20"}, // invalid file version specified
+		{"go1.20", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.20", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.20", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.20", "go1.22", "go1.22"},  // file version specified above 1.21
+		{"go1.21", "", "go1.21"},        // no file version specified
+		{"go1.21", "goo1.22", "go1.21"}, // invalid file version specified
+		{"go1.21", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.21", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.21", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.21", "go1.22", "go1.22"},  // file version specified above 1.21
+		{"go1.22", "", "go1.22"},        // no file version specified
+		{"go1.22", "goo1.22", "go1.22"}, // invalid file version specified
+		{"go1.22", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.22", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.22", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.22", "go1.22", "go1.22"},  // file version specified above 1.21
 
 		// versions containing release numbers
 		// (file versions containing release numbers are considered invalid)
 		{"go1.19.0", "", "go1.19.0"},         // no file version specified
-		{"go1.20", "go1.20.1", "go1.20"},     // file upgrade ignored
-		{"go1.20.1", "go1.20", "go1.20.1"},   // file upgrade ignored
-		{"go1.20.1", "go1.21", "go1.21"},     // file upgrade permitted
-		{"go1.20.1", "go1.19", "go1.20.1"},   // file downgrade not permitted
-		{"go1.21.1", "go1.19.1", "go1.21.1"}, // file downgrade not permitted (invalid file version)
-		{"go1.21.1", "go1.19", "go1.19"},     // file downgrade permitted (module version is >= go1.21)
+		{"go1.20.1", "go1.19.1", "go1.20.1"}, // invalid file version
+		{"go1.20.1", "go1.21.1", "go1.20.1"}, // invalid file version
+		{"go1.21.1", "go1.19.1", "go1.21.1"}, // invalid file version
+		{"go1.21.1", "go1.21.1", "go1.21.1"}, // invalid file version
+		{"go1.22.1", "go1.19.1", "go1.22.1"}, // invalid file version
+		{"go1.22.1", "go1.21.1", "go1.22.1"}, // invalid file version
 	} {
 		var src string
 		if test.fileVersion != "" {
diff --git a/src/cmd/compile/internal/types2/check.go b/src/cmd/compile/internal/types2/check.go
index 91ad474e9df315..ada421ba939ed4 100644
--- a/src/cmd/compile/internal/types2/check.go
+++ b/src/cmd/compile/internal/types2/check.go
@@ -327,7 +327,6 @@ func (check *Checker) initFiles(files []*syntax.File) {
 		check.errorf(files[0], TooNew, "package requires newer Go version %v (application built with %v)",
 			check.version, go_current)
 	}
-	downgradeOk := check.version.cmp(go1_21) >= 0
 
 	// determine Go version for each file
 	for _, file := range check.files {
@@ -336,33 +335,18 @@ func (check *Checker) initFiles(files []*syntax.File) {
 		// unlike file versions which are Go language versions only, if valid.)
 		v := check.conf.GoVersion
 
-		fileVersion := asGoVersion(file.GoVersion)
-		if fileVersion.isValid() {
-			// use the file version, if applicable
-			// (file versions are either the empty string or of the form go1.dd)
-			if pkgVersionOk {
-				cmp := fileVersion.cmp(check.version)
-				// Go 1.21 introduced the feature of setting the go.mod
-				// go line to an early version of Go and allowing //go:build lines
-				// to “upgrade” (cmp > 0) the Go version in a given file.
-				// We can do that backwards compatibly.
-				//
-				// Go 1.21 also introduced the feature of allowing //go:build lines
-				// to “downgrade” (cmp < 0) the Go version in a given file.
-				// That can't be done compatibly in general, since before the
-				// build lines were ignored and code got the module's Go version.
-				// To work around this, downgrades are only allowed when the
-				// module's Go version is Go 1.21 or later.
-				//
-				// If there is no valid check.version, then we don't really know what
-				// Go version to apply.
-				// Legacy tools may do this, and they historically have accepted everything.
-				// Preserve that behavior by ignoring //go:build constraints entirely in that
-				// case (!pkgVersionOk).
-				if cmp > 0 || cmp < 0 && downgradeOk {
-					v = file.GoVersion
-				}
-			}
+		// If the file specifies a version, use max(fileVersion, go1.21).
+		if fileVersion := asGoVersion(file.GoVersion); fileVersion.isValid() {
+			// Go 1.21 introduced the feature of allowing //go:build lines
+			// to sometimes set the Go version in a given file. Versions Go 1.21 and later
+			// can be set backwards compatibly as that was the first version
+			// files with go1.21 or later build tags could be built with.
+			//
+			// Set the version to max(fileVersion, go1.21): That will allow a
+			// downgrade to a version before go1.22, where the for loop semantics
+			// change was made, while being backwards compatible with versions of
+			// go before the new //go:build semantics were introduced.
+			v = string(versionMax(fileVersion, go1_21))
 
 			// Report a specific error for each tagged file that's too new.
 			// (Normally the build system will have filtered files by version,
@@ -377,6 +361,13 @@ func (check *Checker) initFiles(files []*syntax.File) {
 	}
 }
 
+func versionMax(a, b goVersion) goVersion {
+	if a.cmp(b) > 0 {
+		return a
+	}
+	return b
+}
+
 // A bailout panic is used for early termination.
 type bailout struct{}
 
diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index 72227ab12256dd..308d1f550ad4fa 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -11,6 +11,7 @@ import (
 	"cmd/compile/internal/syntax"
 	"errors"
 	"fmt"
+	"internal/buildcfg"
 	. "internal/types/errors"
 )
 
@@ -126,8 +127,9 @@ func (check *Checker) instance(pos syntax.Pos, orig genericType, targs []Type, e
 		res = check.newNamedInstance(pos, orig, targs, expanding) // substituted lazily
 
 	case *Alias:
-		// TODO(gri) is this correct?
-		assert(expanding == nil) // Alias instances cannot be reached from Named types
+		if !buildcfg.Experiment.AliasTypeParams {
+			assert(expanding == nil) // Alias instances cannot be reached from Named types
+		}
 
 		tparams := orig.TypeParams()
 		// TODO(gri) investigate if this is needed (type argument and parameter count seem to be correct here)
@@ -138,7 +140,7 @@ func (check *Checker) instance(pos syntax.Pos, orig genericType, targs []Type, e
 			return orig // nothing to do (minor optimization)
 		}
 
-		return check.newAliasInstance(pos, orig, targs, ctxt)
+		return check.newAliasInstance(pos, orig, targs, expanding, ctxt)
 
 	case *Signature:
 		assert(expanding == nil) // function instances cannot be reached from Named types
diff --git a/src/cmd/compile/internal/types2/issues_test.go b/src/cmd/compile/internal/types2/issues_test.go
index 20e3f52facd9de..b339def7354e28 100644
--- a/src/cmd/compile/internal/types2/issues_test.go
+++ b/src/cmd/compile/internal/types2/issues_test.go
@@ -1121,3 +1121,23 @@ func f(x int) {
 		t.Errorf("got: %s want: %s", got, want)
 	}
 }
+
+func TestIssue68877(t *testing.T) {
+	const src = `
+package p
+
+type (
+	S struct{}
+	A = S
+	T A
+)`
+
+	conf := Config{EnableAlias: true}
+	pkg := mustTypecheck(src, &conf, nil)
+	T := pkg.Scope().Lookup("T").(*TypeName)
+	got := T.String() // this must not panic (was issue)
+	const want = "type p.T struct{}"
+	if got != want {
+		t.Errorf("got %s, want %s", got, want)
+	}
+}
diff --git a/src/cmd/compile/internal/types2/named.go b/src/cmd/compile/internal/types2/named.go
index 1859b27aa4edfb..02b5ecf1669ea5 100644
--- a/src/cmd/compile/internal/types2/named.go
+++ b/src/cmd/compile/internal/types2/named.go
@@ -282,7 +282,7 @@ func (t *Named) cleanup() {
 		if t.TypeArgs().Len() == 0 {
 			panic("nil underlying")
 		}
-	case *Named:
+	case *Named, *Alias:
 		t.under() // t.under may add entries to check.cleaners
 	}
 	t.check = nil
diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index 650ae846a61e85..7c4cd732501e43 100644
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -115,7 +115,7 @@ func (subst *subster) typ(typ Type) Type {
 		// that has a type argument for it.
 		targs, updated := subst.typeList(t.TypeArgs().list())
 		if updated {
-			return subst.check.newAliasInstance(subst.pos, t.orig, targs, subst.ctxt)
+			return subst.check.newAliasInstance(subst.pos, t.orig, targs, subst.expanding, subst.ctxt)
 		}
 
 	case *Array:
diff --git a/src/cmd/compile/internal/types2/typeset.go b/src/cmd/compile/internal/types2/typeset.go
index 0457502e393942..a2d9e42c615ca4 100644
--- a/src/cmd/compile/internal/types2/typeset.go
+++ b/src/cmd/compile/internal/types2/typeset.go
@@ -131,8 +131,8 @@ func (s *_TypeSet) underIs(f func(Type) bool) bool {
 	}
 	for _, t := range s.terms {
 		assert(t.typ != nil)
-		// x == under(x) for ~x terms
-		u := t.typ
+		// Unalias(x) == under(x) for ~x terms
+		u := Unalias(t.typ)
 		if !t.tilde {
 			u = under(u)
 		}
diff --git a/src/cmd/go.mod b/src/cmd/go.mod
index 49f02012d3103a..484fef03d10a16 100644
--- a/src/cmd/go.mod
+++ b/src/cmd/go.mod
@@ -9,7 +9,7 @@ require (
 	golang.org/x/mod v0.19.0
 	golang.org/x/sync v0.7.0
 	golang.org/x/sys v0.22.0
-	golang.org/x/telemetry v0.0.0-20240717194752-0b706e19b701
+	golang.org/x/telemetry v0.0.0-20240828213427-40b6b7fe7147
 	golang.org/x/term v0.20.0
 	golang.org/x/tools v0.22.1-0.20240618181713-f2d2ebe43e72
 )
diff --git a/src/cmd/go.sum b/src/cmd/go.sum
index ee671f95122344..919dbd2dc74c74 100644
--- a/src/cmd/go.sum
+++ b/src/cmd/go.sum
@@ -16,8 +16,8 @@ golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
 golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/telemetry v0.0.0-20240717194752-0b706e19b701 h1:+bltxAtk8YFEQ61B/lcYQM8e+7XjLwSDbpspVaVYkz8=
-golang.org/x/telemetry v0.0.0-20240717194752-0b706e19b701/go.mod h1:amNmu/SBSm2GAF3X+9U2C0epLocdh+r5Z+7oMYO5cLM=
+golang.org/x/telemetry v0.0.0-20240828213427-40b6b7fe7147 h1:Lj8KbuZmoFUbI6pQ28G3Diz/5bRYD2UY5vfAmhrLZWo=
+golang.org/x/telemetry v0.0.0-20240828213427-40b6b7fe7147/go.mod h1:amNmu/SBSm2GAF3X+9U2C0epLocdh+r5Z+7oMYO5cLM=
 golang.org/x/term v0.20.0 h1:VnkxpohqXaOBYJtBmEppKUG6mXpi+4O6purfc2+sMhw=
 golang.org/x/term v0.20.0/go.mod h1:8UkIAJTvZgivsXaD6/pH6U9ecQzZ45awqEOzuCvwpFY=
 golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 0d8455d92e336b..bc484dedf6ed54 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -805,13 +805,19 @@ func elfwritefreebsdsig(out *OutBuf) int {
 	return int(sh.Size)
 }
 
-func addbuildinfo(val string) {
+func addbuildinfo(ctxt *Link) {
+	val := *flagHostBuildid
 	if val == "gobuildid" {
 		buildID := *flagBuildid
 		if buildID == "" {
 			Exitf("-B gobuildid requires a Go build ID supplied via -buildid")
 		}
 
+		if ctxt.IsDarwin() {
+			buildinfo = uuidFromGoBuildId(buildID)
+			return
+		}
+
 		hashedBuildID := notsha256.Sum256([]byte(buildID))
 		buildinfo = hashedBuildID[:20]
 
@@ -821,11 +827,13 @@ func addbuildinfo(val string) {
 	if !strings.HasPrefix(val, "0x") {
 		Exitf("-B argument must start with 0x: %s", val)
 	}
-
 	ov := val
 	val = val[2:]
 
-	const maxLen = 32
+	maxLen := 32
+	if ctxt.IsDarwin() {
+		maxLen = 16
+	}
 	if hex.DecodedLen(len(val)) > maxLen {
 		Exitf("-B option too long (max %d digits): %s", maxLen, ov)
 	}
diff --git a/src/cmd/link/internal/ld/macho.go b/src/cmd/link/internal/ld/macho.go
index 34624c25a9f333..c5a85f0e75e7cf 100644
--- a/src/cmd/link/internal/ld/macho.go
+++ b/src/cmd/link/internal/ld/macho.go
@@ -297,6 +297,8 @@ func getMachoHdr() *MachoHdr {
 	return &machohdr
 }
 
+// Create a new Mach-O load command. ndata is the number of 32-bit words for
+// the data (not including the load command header).
 func newMachoLoad(arch *sys.Arch, type_ uint32, ndata uint32) *MachoLoad {
 	if arch.PtrSize == 8 && (ndata&1 != 0) {
 		ndata++
@@ -849,6 +851,20 @@ func asmbMacho(ctxt *Link) {
 			}
 		}
 
+		if ctxt.IsInternal() && len(buildinfo) > 0 {
+			ml := newMachoLoad(ctxt.Arch, LC_UUID, 4)
+			// Mach-O UUID is 16 bytes
+			if len(buildinfo) < 16 {
+				buildinfo = append(buildinfo, make([]byte, 16)...)
+			}
+			// By default, buildinfo is already in UUIDv3 format
+			// (see uuidFromGoBuildId).
+			ml.data[0] = ctxt.Arch.ByteOrder.Uint32(buildinfo)
+			ml.data[1] = ctxt.Arch.ByteOrder.Uint32(buildinfo[4:])
+			ml.data[2] = ctxt.Arch.ByteOrder.Uint32(buildinfo[8:])
+			ml.data[3] = ctxt.Arch.ByteOrder.Uint32(buildinfo[12:])
+		}
+
 		if ctxt.IsInternal() && ctxt.NeedCodeSign() {
 			ml := newMachoLoad(ctxt.Arch, LC_CODE_SIGNATURE, 2)
 			ml.data[0] = uint32(codesigOff)
diff --git a/src/cmd/link/internal/ld/macho_update_uuid.go b/src/cmd/link/internal/ld/macho_update_uuid.go
index de27e655d59bf4..40e0c11ed19d6e 100644
--- a/src/cmd/link/internal/ld/macho_update_uuid.go
+++ b/src/cmd/link/internal/ld/macho_update_uuid.go
@@ -42,7 +42,7 @@ func uuidFromGoBuildId(buildID string) []byte {
 	// to use this UUID flavor than any of the others. This is similar
 	// to how other linkers handle this (for example this code in lld:
 	// https://github.com/llvm/llvm-project/blob/2a3a79ce4c2149d7787d56f9841b66cacc9061d0/lld/MachO/Writer.cpp#L524).
-	rv[6] &= 0xcf
+	rv[6] &= 0x0f
 	rv[6] |= 0x30
 	rv[8] &= 0x3f
 	rv[8] |= 0xc0
diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go
index 56e865d8a53287..12bc896c66c3d7 100644
--- a/src/cmd/link/internal/ld/main.go
+++ b/src/cmd/link/internal/ld/main.go
@@ -95,6 +95,7 @@ var (
 	flagN             = flag.Bool("n", false, "no-op (deprecated)")
 	FlagS             = flag.Bool("s", false, "disable symbol table")
 	flag8             bool // use 64-bit addresses in symbol table
+	flagHostBuildid   = flag.String("B", "", "set ELF NT_GNU_BUILD_ID `note` or Mach-O UUID; use \"gobuildid\" to generate it from the Go build ID")
 	flagInterpreter   = flag.String("I", "", "use `linker` as ELF dynamic linker")
 	flagCheckLinkname = flag.Bool("checklinkname", true, "check linkname symbol references")
 	FlagDebugTramp    = flag.Int("debugtramp", 0, "debug trampolines")
@@ -196,7 +197,6 @@ func Main(arch *sys.Arch, theArch Arch) {
 	flag.Var(&ctxt.LinkMode, "linkmode", "set link `mode`")
 	flag.Var(&ctxt.BuildMode, "buildmode", "set build `mode`")
 	flag.BoolVar(&ctxt.compressDWARF, "compressdwarf", true, "compress DWARF if possible")
-	objabi.Flagfn1("B", "add an ELF NT_GNU_BUILD_ID `note` when using ELF; use \"gobuildid\" to generate it from the Go build ID", addbuildinfo)
 	objabi.Flagfn1("L", "add specified `directory` to library path", func(a string) { Lflag(ctxt, a) })
 	objabi.AddVersionFlag() // -V
 	objabi.Flagfn1("X", "add string value `definition` of the form importpath.name=value", func(s string) { addstrdata1(ctxt, s) })
@@ -294,6 +294,10 @@ func Main(arch *sys.Arch, theArch Arch) {
 		*flagBuildid = "go-openbsd"
 	}
 
+	if *flagHostBuildid != "" {
+		addbuildinfo(ctxt)
+	}
+
 	// enable benchmarking
 	var bench *benchmark.Metrics
 	if len(*benchmarkFlag) != 0 {
diff --git a/src/cmd/trace/gstate.go b/src/cmd/trace/gstate.go
index 638d492670a6e7..4b380db9f53cd7 100644
--- a/src/cmd/trace/gstate.go
+++ b/src/cmd/trace/gstate.go
@@ -257,6 +257,10 @@ func (gs *gState[R]) stop(ts trace.Time, stack trace.Stack, ctx *traceContext) {
 	if gs.lastStopStack != trace.NoStack {
 		stk = ctx.Stack(viewerFrames(gs.lastStopStack))
 	}
+	var endStk int
+	if stack != trace.NoStack {
+		endStk = ctx.Stack(viewerFrames(stack))
+	}
 	// Check invariants.
 	if gs.startRunningTime == 0 {
 		panic("silently broken trace or generator invariant (startRunningTime != 0) not held")
@@ -270,6 +274,7 @@ func (gs *gState[R]) stop(ts trace.Time, stack trace.Stack, ctx *traceContext) {
 		Dur:      ts.Sub(gs.startRunningTime),
 		Resource: uint64(gs.executing),
 		Stack:    stk,
+		EndStack: endStk,
 	})
 
 	// Flush completed ranges.
diff --git a/src/cmd/vendor/golang.org/x/telemetry/internal/configstore/download.go b/src/cmd/vendor/golang.org/x/telemetry/internal/configstore/download.go
index a38f371d0f51b6..e60ab7e9fdd73e 100644
--- a/src/cmd/vendor/golang.org/x/telemetry/internal/configstore/download.go
+++ b/src/cmd/vendor/golang.org/x/telemetry/internal/configstore/download.go
@@ -16,6 +16,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"sync/atomic"
 
 	"golang.org/x/telemetry/internal/telemetry"
 )
@@ -29,12 +30,22 @@ const (
 // creation flag.
 var needNoConsole = func(cmd *exec.Cmd) {}
 
+var downloads int64
+
+// Downloads reports, for testing purposes, the number of times [Download] has
+// been called.
+func Downloads() int64 {
+	return atomic.LoadInt64(&downloads)
+}
+
 // Download fetches the requested telemetry UploadConfig using "go mod
 // download". If envOverlay is provided, it is appended to the environment used
 // for invoking the go command.
 //
 // The second result is the canonical version of the requested configuration.
 func Download(version string, envOverlay []string) (*telemetry.UploadConfig, string, error) {
+	atomic.AddInt64(&downloads, 1)
+
 	if version == "" {
 		version = "latest"
 	}
diff --git a/src/cmd/vendor/golang.org/x/telemetry/internal/crashmonitor/monitor.go b/src/cmd/vendor/golang.org/x/telemetry/internal/crashmonitor/monitor.go
index f475f7eec2dfce..612f7563a74c9f 100644
--- a/src/cmd/vendor/golang.org/x/telemetry/internal/crashmonitor/monitor.go
+++ b/src/cmd/vendor/golang.org/x/telemetry/internal/crashmonitor/monitor.go
@@ -21,12 +21,12 @@ import (
 	"golang.org/x/telemetry/internal/counter"
 )
 
-// Supported reports whether the runtime supports [runtime.SetCrashOutput].
+// Supported reports whether the runtime supports [runtime/debug.SetCrashOutput].
 //
 // TODO(adonovan): eliminate once go1.23+ is assured.
 func Supported() bool { return setCrashOutput != nil }
 
-var setCrashOutput func(*os.File) error // = runtime.SetCrashOutput on go1.23+
+var setCrashOutput func(*os.File) error // = runtime/debug.SetCrashOutput on go1.23+
 
 // Parent sets up the parent side of the crashmonitor. It requires
 // exclusive use of a writable pipe connected to the child process's stdin.
diff --git a/src/cmd/vendor/golang.org/x/telemetry/internal/upload/run.go b/src/cmd/vendor/golang.org/x/telemetry/internal/upload/run.go
index eba13b1a573560..e9c8dc207126a1 100644
--- a/src/cmd/vendor/golang.org/x/telemetry/internal/upload/run.go
+++ b/src/cmd/vendor/golang.org/x/telemetry/internal/upload/run.go
@@ -112,9 +112,24 @@ func newUploader(rcfg RunConfig) (*uploader, error) {
 	logger := log.New(logWriter, "", log.Ltime|log.Lmicroseconds|log.Lshortfile)
 
 	// Fetch the upload config, if it is not provided.
-	config, configVersion, err := configstore.Download("latest", rcfg.Env)
-	if err != nil {
-		return nil, err
+	var (
+		config        *telemetry.UploadConfig
+		configVersion string
+	)
+
+	if mode, _ := dir.Mode(); mode == "on" {
+		// golang/go#68946: only download the upload config if it will be used.
+		//
+		// TODO(rfindley): This is a narrow change aimed at minimally fixing the
+		// associated bug. In the future, we should read the mode only once during
+		// the upload process.
+		config, configVersion, err = configstore.Download("latest", rcfg.Env)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		config = &telemetry.UploadConfig{}
+		configVersion = "v0.0.0-0"
 	}
 
 	// Set the start time, if it is not provided.
diff --git a/src/cmd/vendor/golang.org/x/telemetry/start.go b/src/cmd/vendor/golang.org/x/telemetry/start.go
index 4b37a5c3945cd5..69ebcc71359405 100644
--- a/src/cmd/vendor/golang.org/x/telemetry/start.go
+++ b/src/cmd/vendor/golang.org/x/telemetry/start.go
@@ -206,7 +206,8 @@ func startChild(reportCrashes, upload bool, result *StartResult) {
 	fd, err := os.Stat(telemetry.Default.DebugDir())
 	if err != nil {
 		if !os.IsNotExist(err) {
-			log.Fatalf("failed to stat debug directory: %v", err)
+			log.Printf("failed to stat debug directory: %v", err)
+			return
 		}
 	} else if fd.IsDir() {
 		// local/debug exists and is a directory. Set stderr to a log file path
@@ -214,23 +215,31 @@ func startChild(reportCrashes, upload bool, result *StartResult) {
 		childLogPath := filepath.Join(telemetry.Default.DebugDir(), "sidecar.log")
 		childLog, err := os.OpenFile(childLogPath, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0600)
 		if err != nil {
-			log.Fatalf("opening sidecar log file for child: %v", err)
+			log.Printf("opening sidecar log file for child: %v", err)
+			return
 		}
 		defer childLog.Close()
 		cmd.Stderr = childLog
 	}
 
+	var crashOutputFile *os.File
 	if reportCrashes {
 		pipe, err := cmd.StdinPipe()
 		if err != nil {
-			log.Fatalf("StdinPipe: %v", err)
+			log.Printf("StdinPipe: %v", err)
+			return
 		}
 
-		crashmonitor.Parent(pipe.(*os.File)) // (this conversion is safe)
+		crashOutputFile = pipe.(*os.File) // (this conversion is safe)
 	}
 
 	if err := cmd.Start(); err != nil {
-		log.Fatalf("can't start telemetry child process: %v", err)
+		// The child couldn't be started. Log the failure.
+		log.Printf("can't start telemetry child process: %v", err)
+		return
+	}
+	if reportCrashes {
+		crashmonitor.Parent(crashOutputFile)
 	}
 	result.wg.Add(1)
 	go func() {
diff --git a/src/cmd/vendor/modules.txt b/src/cmd/vendor/modules.txt
index bf9c1341b94f73..22d40b9e4c1385 100644
--- a/src/cmd/vendor/modules.txt
+++ b/src/cmd/vendor/modules.txt
@@ -45,7 +45,7 @@ golang.org/x/sync/semaphore
 golang.org/x/sys/plan9
 golang.org/x/sys/unix
 golang.org/x/sys/windows
-# golang.org/x/telemetry v0.0.0-20240717194752-0b706e19b701
+# golang.org/x/telemetry v0.0.0-20240828213427-40b6b7fe7147
 ## explicit; go 1.20
 golang.org/x/telemetry
 golang.org/x/telemetry/counter
diff --git a/src/context/context.go b/src/context/context.go
index 763d4f777ffb86..73739bc90ea79f 100644
--- a/src/context/context.go
+++ b/src/context/context.go
@@ -59,6 +59,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"time"
+	_ "unsafe"  // for go:linkname
 )
 
 // A Context carries a deadline, a cancellation signal, and other values across
@@ -361,6 +362,7 @@ type stopCtx struct {
 var goroutines atomic.Int32
 
 // &cancelCtxKey is the key that a cancelCtx returns itself for.
+//go:linkname cancelCtxKey
 var cancelCtxKey int
 
 // parentCancelCtx returns the underlying *cancelCtx for parent.
@@ -477,17 +479,7 @@ func (c *cancelCtx) propagateCancel(parent Context, child canceler) {
 
 	if p, ok := parentCancelCtx(parent); ok {
 		// parent is a *cancelCtx, or derives from one.
-		p.mu.Lock()
-		if p.err != nil {
-			// parent has already been canceled
-			child.cancel(false, p.err, p.cause)
-		} else {
-			if p.children == nil {
-				p.children = make(map[canceler]struct{})
-			}
-			p.children[child] = struct{}{}
-		}
-		p.mu.Unlock()
+		p.addChild(child)
 		return
 	}
 
@@ -515,6 +507,22 @@ func (c *cancelCtx) propagateCancel(parent Context, child canceler) {
 	}()
 }
 
+// addChild adds child to the list of children.
+// NB: CockroachDB runtime patch.
+func (c *cancelCtx) addChild(child canceler) {
+	c.mu.Lock()
+	if c.err != nil {
+		// parent has already been canceled
+		child.cancel(false, c.err, c.cause)
+	} else {
+		if c.children == nil {
+			c.children = make(map[canceler]struct{})
+		}
+		c.children[child] = struct{}{}
+	}
+	c.mu.Unlock()
+}
+
 type stringer interface {
 	String() string
 }
@@ -790,3 +798,33 @@ func value(c Context, key any) any {
 		}
 	}
 }
+
+// CockroachDB runtime patch.
+// cancelerAdapter invokes f when cancel context completes.
+type cancelerAdapter struct {
+	*cancelCtx
+	f func()
+}
+
+func (c *cancelerAdapter) cancel(removeFromParent bool, err, cause error) {
+	if removeFromParent {
+		removeChild(c.cancelCtx, c)
+	}
+	c.f()
+}
+
+// PropagateCancel arranges for f to be invoked when parent is done.
+// Parent must be one of the cancelable contexts.
+// Returns true if cancellation will be propagated, false if the parent
+// is not cancelable.
+// This is similar to AfterFunc(), but does not spin up goroutine, and instead
+// invokes f on whatever goroutine completed parent context.
+func PropagateCancel(parent Context, f func()) bool {
+	p, ok := parent.Value(&cancelCtxKey).(*cancelCtx)
+	if !ok {
+		return false
+	}
+	a := cancelerAdapter{cancelCtx: p, f: f}
+	p.addChild(&a)
+	return true
+}
diff --git a/src/crypto/md5/md5.go b/src/crypto/md5/md5.go
index 843678702bf93f..979b4533221858 100644
--- a/src/crypto/md5/md5.go
+++ b/src/crypto/md5/md5.go
@@ -27,6 +27,10 @@ const Size = 16
 // The blocksize of MD5 in bytes.
 const BlockSize = 64
 
+// The maximum number of bytes that can be passed to block.
+const maxAsmIters = 1024
+const maxAsmSize = BlockSize * maxAsmIters // 64KiB
+
 const (
 	init0 = 0x67452301
 	init1 = 0xEFCDAB89
@@ -130,6 +134,11 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 	if len(p) >= BlockSize {
 		n := len(p) &^ (BlockSize - 1)
 		if haveAsm {
+			for n > maxAsmSize {
+				block(d, p[:maxAsmSize])
+				p = p[maxAsmSize:]
+				n -= maxAsmSize
+			}
 			block(d, p[:n])
 		} else {
 			blockGeneric(d, p[:n])
diff --git a/src/crypto/md5/md5_test.go b/src/crypto/md5/md5_test.go
index a5b661126dd716..5285a13724d23d 100644
--- a/src/crypto/md5/md5_test.go
+++ b/src/crypto/md5/md5_test.go
@@ -121,10 +121,11 @@ func TestGoldenMarshal(t *testing.T) {
 
 func TestLarge(t *testing.T) {
 	const N = 10000
+	const offsets = 4
 	ok := "2bb571599a4180e1d542f76904adc3df" // md5sum of "0123456789" * 1000
-	block := make([]byte, 10004)
+	block := make([]byte, N+offsets)
 	c := New()
-	for offset := 0; offset < 4; offset++ {
+	for offset := 0; offset < offsets; offset++ {
 		for i := 0; i < N; i++ {
 			block[offset+i] = '0' + byte(i%10)
 		}
@@ -143,6 +144,32 @@ func TestLarge(t *testing.T) {
 	}
 }
 
+func TestExtraLarge(t *testing.T) {
+	const N = 100000
+	const offsets = 4
+	ok := "13572e9e296cff52b79c52148313c3a5" // md5sum of "0123456789" * 10000
+	block := make([]byte, N+offsets)
+	c := New()
+	for offset := 0; offset < offsets; offset++ {
+		for i := 0; i < N; i++ {
+			block[offset+i] = '0' + byte(i%10)
+		}
+		for blockSize := 10; blockSize <= N; blockSize *= 10 {
+			blocks := N / blockSize
+			b := block[offset : offset+blockSize]
+			c.Reset()
+			for i := 0; i < blocks; i++ {
+				c.Write(b)
+			}
+			s := fmt.Sprintf("%x", c.Sum(nil))
+			if s != ok {
+				t.Fatalf("md5 TestExtraLarge offset=%d, blockSize=%d = %s want %s", offset, blockSize, s, ok)
+			}
+		}
+	}
+}
+
+
 // Tests that blockGeneric (pure Go) and block (in assembly for amd64, 386, arm) match.
 func TestBlockGeneric(t *testing.T) {
 	gen, asm := New().(*digest), New().(*digest)
diff --git a/src/crypto/sha256/sha256.go b/src/crypto/sha256/sha256.go
index 68244fd63b0c1e..a2f669fa9ccb96 100644
--- a/src/crypto/sha256/sha256.go
+++ b/src/crypto/sha256/sha256.go
@@ -28,6 +28,10 @@ const Size224 = 28
 // The blocksize of SHA256 and SHA224 in bytes.
 const BlockSize = 64
 
+// The maximum number of bytes that can be passed to block.
+const maxAsmIters = 1024
+const maxAsmSize = BlockSize * maxAsmIters // 64KiB
+
 const (
 	chunk     = 64
 	init0     = 0x6A09E667
@@ -186,6 +190,11 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 	}
 	if len(p) >= chunk {
 		n := len(p) &^ (chunk - 1)
+		for n > maxAsmSize {
+			block(d, p[:maxAsmSize])
+			p = p[maxAsmSize:]
+			n -= maxAsmSize
+		}
 		block(d, p[:n])
 		p = p[n:]
 	}
diff --git a/src/crypto/sha256/sha256_test.go b/src/crypto/sha256/sha256_test.go
index d91f01e9ba3a5f..f5dd4025d25ecf 100644
--- a/src/crypto/sha256/sha256_test.go
+++ b/src/crypto/sha256/sha256_test.go
@@ -184,6 +184,58 @@ func TestGoldenMarshal(t *testing.T) {
 	}
 }
 
+
+
+func TestLarge(t *testing.T) {
+	const N = 10000
+	const offsets = 4
+	ok := "4c207598af7a20db0e3334dd044399a40e467cb81b37f7ba05a4f76dcbd8fd59" // sha256sum of "0123456789" * 1000
+	block := make([]byte, N+offsets)
+	c := New()
+	for offset := 0; offset < offsets; offset++ {
+		for i := 0; i < N; i++ {
+			block[offset+i] = '0' + byte(i%10)
+		}
+		for blockSize := 10; blockSize <= N; blockSize *= 10 {
+			blocks := N / blockSize
+			b := block[offset : offset+blockSize]
+			c.Reset()
+			for i := 0; i < blocks; i++ {
+				c.Write(b)
+			}
+			s := fmt.Sprintf("%x", c.Sum(nil))
+			if s != ok {
+				t.Fatalf("sha256 TestLarge offset=%d, blockSize=%d = %s want %s", offset, blockSize, s, ok)
+			}
+		}
+	}
+}
+
+func TestExtraLarge(t *testing.T) {
+	const N = 100000
+	const offsets = 4
+	ok := "aca9e593cc629cbaa94cd5a07dc029424aad93e5129e5d11f8dcd2f139c16cc0" // sha256sum of "0123456789" * 10000
+	block := make([]byte, N+offsets)
+	c := New()
+	for offset := 0; offset < offsets; offset++ {
+		for i := 0; i < N; i++ {
+			block[offset+i] = '0' + byte(i%10)
+		}
+		for blockSize := 10; blockSize <= N; blockSize *= 10 {
+			blocks := N / blockSize
+			b := block[offset : offset+blockSize]
+			c.Reset()
+			for i := 0; i < blocks; i++ {
+				c.Write(b)
+			}
+			s := fmt.Sprintf("%x", c.Sum(nil))
+			if s != ok {
+				t.Fatalf("sha256 TestExtraLarge offset=%d, blockSize=%d = %s want %s", offset, blockSize, s, ok)
+			}
+		}
+	}
+}
+
 func TestMarshalTypeMismatch(t *testing.T) {
 	h1 := New()
 	h2 := New224()
diff --git a/src/crypto/tls/handshake_client_test.go b/src/crypto/tls/handshake_client_test.go
index 501f9c6755f9e3..3c87916bcf0bb7 100644
--- a/src/crypto/tls/handshake_client_test.go
+++ b/src/crypto/tls/handshake_client_test.go
@@ -852,6 +852,7 @@ func testResumption(t *testing.T, version uint16) {
 		MaxVersion:   version,
 		CipherSuites: []uint16{TLS_RSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA},
 		Certificates: testConfig.Certificates,
+		Time:         testTime,
 	}
 
 	issuer, err := x509.ParseCertificate(testRSACertificateIssuer)
@@ -868,6 +869,7 @@ func testResumption(t *testing.T, version uint16) {
 		ClientSessionCache: NewLRUClientSessionCache(32),
 		RootCAs:            rootCAs,
 		ServerName:         "example.golang",
+		Time:               testTime,
 	}
 
 	testResumeState := func(test string, didResume bool) {
@@ -914,7 +916,7 @@ func testResumption(t *testing.T, version uint16) {
 
 	// An old session ticket is replaced with a ticket encrypted with a fresh key.
 	ticket = getTicket()
-	serverConfig.Time = func() time.Time { return time.Now().Add(24*time.Hour + time.Minute) }
+	serverConfig.Time = func() time.Time { return testTime().Add(24*time.Hour + time.Minute) }
 	testResumeState("ResumeWithOldTicket", true)
 	if bytes.Equal(ticket, getTicket()) {
 		t.Fatal("old first ticket matches the fresh one")
@@ -922,13 +924,13 @@ func testResumption(t *testing.T, version uint16) {
 
 	// Once the session master secret is expired, a full handshake should occur.
 	ticket = getTicket()
-	serverConfig.Time = func() time.Time { return time.Now().Add(24*8*time.Hour + time.Minute) }
+	serverConfig.Time = func() time.Time { return testTime().Add(24*8*time.Hour + time.Minute) }
 	testResumeState("ResumeWithExpiredTicket", false)
 	if bytes.Equal(ticket, getTicket()) {
 		t.Fatal("expired first ticket matches the fresh one")
 	}
 
-	serverConfig.Time = func() time.Time { return time.Now() } // reset the time back
+	serverConfig.Time = testTime // reset the time back
 	key1 := randomKey()
 	serverConfig.SetSessionTicketKeys([][32]byte{key1})
 
@@ -945,11 +947,11 @@ func testResumption(t *testing.T, version uint16) {
 	testResumeState("KeyChangeFinish", true)
 
 	// Age the session ticket a bit, but not yet expired.
-	serverConfig.Time = func() time.Time { return time.Now().Add(24*time.Hour + time.Minute) }
+	serverConfig.Time = func() time.Time { return testTime().Add(24*time.Hour + time.Minute) }
 	testResumeState("OldSessionTicket", true)
 	ticket = getTicket()
 	// Expire the session ticket, which would force a full handshake.
-	serverConfig.Time = func() time.Time { return time.Now().Add(24*8*time.Hour + time.Minute) }
+	serverConfig.Time = func() time.Time { return testTime().Add(24*8*time.Hour + 2*time.Minute) }
 	testResumeState("ExpiredSessionTicket", false)
 	if bytes.Equal(ticket, getTicket()) {
 		t.Fatal("new ticket wasn't provided after old ticket expired")
@@ -957,7 +959,7 @@ func testResumption(t *testing.T, version uint16) {
 
 	// Age the session ticket a bit at a time, but don't expire it.
 	d := 0 * time.Hour
-	serverConfig.Time = func() time.Time { return time.Now().Add(d) }
+	serverConfig.Time = func() time.Time { return testTime().Add(d) }
 	deleteTicket()
 	testResumeState("GetFreshSessionTicket", false)
 	for i := 0; i < 13; i++ {
@@ -968,7 +970,7 @@ func testResumption(t *testing.T, version uint16) {
 	// handshake occurs for TLS 1.2. Resumption should still occur for
 	// TLS 1.3 since the client should be using a fresh ticket sent over
 	// by the server.
-	d += 12 * time.Hour
+	d += 12*time.Hour + time.Minute
 	if version == VersionTLS13 {
 		testResumeState("ExpiredSessionTicket", true)
 	} else {
@@ -984,6 +986,7 @@ func testResumption(t *testing.T, version uint16) {
 		MaxVersion:   version,
 		CipherSuites: []uint16{TLS_RSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA},
 		Certificates: testConfig.Certificates,
+		Time:         testTime,
 	}
 	serverConfig.SetSessionTicketKeys([][32]byte{key2})
 
@@ -1009,6 +1012,7 @@ func testResumption(t *testing.T, version uint16) {
 			CurvePreferences: []CurveID{CurveP521, CurveP384, CurveP256},
 			MaxVersion:       version,
 			Certificates:     testConfig.Certificates,
+			Time:             testTime,
 		}
 		testResumeState("InitialHandshake", false)
 		testResumeState("WithHelloRetryRequest", true)
@@ -1018,6 +1022,7 @@ func testResumption(t *testing.T, version uint16) {
 			MaxVersion:   version,
 			CipherSuites: []uint16{TLS_RSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA},
 			Certificates: testConfig.Certificates,
+			Time:         testTime,
 		}
 	}
 
@@ -1736,6 +1741,7 @@ func testVerifyConnection(t *testing.T, version uint16) {
 		serverConfig := &Config{
 			MaxVersion:   version,
 			Certificates: []Certificate{testConfig.Certificates[0]},
+			Time:         testTime,
 			ClientCAs:    rootCAs,
 			NextProtos:   []string{"protocol1"},
 		}
@@ -1749,6 +1755,7 @@ func testVerifyConnection(t *testing.T, version uint16) {
 			RootCAs:            rootCAs,
 			ServerName:         "example.golang",
 			Certificates:       []Certificate{testConfig.Certificates[0]},
+			Time:               testTime,
 			NextProtos:         []string{"protocol1"},
 		}
 		test.configureClient(clientConfig, &clientCalled)
@@ -1791,8 +1798,6 @@ func testVerifyPeerCertificate(t *testing.T, version uint16) {
 	rootCAs := x509.NewCertPool()
 	rootCAs.AddCert(issuer)
 
-	now := func() time.Time { return time.Unix(1476984729, 0) }
-
 	sentinelErr := errors.New("TestVerifyPeerCertificate")
 
 	verifyPeerCertificateCallback := func(called *bool, rawCerts [][]byte, validatedChains [][]*x509.Certificate) error {
@@ -2038,7 +2043,7 @@ func testVerifyPeerCertificate(t *testing.T, version uint16) {
 			config.ServerName = "example.golang"
 			config.ClientAuth = RequireAndVerifyClientCert
 			config.ClientCAs = rootCAs
-			config.Time = now
+			config.Time = testTime
 			config.MaxVersion = version
 			config.Certificates = make([]Certificate, 1)
 			config.Certificates[0].Certificate = [][]byte{testRSACertificate}
@@ -2055,7 +2060,7 @@ func testVerifyPeerCertificate(t *testing.T, version uint16) {
 		config := testConfig.Clone()
 		config.ServerName = "example.golang"
 		config.RootCAs = rootCAs
-		config.Time = now
+		config.Time = testTime
 		config.MaxVersion = version
 		test.configureClient(config, &clientCalled)
 		clientErr := Client(c, config).Handshake()
@@ -2368,7 +2373,7 @@ func testGetClientCertificate(t *testing.T, version uint16) {
 		serverConfig.RootCAs = x509.NewCertPool()
 		serverConfig.RootCAs.AddCert(issuer)
 		serverConfig.ClientCAs = serverConfig.RootCAs
-		serverConfig.Time = func() time.Time { return time.Unix(1476984729, 0) }
+		serverConfig.Time = testTime
 		serverConfig.MaxVersion = version
 
 		clientConfig := testConfig.Clone()
@@ -2539,6 +2544,7 @@ func testResumptionKeepsOCSPAndSCT(t *testing.T, ver uint16) {
 		ClientSessionCache: NewLRUClientSessionCache(32),
 		ServerName:         "example.golang",
 		RootCAs:            roots,
+		Time:               testTime,
 	}
 	serverConfig := testConfig.Clone()
 	serverConfig.MaxVersion = ver
diff --git a/src/crypto/tls/handshake_server_test.go b/src/crypto/tls/handshake_server_test.go
index 94d3d0f6dc87bc..bbfe44bd97daa2 100644
--- a/src/crypto/tls/handshake_server_test.go
+++ b/src/crypto/tls/handshake_server_test.go
@@ -501,6 +501,7 @@ func testCrossVersionResume(t *testing.T, version uint16) {
 	serverConfig := &Config{
 		CipherSuites: []uint16{TLS_RSA_WITH_AES_128_CBC_SHA},
 		Certificates: testConfig.Certificates,
+		Time:         testTime,
 	}
 	clientConfig := &Config{
 		CipherSuites:       []uint16{TLS_RSA_WITH_AES_128_CBC_SHA},
@@ -508,6 +509,7 @@ func testCrossVersionResume(t *testing.T, version uint16) {
 		ClientSessionCache: NewLRUClientSessionCache(1),
 		ServerName:         "servername",
 		MinVersion:         VersionTLS12,
+		Time:               testTime,
 	}
 
 	// Establish a session at TLS 1.3.
diff --git a/src/crypto/tls/handshake_test.go b/src/crypto/tls/handshake_test.go
index bc3d23d5adc24e..803aa736578f8c 100644
--- a/src/crypto/tls/handshake_test.go
+++ b/src/crypto/tls/handshake_test.go
@@ -491,9 +491,10 @@ func testHandshake(t *testing.T, clientConfig, serverConfig *Config) (serverStat
 		if got := string(buf); got != sentinel {
 			t.Errorf("read %q from TLS connection, but expected %q", got, sentinel)
 		}
-		if err := cli.Close(); err != nil {
-			t.Errorf("failed to call cli.Close: %v", err)
-		}
+		// We discard the error because after ReadAll returns the server must
+		// have already closed the connection. Sending data (the closeNotify
+		// alert) can cause a reset, that will make Close return an error.
+		cli.Close()
 	}()
 	server := Server(s, serverConfig)
 	err = server.Handshake()
@@ -518,6 +519,11 @@ func fromHex(s string) []byte {
 	return b
 }
 
+// testTime is 2016-10-20T17:32:09.000Z, which is within the validity period of
+// [testRSACertificate], [testRSACertificateIssuer], [testRSA2048Certificate],
+// [testRSA2048CertificateIssuer], and [testECDSACertificate].
+var testTime = func() time.Time { return time.Unix(1476984729, 0) }
+
 var testRSACertificate = fromHex("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")
 
 var testRSACertificateIssuer = fromHex("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")
diff --git a/src/crypto/tls/tls_test.go b/src/crypto/tls/tls_test.go
index fc5040635fbbf7..13c5ddced2cddb 100644
--- a/src/crypto/tls/tls_test.go
+++ b/src/crypto/tls/tls_test.go
@@ -1112,8 +1112,6 @@ func TestConnectionState(t *testing.T) {
 	rootCAs := x509.NewCertPool()
 	rootCAs.AddCert(issuer)
 
-	now := func() time.Time { return time.Unix(1476984729, 0) }
-
 	const alpnProtocol = "golang"
 	const serverName = "example.golang"
 	var scts = [][]byte{[]byte("dummy sct 1"), []byte("dummy sct 2")}
@@ -1129,7 +1127,7 @@ func TestConnectionState(t *testing.T) {
 		}
 		t.Run(name, func(t *testing.T) {
 			config := &Config{
-				Time:         now,
+				Time:         testTime,
 				Rand:         zeroSource{},
 				Certificates: make([]Certificate, 1),
 				MaxVersion:   v,
@@ -1760,7 +1758,7 @@ func testVerifyCertificates(t *testing.T, version uint16) {
 			var serverVerifyPeerCertificates, clientVerifyPeerCertificates bool
 
 			clientConfig := testConfig.Clone()
-			clientConfig.Time = func() time.Time { return time.Unix(1476984729, 0) }
+			clientConfig.Time = testTime
 			clientConfig.MaxVersion = version
 			clientConfig.MinVersion = version
 			clientConfig.RootCAs = rootCAs
diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index de774a051093df..c247a9b506bfab 100644
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -1368,8 +1368,8 @@ func (db *DB) conn(ctx context.Context, strategy connReuseStrategy) (*driverConn
 
 			db.waitDuration.Add(int64(time.Since(waitStart)))
 
-			// If we failed to delete it, that means something else
-			// grabbed it and is about to send on it.
+			// If we failed to delete it, that means either the DB was closed or
+			// something else grabbed it and is about to send on it.
 			if !deleted {
 				// TODO(bradfitz): rather than this best effort select, we
 				// should probably start a goroutine to read from req. This best
@@ -3594,6 +3594,7 @@ type connRequestAndIndex struct {
 // and clears the set.
 func (s *connRequestSet) CloseAndRemoveAll() {
 	for _, v := range s.s {
+		*v.curIdx = -1
 		close(v.req)
 	}
 	s.s = nil
diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
index ff65e877a5af6b..110a2bae5bd247 100644
--- a/src/database/sql/sql_test.go
+++ b/src/database/sql/sql_test.go
@@ -4920,6 +4920,17 @@ func TestConnRequestSet(t *testing.T) {
 			t.Error("wasn't random")
 		}
 	})
+	t.Run("close-delete", func(t *testing.T) {
+		reset()
+		ch := make(chan connRequest)
+		dh := s.Add(ch)
+		wantLen(1)
+		s.CloseAndRemoveAll()
+		wantLen(0)
+		if s.Delete(dh) {
+			t.Error("unexpected delete after CloseAndRemoveAll")
+		}
+	})
 }
 
 func BenchmarkConnRequestSet(b *testing.B) {
diff --git a/src/encoding/gob/decode.go b/src/encoding/gob/decode.go
index d178b2b2fb6467..26b5f6d62b631e 100644
--- a/src/encoding/gob/decode.go
+++ b/src/encoding/gob/decode.go
@@ -911,8 +911,11 @@ func (dec *Decoder) decOpFor(wireId typeId, rt reflect.Type, name string, inProg
 var maxIgnoreNestingDepth = 10000
 
 // decIgnoreOpFor returns the decoding op for a field that has no destination.
-func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp, depth int) *decOp {
-	if depth > maxIgnoreNestingDepth {
+func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp) *decOp {
+	// Track how deep we've recursed trying to skip nested ignored fields.
+	dec.ignoreDepth++
+	defer func() { dec.ignoreDepth-- }()
+	if dec.ignoreDepth > maxIgnoreNestingDepth {
 		error_(errors.New("invalid nesting depth"))
 	}
 	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
@@ -938,7 +941,7 @@ func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp,
 			errorf("bad data: undefined type %s", wireId.string())
 		case wire.ArrayT != nil:
 			elemId := wire.ArrayT.Elem
-			elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
+			elemOp := dec.decIgnoreOpFor(elemId, inProgress)
 			op = func(i *decInstr, state *decoderState, value reflect.Value) {
 				state.dec.ignoreArray(state, *elemOp, wire.ArrayT.Len)
 			}
@@ -946,15 +949,15 @@ func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp,
 		case wire.MapT != nil:
 			keyId := dec.wireType[wireId].MapT.Key
 			elemId := dec.wireType[wireId].MapT.Elem
-			keyOp := dec.decIgnoreOpFor(keyId, inProgress, depth+1)
-			elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
+			keyOp := dec.decIgnoreOpFor(keyId, inProgress)
+			elemOp := dec.decIgnoreOpFor(elemId, inProgress)
 			op = func(i *decInstr, state *decoderState, value reflect.Value) {
 				state.dec.ignoreMap(state, *keyOp, *elemOp)
 			}
 
 		case wire.SliceT != nil:
 			elemId := wire.SliceT.Elem
-			elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
+			elemOp := dec.decIgnoreOpFor(elemId, inProgress)
 			op = func(i *decInstr, state *decoderState, value reflect.Value) {
 				state.dec.ignoreSlice(state, *elemOp)
 			}
@@ -1115,7 +1118,7 @@ func (dec *Decoder) compileSingle(remoteId typeId, ut *userTypeInfo) (engine *de
 func (dec *Decoder) compileIgnoreSingle(remoteId typeId) *decEngine {
 	engine := new(decEngine)
 	engine.instr = make([]decInstr, 1) // one item
-	op := dec.decIgnoreOpFor(remoteId, make(map[typeId]*decOp), 0)
+	op := dec.decIgnoreOpFor(remoteId, make(map[typeId]*decOp))
 	ovfl := overflow(dec.typeString(remoteId))
 	engine.instr[0] = decInstr{*op, 0, nil, ovfl}
 	engine.numInstr = 1
@@ -1160,7 +1163,7 @@ func (dec *Decoder) compileDec(remoteId typeId, ut *userTypeInfo) (engine *decEn
 		localField, present := srt.FieldByName(wireField.Name)
 		// TODO(r): anonymous names
 		if !present || !isExported(wireField.Name) {
-			op := dec.decIgnoreOpFor(wireField.Id, make(map[typeId]*decOp), 0)
+			op := dec.decIgnoreOpFor(wireField.Id, make(map[typeId]*decOp))
 			engine.instr[fieldnum] = decInstr{*op, fieldnum, nil, ovfl}
 			continue
 		}
diff --git a/src/encoding/gob/decoder.go b/src/encoding/gob/decoder.go
index c4b60880130787..eae307838e201e 100644
--- a/src/encoding/gob/decoder.go
+++ b/src/encoding/gob/decoder.go
@@ -35,6 +35,8 @@ type Decoder struct {
 	freeList     *decoderState                           // list of free decoderStates; avoids reallocation
 	countBuf     []byte                                  // used for decoding integers while parsing messages
 	err          error
+	// ignoreDepth tracks the depth of recursively parsed ignored fields
+	ignoreDepth int
 }
 
 // NewDecoder returns a new decoder that reads from the [io.Reader].
diff --git a/src/encoding/gob/gobencdec_test.go b/src/encoding/gob/gobencdec_test.go
index ae806fc39a21fc..d30e622aa2cbe7 100644
--- a/src/encoding/gob/gobencdec_test.go
+++ b/src/encoding/gob/gobencdec_test.go
@@ -806,6 +806,8 @@ func TestIgnoreDepthLimit(t *testing.T) {
 	defer func() { maxIgnoreNestingDepth = oldNestingDepth }()
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
+
+	// Nested slice
 	typ := reflect.TypeFor[int]()
 	nested := reflect.ArrayOf(1, typ)
 	for i := 0; i < 100; i++ {
@@ -819,4 +821,16 @@ func TestIgnoreDepthLimit(t *testing.T) {
 	if err := dec.Decode(&output); err == nil || err.Error() != expectedErr {
 		t.Errorf("Decode didn't fail with depth limit of 100: want %q, got %q", expectedErr, err)
 	}
+
+	// Nested struct
+	nested = reflect.StructOf([]reflect.StructField{{Name: "F", Type: typ}})
+	for i := 0; i < 100; i++ {
+		nested = reflect.StructOf([]reflect.StructField{{Name: "F", Type: nested}})
+	}
+	badStruct = reflect.New(reflect.StructOf([]reflect.StructField{{Name: "F", Type: nested}}))
+	enc.Encode(badStruct.Interface())
+	dec = NewDecoder(b)
+	if err := dec.Decode(&output); err == nil || err.Error() != expectedErr {
+		t.Errorf("Decode didn't fail with depth limit of 100: want %q, got %q", expectedErr, err)
+	}
 }
diff --git a/src/go/build/constraint/expr.go b/src/go/build/constraint/expr.go
index e59012361bef6d..0f05f8db6a48cb 100644
--- a/src/go/build/constraint/expr.go
+++ b/src/go/build/constraint/expr.go
@@ -16,6 +16,10 @@ import (
 	"unicode/utf8"
 )
 
+// maxSize is a limit used to control the complexity of expressions, in order
+// to prevent stack exhaustion issues due to recursion.
+const maxSize = 1000
+
 // An Expr is a build tag constraint expression.
 // The underlying concrete type is *[AndExpr], *[OrExpr], *[NotExpr], or *[TagExpr].
 type Expr interface {
@@ -151,7 +155,7 @@ func Parse(line string) (Expr, error) {
 		return parseExpr(text)
 	}
 	if text, ok := splitPlusBuild(line); ok {
-		return parsePlusBuildExpr(text), nil
+		return parsePlusBuildExpr(text)
 	}
 	return nil, errNotConstraint
 }
@@ -201,6 +205,8 @@ type exprParser struct {
 	tok   string // last token read
 	isTag bool
 	pos   int // position (start) of last token
+
+	size int
 }
 
 // parseExpr parses a boolean build tag expression.
@@ -249,6 +255,10 @@ func (p *exprParser) and() Expr {
 // On entry, the next input token has not yet been lexed.
 // On exit, the next input token has been lexed and is in p.tok.
 func (p *exprParser) not() Expr {
+	p.size++
+	if p.size > maxSize {
+		panic(&SyntaxError{Offset: p.pos, Err: "build expression too large"})
+	}
 	p.lex()
 	if p.tok == "!" {
 		p.lex()
@@ -388,7 +398,13 @@ func splitPlusBuild(line string) (expr string, ok bool) {
 }
 
 // parsePlusBuildExpr parses a legacy build tag expression (as used with “// +build”).
-func parsePlusBuildExpr(text string) Expr {
+func parsePlusBuildExpr(text string) (Expr, error) {
+	// Only allow up to 100 AND/OR operators for "old" syntax.
+	// This is much less than the limit for "new" syntax,
+	// but uses of old syntax were always very simple.
+	const maxOldSize = 100
+	size := 0
+
 	var x Expr
 	for _, clause := range strings.Fields(text) {
 		var y Expr
@@ -414,19 +430,25 @@ func parsePlusBuildExpr(text string) Expr {
 			if y == nil {
 				y = z
 			} else {
+				if size++; size > maxOldSize {
+					return nil, errComplex
+				}
 				y = and(y, z)
 			}
 		}
 		if x == nil {
 			x = y
 		} else {
+			if size++; size > maxOldSize {
+				return nil, errComplex
+			}
 			x = or(x, y)
 		}
 	}
 	if x == nil {
 		x = tag("ignore")
 	}
-	return x
+	return x, nil
 }
 
 // isValidTag reports whether the word is a valid build tag.
diff --git a/src/go/build/constraint/expr_test.go b/src/go/build/constraint/expr_test.go
index 15d189012efb7d..ac38ba69294930 100644
--- a/src/go/build/constraint/expr_test.go
+++ b/src/go/build/constraint/expr_test.go
@@ -222,7 +222,7 @@ var parsePlusBuildExprTests = []struct {
 func TestParsePlusBuildExpr(t *testing.T) {
 	for i, tt := range parsePlusBuildExprTests {
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
-			x := parsePlusBuildExpr(tt.in)
+			x, _ := parsePlusBuildExpr(tt.in)
 			if x.String() != tt.x.String() {
 				t.Errorf("parsePlusBuildExpr(%q):\nhave %v\nwant %v", tt.in, x, tt.x)
 			}
@@ -319,3 +319,66 @@ func TestPlusBuildLines(t *testing.T) {
 		})
 	}
 }
+
+func TestSizeLimits(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		expr string
+	}{
+		{
+			name: "go:build or limit",
+			expr: "//go:build " + strings.Repeat("a || ", maxSize+2),
+		},
+		{
+			name: "go:build and limit",
+			expr: "//go:build " + strings.Repeat("a && ", maxSize+2),
+		},
+		{
+			name: "go:build and depth limit",
+			expr: "//go:build " + strings.Repeat("(a &&", maxSize+2),
+		},
+		{
+			name: "go:build or depth limit",
+			expr: "//go:build " + strings.Repeat("(a ||", maxSize+2),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := Parse(tc.expr)
+			if err == nil {
+				t.Error("expression did not trigger limit")
+			} else if syntaxErr, ok := err.(*SyntaxError); !ok || syntaxErr.Err != "build expression too large" {
+				if !ok {
+					t.Errorf("unexpected error: %v", err)
+				} else {
+					t.Errorf("unexpected syntax error: %s", syntaxErr.Err)
+				}
+			}
+		})
+	}
+}
+
+func TestPlusSizeLimits(t *testing.T) {
+	maxOldSize := 100
+	for _, tc := range []struct {
+		name string
+		expr string
+	}{
+		{
+			name: "+build or limit",
+			expr: "// +build " + strings.Repeat("a ", maxOldSize+2),
+		},
+		{
+			name: "+build and limit",
+			expr: "// +build " + strings.Repeat("a,", maxOldSize+2),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := Parse(tc.expr)
+			if err == nil {
+				t.Error("expression did not trigger limit")
+			} else if err != errComplex {
+				t.Errorf("unexpected error: got %q, want %q", err, errComplex)
+			}
+		})
+	}
+}
diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index 17808b366f092d..f268dea1a6f9cd 100644
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -1676,6 +1676,8 @@ func (p *parser) parseElementList() (list []ast.Expr) {
 }
 
 func (p *parser) parseLiteralValue(typ ast.Expr) ast.Expr {
+	defer decNestLev(incNestLev(p))
+
 	if p.trace {
 		defer un(trace(p, "LiteralValue"))
 	}
diff --git a/src/go/parser/parser_test.go b/src/go/parser/parser_test.go
index eea743c2b5b261..2c33e9ef314ad3 100644
--- a/src/go/parser/parser_test.go
+++ b/src/go/parser/parser_test.go
@@ -598,10 +598,11 @@ var parseDepthTests = []struct {
 	{name: "chan2", format: "package main; var x «<-chan »int"},
 	{name: "interface", format: "package main; var x «interface { M() «int» }»", scope: true, scopeMultiplier: 2}, // Scopes: InterfaceType, FuncType
 	{name: "map", format: "package main; var x «map[int]»int"},
-	{name: "slicelit", format: "package main; var x = «[]any{«»}»", parseMultiplier: 2},             // Parser nodes: UnaryExpr, CompositeLit
-	{name: "arraylit", format: "package main; var x = «[1]any{«nil»}»", parseMultiplier: 2},         // Parser nodes: UnaryExpr, CompositeLit
-	{name: "structlit", format: "package main; var x = «struct{x any}{«nil»}»", parseMultiplier: 2}, // Parser nodes: UnaryExpr, CompositeLit
-	{name: "maplit", format: "package main; var x = «map[int]any{1:«nil»}»", parseMultiplier: 2},    // Parser nodes: CompositeLit, KeyValueExpr
+	{name: "slicelit", format: "package main; var x = []any{«[]any{«»}»}", parseMultiplier: 3},      // Parser nodes: UnaryExpr, CompositeLit
+	{name: "arraylit", format: "package main; var x = «[1]any{«nil»}»", parseMultiplier: 3},         // Parser nodes: UnaryExpr, CompositeLit
+	{name: "structlit", format: "package main; var x = «struct{x any}{«nil»}»", parseMultiplier: 3}, // Parser nodes: UnaryExpr, CompositeLit
+	{name: "maplit", format: "package main; var x = «map[int]any{1:«nil»}»", parseMultiplier: 3},    // Parser nodes: CompositeLit, KeyValueExpr
+	{name: "element", format: "package main; var x = struct{x any}{x: «{«»}»}"},
 	{name: "dot", format: "package main; var x = «x.»x"},
 	{name: "index", format: "package main; var x = x«[1]»"},
 	{name: "slice", format: "package main; var x = x«[1:2]»"},
diff --git a/src/go/types/alias.go b/src/go/types/alias.go
index af43471a324176..7adb3deb58bbc7 100644
--- a/src/go/types/alias.go
+++ b/src/go/types/alias.go
@@ -137,10 +137,10 @@ func (check *Checker) newAlias(obj *TypeName, rhs Type) *Alias {
 // newAliasInstance creates a new alias instance for the given origin and type
 // arguments, recording pos as the position of its synthetic object (for error
 // reporting).
-func (check *Checker) newAliasInstance(pos token.Pos, orig *Alias, targs []Type, ctxt *Context) *Alias {
+func (check *Checker) newAliasInstance(pos token.Pos, orig *Alias, targs []Type, expanding *Named, ctxt *Context) *Alias {
 	assert(len(targs) > 0)
 	obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
-	rhs := check.subst(pos, orig.fromRHS, makeSubstMap(orig.TypeParams().list(), targs), nil, ctxt)
+	rhs := check.subst(pos, orig.fromRHS, makeSubstMap(orig.TypeParams().list(), targs), expanding, ctxt)
 	res := check.newAlias(obj, rhs)
 	res.orig = orig
 	res.tparams = orig.tparams
diff --git a/src/go/types/api_test.go b/src/go/types/api_test.go
index beed94f3557996..a7aa6488028ecd 100644
--- a/src/go/types/api_test.go
+++ b/src/go/types/api_test.go
@@ -2904,22 +2904,48 @@ func TestFileVersions(t *testing.T) {
 		fileVersion string
 		wantVersion string
 	}{
-		{"", "", ""},                   // no versions specified
-		{"go1.19", "", "go1.19"},       // module version specified
-		{"", "go1.20", ""},             // file upgrade ignored
-		{"go1.19", "go1.20", "go1.20"}, // file upgrade permitted
-		{"go1.20", "go1.19", "go1.20"}, // file downgrade not permitted
-		{"go1.21", "go1.19", "go1.19"}, // file downgrade permitted (module version is >= go1.21)
+		{"", "", ""},                    // no versions specified
+		{"go1.19", "", "go1.19"},        // module version specified
+		{"", "go1.20", "go1.21"},        // file version specified below minimum of 1.21
+		{"go1", "", "go1"},              // no file version specified
+		{"go1", "goo1.22", "go1"},       // invalid file version specified
+		{"go1", "go1.19", "go1.21"},     // file version specified below minimum of 1.21
+		{"go1", "go1.20", "go1.21"},     // file version specified below minimum of 1.21
+		{"go1", "go1.21", "go1.21"},     // file version specified at 1.21
+		{"go1", "go1.22", "go1.22"},     // file version specified above 1.21
+		{"go1.19", "", "go1.19"},        // no file version specified
+		{"go1.19", "goo1.22", "go1.19"}, // invalid file version specified
+		{"go1.19", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.19", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.19", "go1.22", "go1.22"},  // file version specified above 1.21
+		{"go1.20", "", "go1.20"},        // no file version specified
+		{"go1.20", "goo1.22", "go1.20"}, // invalid file version specified
+		{"go1.20", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.20", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.20", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.20", "go1.22", "go1.22"},  // file version specified above 1.21
+		{"go1.21", "", "go1.21"},        // no file version specified
+		{"go1.21", "goo1.22", "go1.21"}, // invalid file version specified
+		{"go1.21", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.21", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.21", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.21", "go1.22", "go1.22"},  // file version specified above 1.21
+		{"go1.22", "", "go1.22"},        // no file version specified
+		{"go1.22", "goo1.22", "go1.22"}, // invalid file version specified
+		{"go1.22", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.22", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
+		{"go1.22", "go1.21", "go1.21"},  // file version specified at 1.21
+		{"go1.22", "go1.22", "go1.22"},  // file version specified above 1.21
 
 		// versions containing release numbers
 		// (file versions containing release numbers are considered invalid)
 		{"go1.19.0", "", "go1.19.0"},         // no file version specified
-		{"go1.20", "go1.20.1", "go1.20"},     // file upgrade ignored
-		{"go1.20.1", "go1.20", "go1.20.1"},   // file upgrade ignored
-		{"go1.20.1", "go1.21", "go1.21"},     // file upgrade permitted
-		{"go1.20.1", "go1.19", "go1.20.1"},   // file downgrade not permitted
-		{"go1.21.1", "go1.19.1", "go1.21.1"}, // file downgrade not permitted (invalid file version)
-		{"go1.21.1", "go1.19", "go1.19"},     // file downgrade permitted (module version is >= go1.21)
+		{"go1.20.1", "go1.19.1", "go1.20.1"}, // invalid file version
+		{"go1.20.1", "go1.21.1", "go1.20.1"}, // invalid file version
+		{"go1.21.1", "go1.19.1", "go1.21.1"}, // invalid file version
+		{"go1.21.1", "go1.21.1", "go1.21.1"}, // invalid file version
+		{"go1.22.1", "go1.19.1", "go1.22.1"}, // invalid file version
+		{"go1.22.1", "go1.21.1", "go1.22.1"}, // invalid file version
 	} {
 		var src string
 		if test.fileVersion != "" {
diff --git a/src/go/types/check.go b/src/go/types/check.go
index 1a5a41a3bb4b99..8a729094961fe2 100644
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -349,7 +349,6 @@ func (check *Checker) initFiles(files []*ast.File) {
 		check.errorf(files[0], TooNew, "package requires newer Go version %v (application built with %v)",
 			check.version, go_current)
 	}
-	downgradeOk := check.version.cmp(go1_21) >= 0
 
 	// determine Go version for each file
 	for _, file := range check.files {
@@ -358,33 +357,19 @@ func (check *Checker) initFiles(files []*ast.File) {
 		// unlike file versions which are Go language versions only, if valid.)
 		v := check.conf.GoVersion
 
-		fileVersion := asGoVersion(file.GoVersion)
-		if fileVersion.isValid() {
-			// use the file version, if applicable
-			// (file versions are either the empty string or of the form go1.dd)
-			if pkgVersionOk {
-				cmp := fileVersion.cmp(check.version)
-				// Go 1.21 introduced the feature of setting the go.mod
-				// go line to an early version of Go and allowing //go:build lines
-				// to “upgrade” (cmp > 0) the Go version in a given file.
-				// We can do that backwards compatibly.
-				//
-				// Go 1.21 also introduced the feature of allowing //go:build lines
-				// to “downgrade” (cmp < 0) the Go version in a given file.
-				// That can't be done compatibly in general, since before the
-				// build lines were ignored and code got the module's Go version.
-				// To work around this, downgrades are only allowed when the
-				// module's Go version is Go 1.21 or later.
-				//
-				// If there is no valid check.version, then we don't really know what
-				// Go version to apply.
-				// Legacy tools may do this, and they historically have accepted everything.
-				// Preserve that behavior by ignoring //go:build constraints entirely in that
-				// case (!pkgVersionOk).
-				if cmp > 0 || cmp < 0 && downgradeOk {
-					v = file.GoVersion
-				}
-			}
+		// If the file specifies a version, use max(fileVersion, go1.21).
+		if fileVersion := asGoVersion(file.GoVersion); fileVersion.isValid() {
+			// Go 1.21 introduced the feature of setting the go.mod
+			// go line to an early version of Go and allowing //go:build lines
+			// to set the Go version in a given file. Versions Go 1.21 and later
+			// can be set backwards compatibly as that was the first version
+			// files with go1.21 or later build tags could be built with.
+			//
+			// Set the version to max(fileVersion, go1.21): That will allow a
+			// downgrade to a version before go1.22, where the for loop semantics
+			// change was made, while being backwards compatible with versions of
+			// go before the new //go:build semantics were introduced.
+			v = string(versionMax(fileVersion, go1_21))
 
 			// Report a specific error for each tagged file that's too new.
 			// (Normally the build system will have filtered files by version,
@@ -399,6 +384,13 @@ func (check *Checker) initFiles(files []*ast.File) {
 	}
 }
 
+func versionMax(a, b goVersion) goVersion {
+	if a.cmp(b) < 0 {
+		return b
+	}
+	return a
+}
+
 // A bailout panic is used for early termination.
 type bailout struct{}
 
diff --git a/src/go/types/instantiate.go b/src/go/types/instantiate.go
index 7bec790b5586ad..0435f2bf261647 100644
--- a/src/go/types/instantiate.go
+++ b/src/go/types/instantiate.go
@@ -14,6 +14,7 @@ import (
 	"errors"
 	"fmt"
 	"go/token"
+	"internal/buildcfg"
 	. "internal/types/errors"
 )
 
@@ -129,8 +130,9 @@ func (check *Checker) instance(pos token.Pos, orig genericType, targs []Type, ex
 		res = check.newNamedInstance(pos, orig, targs, expanding) // substituted lazily
 
 	case *Alias:
-		// TODO(gri) is this correct?
-		assert(expanding == nil) // Alias instances cannot be reached from Named types
+		if !buildcfg.Experiment.AliasTypeParams {
+			assert(expanding == nil) // Alias instances cannot be reached from Named types
+		}
 
 		tparams := orig.TypeParams()
 		// TODO(gri) investigate if this is needed (type argument and parameter count seem to be correct here)
@@ -141,7 +143,7 @@ func (check *Checker) instance(pos token.Pos, orig genericType, targs []Type, ex
 			return orig // nothing to do (minor optimization)
 		}
 
-		return check.newAliasInstance(pos, orig, targs, ctxt)
+		return check.newAliasInstance(pos, orig, targs, expanding, ctxt)
 
 	case *Signature:
 		assert(expanding == nil) // function instances cannot be reached from Named types
diff --git a/src/go/types/issues_test.go b/src/go/types/issues_test.go
index 3f459d3883017e..da0c0c1255b63e 100644
--- a/src/go/types/issues_test.go
+++ b/src/go/types/issues_test.go
@@ -1131,3 +1131,23 @@ func f(x int) {
 		t.Errorf("got: %s want: %s", got, want)
 	}
 }
+
+func TestIssue68877(t *testing.T) {
+	const src = `
+package p
+
+type (
+	S struct{}
+	A = S
+	T A
+)`
+
+	t.Setenv("GODEBUG", "gotypesalias=1")
+	pkg := mustTypecheck(src, nil, nil)
+	T := pkg.Scope().Lookup("T").(*TypeName)
+	got := T.String() // this must not panic (was issue)
+	const want = "type p.T struct{}"
+	if got != want {
+		t.Errorf("got %s, want %s", got, want)
+	}
+}
diff --git a/src/go/types/named.go b/src/go/types/named.go
index b44fa9d788c345..d55b023812d108 100644
--- a/src/go/types/named.go
+++ b/src/go/types/named.go
@@ -285,7 +285,7 @@ func (t *Named) cleanup() {
 		if t.TypeArgs().Len() == 0 {
 			panic("nil underlying")
 		}
-	case *Named:
+	case *Named, *Alias:
 		t.under() // t.under may add entries to check.cleaners
 	}
 	t.check = nil
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 5ad2ff61eb1d30..6be106d3aa99d6 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -118,7 +118,7 @@ func (subst *subster) typ(typ Type) Type {
 		// that has a type argument for it.
 		targs, updated := subst.typeList(t.TypeArgs().list())
 		if updated {
-			return subst.check.newAliasInstance(subst.pos, t.orig, targs, subst.ctxt)
+			return subst.check.newAliasInstance(subst.pos, t.orig, targs, subst.expanding, subst.ctxt)
 		}
 
 	case *Array:
diff --git a/src/go/types/typeset.go b/src/go/types/typeset.go
index d280bf2f5ff5cf..a1d7e6cc994e48 100644
--- a/src/go/types/typeset.go
+++ b/src/go/types/typeset.go
@@ -134,8 +134,8 @@ func (s *_TypeSet) underIs(f func(Type) bool) bool {
 	}
 	for _, t := range s.terms {
 		assert(t.typ != nil)
-		// x == under(x) for ~x terms
-		u := t.typ
+		// Unalias(x) == under(x) for ~x terms
+		u := Unalias(t.typ)
 		if !t.tilde {
 			u = under(u)
 		}
diff --git a/src/internal/abi/type.go b/src/internal/abi/type.go
index 786bafff723c96..b8eefe0da8dbba 100644
--- a/src/internal/abi/type.go
+++ b/src/internal/abi/type.go
@@ -177,6 +177,15 @@ func TypeOf(a any) *Type {
 	return (*Type)(NoEscape(unsafe.Pointer(eface.Type)))
 }
 
+// TypeFor returns the abi.Type for a type parameter.
+func TypeFor[T any]() *Type {
+	var v T
+	if t := TypeOf(v); t != nil {
+		return t // optimize for T being a non-interface kind
+	}
+	return TypeOf((*T)(nil)).Elem() // only for an interface kind
+}
+
 func (t *Type) Kind() Kind { return t.Kind_ & KindMask }
 
 func (t *Type) HasName() bool {
diff --git a/src/internal/poll/sendfile_bsd.go b/src/internal/poll/sendfile_bsd.go
index 669df94cc12e0d..d1023d4ebb9938 100644
--- a/src/internal/poll/sendfile_bsd.go
+++ b/src/internal/poll/sendfile_bsd.go
@@ -32,28 +32,46 @@ func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error,
 		if int64(n) > remain {
 			n = int(remain)
 		}
+		m := n
 		pos1 := pos
 		n, err = syscall.Sendfile(dst, src, &pos1, n)
 		if n > 0 {
 			pos += int64(n)
 			written += int64(n)
 			remain -= int64(n)
+			// (n, nil) indicates that sendfile(2) has transferred
+			// the exact number of bytes we requested, or some unretryable
+			// error have occurred with partial bytes sent. Either way, we
+			// don't need to go through the following logic to check EINTR
+			// or fell into dstFD.pd.waitWrite, just continue to send the
+			// next chunk or break the loop.
+			if n == m {
+				continue
+			} else if err != syscall.EAGAIN &&
+				err != syscall.EINTR &&
+				err != syscall.EBUSY {
+				// Particularly, EPIPE. Errors like that would normally lead
+				// the subsequent sendfile(2) call to (-1, EBADF).
+				break
+			}
+		} else if err != syscall.EAGAIN && err != syscall.EINTR {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile), and other errors.
+			// We should end the loop when there is no error
+			// returned from sendfile(2) or it is not a retryable error.
+			break
 		}
 		if err == syscall.EINTR {
 			continue
 		}
-		// This includes syscall.ENOSYS (no kernel
-		// support) and syscall.EINVAL (fd types which
-		// don't implement sendfile), and other errors.
-		// We should end the loop when there is no error
-		// returned from sendfile(2) or it is not a retryable error.
-		if err != syscall.EAGAIN {
-			break
-		}
 		if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
 			break
 		}
 	}
-	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
+	if err == syscall.EAGAIN {
+		err = nil
+	}
+	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL && err != syscall.EOPNOTSUPP && err != syscall.ENOTSUP)
 	return
 }
diff --git a/src/internal/poll/sendfile_linux.go b/src/internal/poll/sendfile_linux.go
index d1c4d5c0d3d34d..1c4130d45da89c 100644
--- a/src/internal/poll/sendfile_linux.go
+++ b/src/internal/poll/sendfile_linux.go
@@ -50,6 +50,9 @@ func SendFile(dstFD *FD, src int, remain int64) (written int64, err error, handl
 			break
 		}
 	}
+	if err == syscall.EAGAIN {
+		err = nil
+	}
 	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
 	return
 }
diff --git a/src/internal/poll/sendfile_solaris.go b/src/internal/poll/sendfile_solaris.go
index ec675833a225dc..b7c3f81a1efdcd 100644
--- a/src/internal/poll/sendfile_solaris.go
+++ b/src/internal/poll/sendfile_solaris.go
@@ -61,6 +61,9 @@ func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error,
 			break
 		}
 	}
+	if err == syscall.EAGAIN {
+		err = nil
+	}
 	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
 	return
 }
diff --git a/src/internal/types/testdata/check/go1_20_19.go b/src/internal/types/testdata/check/go1_20_19.go
index 08365a7cfb564d..e040d396c7808b 100644
--- a/src/internal/types/testdata/check/go1_20_19.go
+++ b/src/internal/types/testdata/check/go1_20_19.go
@@ -14,4 +14,4 @@ type Slice []byte
 type Array [8]byte
 
 var s Slice
-var p = (Array)(s /* ok because Go 1.20 ignored the //go:build go1.19 */)
+var p = (Array)(s /* ok because file versions below go1.21 set the langage version to go1.21 */)
diff --git a/src/internal/types/testdata/check/go1_21_19.go b/src/internal/types/testdata/check/go1_21_19.go
index 2acd25865d4b69..5866033eafe6f8 100644
--- a/src/internal/types/testdata/check/go1_21_19.go
+++ b/src/internal/types/testdata/check/go1_21_19.go
@@ -14,4 +14,4 @@ type Slice []byte
 type Array [8]byte
 
 var s Slice
-var p = (Array)(s /* ERROR "requires go1.20 or later" */)
+var p = (Array)(s /* ok because file versions below go1.21 set the langage version to go1.21 */)
diff --git a/src/internal/types/testdata/check/go1_21_22.go b/src/internal/types/testdata/check/go1_21_22.go
new file mode 100644
index 00000000000000..3939b7b1d868c0
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_21_22.go
@@ -0,0 +1,16 @@
+// -lang=go1.21
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+//go:build go1.22
+
+package p
+
+func f() {
+	for _ = range /* ok because of upgrade to 1.22 */ 10 {
+	}
+}
diff --git a/src/internal/types/testdata/check/go1_22_21.go b/src/internal/types/testdata/check/go1_22_21.go
new file mode 100644
index 00000000000000..f910ecb59cbc78
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_22_21.go
@@ -0,0 +1,16 @@
+// -lang=go1.22
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+//go:build go1.21
+
+package p
+
+func f() {
+	for _ = range 10 /* ERROR "requires go1.22 or later" */ {
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue66285.go b/src/internal/types/testdata/fixedbugs/issue66285.go
index 9811fec3f35549..4af76f05da8e41 100644
--- a/src/internal/types/testdata/fixedbugs/issue66285.go
+++ b/src/internal/types/testdata/fixedbugs/issue66285.go
@@ -1,14 +1,9 @@
-// -lang=go1.21
+// -lang=go1.13
 
 // Copyright 2024 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Note: Downgrading to go1.13 requires at least go1.21,
-//       hence the need for -lang=go1.21 at the top.
-
-//go:build go1.13
-
 package p
 
 import "io"
diff --git a/src/internal/types/testdata/fixedbugs/issue68903.go b/src/internal/types/testdata/fixedbugs/issue68903.go
new file mode 100644
index 00000000000000..b1369aa0f6faa7
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue68903.go
@@ -0,0 +1,24 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type A = [4]int
+type B = map[string]interface{}
+
+func _[T ~A](x T) {
+	_ = len(x)
+}
+
+func _[U ~A](x U) {
+	_ = cap(x)
+}
+
+func _[V ~A]() {
+	_ = V{}
+}
+
+func _[W ~B](a interface{}) {
+	_ = a.(W)["key"]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue68935.go b/src/internal/types/testdata/fixedbugs/issue68935.go
new file mode 100644
index 00000000000000..2e72468f05eb0c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue68935.go
@@ -0,0 +1,26 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type A = struct {
+	F string
+	G int
+}
+
+func Make[T ~A]() T {
+	return T{
+		F: "blah",
+		G: 1234,
+	}
+}
+
+type N struct {
+	F string
+	G int
+}
+
+func _() {
+	_ = Make[N]()
+}
diff --git a/src/internal/weak/pointer_test.go b/src/internal/weak/pointer_test.go
index e143749230f0a5..5a861bb9ca39d7 100644
--- a/src/internal/weak/pointer_test.go
+++ b/src/internal/weak/pointer_test.go
@@ -5,9 +5,12 @@
 package weak_test
 
 import (
+	"context"
 	"internal/weak"
 	"runtime"
+	"sync"
 	"testing"
+	"time"
 )
 
 type T struct {
@@ -128,3 +131,82 @@ func TestPointerFinalizer(t *testing.T) {
 		t.Errorf("weak pointer is non-nil even after finalization: %v", wt)
 	}
 }
+
+// Regression test for issue 69210.
+//
+// Weak-to-strong conversions must shade the new strong pointer, otherwise
+// that might be creating the only strong pointer to a white object which
+// is hidden in a blackened stack.
+//
+// Never fails if correct, fails with some high probability if incorrect.
+func TestIssue69210(t *testing.T) {
+	if testing.Short() {
+		t.Skip("this is a stress test that takes seconds to run on its own")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	defer cancel()
+
+	// What we're trying to do is manufacture the conditions under which this
+	// bug happens. Specifically, we want:
+	//
+	// 1. To create a whole bunch of objects that are only weakly-pointed-to,
+	// 2. To call Strong while the GC is in the mark phase,
+	// 3. The new strong pointer to be missed by the GC,
+	// 4. The following GC cycle to mark a free object.
+	//
+	// Unfortunately, (2) and (3) are hard to control, but we can increase
+	// the likelihood by having several goroutines do (1) at once while
+	// another goroutine constantly keeps us in the GC with runtime.GC.
+	// Like throwing darts at a dart board until they land just right.
+	// We can increase the likelihood of (4) by adding some delay after
+	// creating the strong pointer, but only if it's non-nil. If it's nil,
+	// that means it was already collected in which case there's no chance
+	// of triggering the bug, so we want to retry as fast as possible.
+	// Our heap here is tiny, so the GCs will go by fast.
+	//
+	// As of 2024-09-03, removing the line that shades pointers during
+	// the weak-to-strong conversion causes this test to fail about 50%
+	// of the time.
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			runtime.GC()
+
+			select {
+			case <-ctx.Done():
+				return
+			default:
+			}
+		}
+	}()
+	for range max(runtime.GOMAXPROCS(-1)-1, 1) {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for {
+				for range 5 {
+					bt := new(T)
+					wt := weak.Make(bt)
+					bt = nil
+					time.Sleep(1 * time.Millisecond)
+					bt = wt.Strong()
+					if bt != nil {
+						time.Sleep(4 * time.Millisecond)
+						bt.t = bt
+						bt.a = 12
+					}
+					runtime.KeepAlive(bt)
+				}
+				select {
+				case <-ctx.Done():
+					return
+				default:
+				}
+			}
+		}()
+	}
+	wg.Wait()
+}
diff --git a/src/net/sendfile_unix_alt.go b/src/net/sendfile_unix_alt.go
index 9e46c4e607d4d8..4056856f306175 100644
--- a/src/net/sendfile_unix_alt.go
+++ b/src/net/sendfile_unix_alt.go
@@ -53,6 +53,9 @@ func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
 		if err != nil {
 			return 0, err, false
 		}
+		if fi.Mode()&(fs.ModeSymlink|fs.ModeDevice|fs.ModeCharDevice|fs.ModeIrregular) != 0 {
+			return 0, nil, false
+		}
 
 		remain = fi.Size()
 	}
diff --git a/src/net/sendfile_unix_test.go b/src/net/sendfile_unix_test.go
new file mode 100644
index 00000000000000..79fb23b31010d5
--- /dev/null
+++ b/src/net/sendfile_unix_test.go
@@ -0,0 +1,86 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix
+
+package net
+
+import (
+	"internal/testpty"
+	"io"
+	"os"
+	"sync"
+	"syscall"
+	"testing"
+)
+
+// Issue 70763: test that we don't fail on sendfile from a tty.
+func TestCopyFromTTY(t *testing.T) {
+	pty, ttyName, err := testpty.Open()
+	if err != nil {
+		t.Skipf("skipping test because pty open failed: %v", err)
+	}
+	defer pty.Close()
+
+	// Use syscall.Open so that the tty is blocking.
+	ttyFD, err := syscall.Open(ttyName, syscall.O_RDWR, 0)
+	if err != nil {
+		t.Skipf("skipping test because tty open failed: %v", err)
+	}
+	defer syscall.Close(ttyFD)
+
+	tty := os.NewFile(uintptr(ttyFD), "tty")
+	defer tty.Close()
+
+	ln := newLocalListener(t, "tcp")
+	defer ln.Close()
+
+	ch := make(chan bool)
+
+	const data = "data\n"
+
+	var wg sync.WaitGroup
+	defer wg.Wait()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		conn, err := ln.Accept()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		defer conn.Close()
+
+		buf := make([]byte, len(data))
+		if _, err := io.ReadFull(conn, buf); err != nil {
+			t.Error(err)
+		}
+
+		ch <- true
+	}()
+
+	conn, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		if _, err := pty.Write([]byte(data)); err != nil {
+			t.Error(err)
+		}
+		<-ch
+		if err := pty.Close(); err != nil {
+			t.Error(err)
+		}
+	}()
+
+	lr := io.LimitReader(tty, int64(len(data)))
+	if _, err := io.Copy(conn, lr); err != nil {
+		t.Error(err)
+	}
+}
diff --git a/src/os/copy_test.go b/src/os/copy_test.go
new file mode 100644
index 00000000000000..82346ca4e57e3e
--- /dev/null
+++ b/src/os/copy_test.go
@@ -0,0 +1,154 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os_test
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"math/rand/v2"
+	"net"
+	"os"
+	"runtime"
+	"sync"
+	"testing"
+
+	"golang.org/x/net/nettest"
+)
+
+// Exercise sendfile/splice fast paths with a moderately large file.
+//
+// https://go.dev/issue/70000
+
+func TestLargeCopyViaNetwork(t *testing.T) {
+	const size = 10 * 1024 * 1024
+	dir := t.TempDir()
+
+	src, err := os.Create(dir + "/src")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer src.Close()
+	if _, err := io.CopyN(src, newRandReader(), size); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := src.Seek(0, 0); err != nil {
+		t.Fatal(err)
+	}
+
+	dst, err := os.Create(dir + "/dst")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer dst.Close()
+
+	client, server := createSocketPair(t, "tcp")
+	var wg sync.WaitGroup
+	wg.Add(2)
+	go func() {
+		defer wg.Done()
+		if n, err := io.Copy(dst, server); n != size || err != nil {
+			t.Errorf("copy to destination = %v, %v; want %v, nil", n, err, size)
+		}
+	}()
+	go func() {
+		defer wg.Done()
+		defer client.Close()
+		if n, err := io.Copy(client, src); n != size || err != nil {
+			t.Errorf("copy from source = %v, %v; want %v, nil", n, err, size)
+		}
+	}()
+	wg.Wait()
+
+	if _, err := dst.Seek(0, 0); err != nil {
+		t.Fatal(err)
+	}
+	if err := compareReaders(dst, io.LimitReader(newRandReader(), size)); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func compareReaders(a, b io.Reader) error {
+	bufa := make([]byte, 4096)
+	bufb := make([]byte, 4096)
+	for {
+		na, erra := io.ReadFull(a, bufa)
+		if erra != nil && erra != io.EOF {
+			return erra
+		}
+		nb, errb := io.ReadFull(b, bufb)
+		if errb != nil && errb != io.EOF {
+			return errb
+		}
+		if !bytes.Equal(bufa[:na], bufb[:nb]) {
+			return errors.New("contents mismatch")
+		}
+		if erra == io.EOF && errb == io.EOF {
+			break
+		}
+	}
+	return nil
+}
+
+type randReader struct {
+	rand *rand.Rand
+}
+
+func newRandReader() *randReader {
+	return &randReader{rand.New(rand.NewPCG(0, 0))}
+}
+
+func (r *randReader) Read(p []byte) (int, error) {
+	var v uint64
+	var n int
+	for i := range p {
+		if n == 0 {
+			v = r.rand.Uint64()
+			n = 8
+		}
+		p[i] = byte(v & 0xff)
+		v >>= 8
+		n--
+	}
+	return len(p), nil
+}
+
+func createSocketPair(t *testing.T, proto string) (client, server net.Conn) {
+	t.Helper()
+	if !nettest.TestableNetwork(proto) {
+		t.Skipf("%s does not support %q", runtime.GOOS, proto)
+	}
+
+	ln, err := nettest.NewLocalListener(proto)
+	if err != nil {
+		t.Fatalf("NewLocalListener error: %v", err)
+	}
+	t.Cleanup(func() {
+		if ln != nil {
+			ln.Close()
+		}
+		if client != nil {
+			client.Close()
+		}
+		if server != nil {
+			server.Close()
+		}
+	})
+	ch := make(chan struct{})
+	go func() {
+		var err error
+		server, err = ln.Accept()
+		if err != nil {
+			t.Errorf("Accept new connection error: %v", err)
+		}
+		ch <- struct{}{}
+	}()
+	client, err = net.Dial(proto, ln.Addr().String())
+	<-ch
+	if err != nil {
+		t.Fatalf("Dial new connection error: %v", err)
+	}
+	return client, server
+}
diff --git a/src/os/dir.go b/src/os/dir.go
index 471a29134582b3..04392193aa6b03 100644
--- a/src/os/dir.go
+++ b/src/os/dir.go
@@ -132,15 +132,18 @@ func ReadDir(name string) ([]DirEntry, error) {
 // CopyFS copies the file system fsys into the directory dir,
 // creating dir if necessary.
 //
-// Newly created directories and files have their default modes
-// where any bits from the file in fsys that are not part of the
-// standard read, write, and execute permissions will be zeroed
-// out, and standard read and write permissions are set for owner,
-// group, and others while retaining any existing execute bits from
-// the file in fsys.
+// Files are created with mode 0o666 plus any execute permissions
+// from the source, and directories are created with mode 0o777
+// (before umask).
 //
-// Symbolic links in fsys are not supported, a *PathError with Err set
-// to ErrInvalid is returned on symlink.
+// CopyFS will not overwrite existing files. If a file name in fsys
+// already exists in the destination, CopyFS will return an error
+// such that errors.Is(err, fs.ErrExist) will be true.
+//
+// Symbolic links in fsys are not supported. A *PathError with Err set
+// to ErrInvalid is returned when copying from a symbolic link.
+//
+// Symbolic links in dir are followed.
 //
 // Copying stops at and returns the first error encountered.
 func CopyFS(dir string, fsys fs.FS) error {
@@ -174,7 +177,7 @@ func CopyFS(dir string, fsys fs.FS) error {
 		if err != nil {
 			return err
 		}
-		w, err := OpenFile(newPath, O_CREATE|O_TRUNC|O_WRONLY, 0666|info.Mode()&0777)
+		w, err := OpenFile(newPath, O_CREATE|O_EXCL|O_WRONLY, 0666|info.Mode()&0777)
 		if err != nil {
 			return err
 		}
diff --git a/src/os/example_test.go b/src/os/example_test.go
index 7437a74cd0c66d..c507d46c46303a 100644
--- a/src/os/example_test.go
+++ b/src/os/example_test.go
@@ -61,7 +61,7 @@ func ExampleFileMode() {
 		log.Fatal(err)
 	}
 
-	fmt.Printf("permissions: %#o\n", fi.Mode().Perm()) // 0400, 0777, etc.
+	fmt.Printf("permissions: %#o\n", fi.Mode().Perm()) // 0o400, 0o777, etc.
 	switch mode := fi.Mode(); {
 	case mode.IsRegular():
 		fmt.Println("regular file")
diff --git a/src/os/exec_posix.go b/src/os/exec_posix.go
index cba2e151673aba..ff51247d56b72d 100644
--- a/src/os/exec_posix.go
+++ b/src/os/exec_posix.go
@@ -35,10 +35,11 @@ func startProcess(name string, argv []string, attr *ProcAttr) (p *Process, err e
 		}
 	}
 
+	attrSys, shouldDupPidfd := ensurePidfd(attr.Sys)
 	sysattr := &syscall.ProcAttr{
 		Dir: attr.Dir,
 		Env: attr.Env,
-		Sys: ensurePidfd(attr.Sys),
+		Sys: attrSys,
 	}
 	if sysattr.Env == nil {
 		sysattr.Env, err = execenv.Default(sysattr.Sys)
@@ -63,7 +64,7 @@ func startProcess(name string, argv []string, attr *ProcAttr) (p *Process, err e
 	// For Windows, syscall.StartProcess above already returned a process handle.
 	if runtime.GOOS != "windows" {
 		var ok bool
-		h, ok = getPidfd(sysattr.Sys)
+		h, ok = getPidfd(sysattr.Sys, shouldDupPidfd)
 		if !ok {
 			return newPIDProcess(pid), nil
 		}
diff --git a/src/os/file.go b/src/os/file.go
index c3ee31583e32f6..ad869fc4938d17 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -366,7 +366,7 @@ func Open(name string) (*File, error) {
 }
 
 // Create creates or truncates the named file. If the file already exists,
-// it is truncated. If the file does not exist, it is created with mode 0666
+// it is truncated. If the file does not exist, it is created with mode 0o666
 // (before umask). If successful, methods on the returned File can
 // be used for I/O; the associated file descriptor has mode O_RDWR.
 // If there is an error, it will be of type *PathError.
@@ -602,11 +602,11 @@ func UserHomeDir() (string, error) {
 // On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
 // ModeSticky are used.
 //
-// On Windows, only the 0200 bit (owner writable) of mode is used; it
+// On Windows, only the 0o200 bit (owner writable) of mode is used; it
 // controls whether the file's read-only attribute is set or cleared.
 // The other bits are currently unused. For compatibility with Go 1.12
-// and earlier, use a non-zero mode. Use mode 0400 for a read-only
-// file and 0600 for a readable+writable file.
+// and earlier, use a non-zero mode. Use mode 0o400 for a read-only
+// file and 0o600 for a readable+writable file.
 //
 // On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
 // and ModeTemporary are used.
diff --git a/src/os/os_test.go b/src/os/os_test.go
index 878974384dbcba..f1755dfa9139f8 100644
--- a/src/os/os_test.go
+++ b/src/os/os_test.go
@@ -1376,8 +1376,7 @@ func TestChtimes(t *testing.T) {
 	t.Parallel()
 
 	f := newFile(t)
-
-	f.Write([]byte("hello, world\n"))
+	// This should be an empty file (see #68687, #68663).
 	f.Close()
 
 	testChtimes(t, f.Name())
@@ -1395,12 +1394,9 @@ func TestChtimesOmit(t *testing.T) {
 func testChtimesOmit(t *testing.T, omitAt, omitMt bool) {
 	t.Logf("omit atime: %v, mtime: %v", omitAt, omitMt)
 	file := newFile(t)
-	_, err := file.Write([]byte("hello, world\n"))
-	if err != nil {
-		t.Fatal(err)
-	}
+	// This should be an empty file (see #68687, #68663).
 	name := file.Name()
-	err = file.Close()
+	err := file.Close()
 	if err != nil {
 		t.Error(err)
 	}
@@ -3358,6 +3354,14 @@ func TestCopyFS(t *testing.T) {
 		t.Fatal("comparing two directories:", err)
 	}
 
+	// Test whether CopyFS disallows copying for disk filesystem when there is any
+	// existing file in the destination directory.
+	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
+		t.Errorf("CopyFS should have failed and returned error when there is"+
+			"any existing file in the destination directory (in disk filesystem), "+
+			"got: %v, expected any error that indicates <file exists>", err)
+	}
+
 	// Test with memory filesystem.
 	fsys = fstest.MapFS{
 		"william":    {Data: []byte("Shakespeare\n")},
@@ -3395,6 +3399,14 @@ func TestCopyFS(t *testing.T) {
 	}); err != nil {
 		t.Fatal("comparing two directories:", err)
 	}
+
+	// Test whether CopyFS disallows copying for memory filesystem when there is any
+	// existing file in the destination directory.
+	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
+		t.Errorf("CopyFS should have failed and returned error when there is"+
+			"any existing file in the destination directory (in memory filesystem), "+
+			"got: %v, expected any error that indicates <file exists>", err)
+	}
 }
 
 func TestCopyFSWithSymlinks(t *testing.T) {
diff --git a/src/os/pidfd_linux.go b/src/os/pidfd_linux.go
index 0404c4ff64b72e..0bfef7759cc679 100644
--- a/src/os/pidfd_linux.go
+++ b/src/os/pidfd_linux.go
@@ -8,20 +8,28 @@
 //  v5.3: pidfd_open syscall, clone3 syscall;
 //  v5.4: P_PIDFD idtype support for waitid syscall;
 //  v5.6: pidfd_getfd syscall.
+//
+// N.B. Alternative Linux implementations may not follow this ordering. e.g.,
+// QEMU user mode 7.2 added pidfd_open, but CLONE_PIDFD was not added until
+// 8.0.
 
 package os
 
 import (
 	"errors"
 	"internal/syscall/unix"
+	"runtime"
 	"sync"
 	"syscall"
 	"unsafe"
 )
 
-func ensurePidfd(sysAttr *syscall.SysProcAttr) *syscall.SysProcAttr {
+// ensurePidfd initializes the PidFD field in sysAttr if it is not already set.
+// It returns the original or modified SysProcAttr struct and a flag indicating
+// whether the PidFD should be duplicated before using.
+func ensurePidfd(sysAttr *syscall.SysProcAttr) (*syscall.SysProcAttr, bool) {
 	if !pidfdWorks() {
-		return sysAttr
+		return sysAttr, false
 	}
 
 	var pidfd int
@@ -29,23 +37,33 @@ func ensurePidfd(sysAttr *syscall.SysProcAttr) *syscall.SysProcAttr {
 	if sysAttr == nil {
 		return &syscall.SysProcAttr{
 			PidFD: &pidfd,
-		}
+		}, false
 	}
 	if sysAttr.PidFD == nil {
 		newSys := *sysAttr // copy
 		newSys.PidFD = &pidfd
-		return &newSys
+		return &newSys, false
 	}
 
-	return sysAttr
+	return sysAttr, true
 }
 
-func getPidfd(sysAttr *syscall.SysProcAttr) (uintptr, bool) {
+// getPidfd returns the value of sysAttr.PidFD (or its duplicate if needDup is
+// set) and a flag indicating whether the value can be used.
+func getPidfd(sysAttr *syscall.SysProcAttr, needDup bool) (uintptr, bool) {
 	if !pidfdWorks() {
 		return 0, false
 	}
 
-	return uintptr(*sysAttr.PidFD), true
+	h := *sysAttr.PidFD
+	if needDup {
+		dupH, e := unix.Fcntl(h, syscall.F_DUPFD_CLOEXEC, 0)
+		if e != nil {
+			return 0, false
+		}
+		h = dupH
+	}
+	return uintptr(h), true
 }
 
 func pidfdFind(pid int) (uintptr, error) {
@@ -126,14 +144,21 @@ func pidfdWorks() bool {
 
 var checkPidfdOnce = sync.OnceValue(checkPidfd)
 
-// checkPidfd checks whether all required pidfd-related syscalls work.
-// This consists of pidfd_open and pidfd_send_signal syscalls, and waitid
-// syscall with idtype of P_PIDFD.
+// checkPidfd checks whether all required pidfd-related syscalls work. This
+// consists of pidfd_open and pidfd_send_signal syscalls, waitid syscall with
+// idtype of P_PIDFD, and clone(CLONE_PIDFD).
 //
 // Reasons for non-working pidfd syscalls include an older kernel and an
 // execution environment in which the above system calls are restricted by
 // seccomp or a similar technology.
 func checkPidfd() error {
+	// In Android version < 12, pidfd-related system calls are not allowed
+	// by seccomp and trigger the SIGSYS signal. See issue #69065.
+	if runtime.GOOS == "android" {
+		ignoreSIGSYS()
+		defer restoreSIGSYS()
+	}
+
 	// Get a pidfd of the current process (opening of "/proc/self" won't
 	// work for waitid).
 	fd, err := unix.PidFDOpen(syscall.Getpid(), 0)
@@ -159,5 +184,27 @@ func checkPidfd() error {
 		return NewSyscallError("pidfd_send_signal", err)
 	}
 
+	// Verify that clone(CLONE_PIDFD) works.
+	//
+	// This shouldn't be necessary since pidfd_open was added in Linux 5.3,
+	// after CLONE_PIDFD in Linux 5.2, but some alternative Linux
+	// implementations may not adhere to this ordering.
+	if err := checkClonePidfd(); err != nil {
+		return err
+	}
+
 	return nil
 }
+
+// Provided by syscall.
+//
+//go:linkname checkClonePidfd
+func checkClonePidfd() error
+
+// Provided by runtime.
+//
+//go:linkname ignoreSIGSYS
+func ignoreSIGSYS()
+
+//go:linkname restoreSIGSYS
+func restoreSIGSYS()
diff --git a/src/os/pidfd_linux_test.go b/src/os/pidfd_linux_test.go
index 837593706bae8e..c1f41d02d66c73 100644
--- a/src/os/pidfd_linux_test.go
+++ b/src/os/pidfd_linux_test.go
@@ -6,8 +6,10 @@ package os_test
 
 import (
 	"errors"
+	"internal/syscall/unix"
 	"internal/testenv"
 	"os"
+	"os/exec"
 	"syscall"
 	"testing"
 )
@@ -57,3 +59,93 @@ func TestFindProcessViaPidfd(t *testing.T) {
 		t.Fatalf("Release: got %v, want <nil>", err)
 	}
 }
+
+func TestStartProcessWithPidfd(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	t.Parallel()
+
+	if err := os.CheckPidfdOnce(); err != nil {
+		// Non-pidfd code paths tested in exec_unix_test.go.
+		t.Skipf("skipping: pidfd not available: %v", err)
+	}
+
+	var pidfd int
+	p, err := os.StartProcess(testenv.GoToolPath(t), []string{"go"}, &os.ProcAttr{
+		Sys: &syscall.SysProcAttr{
+			PidFD: &pidfd,
+		},
+	})
+	if err != nil {
+		t.Fatalf("starting test process: %v", err)
+	}
+	defer syscall.Close(pidfd)
+
+	if _, err := p.Wait(); err != nil {
+		t.Fatalf("Wait: got %v, want <nil>", err)
+	}
+
+	// Check the pidfd is still valid
+	err = unix.PidFDSendSignal(uintptr(pidfd), syscall.Signal(0))
+	if !errors.Is(err, syscall.ESRCH) {
+		t.Errorf("SendSignal: got %v, want %v", err, syscall.ESRCH)
+	}
+}
+
+// Issue #69284
+func TestPidfdLeak(t *testing.T) {
+	testenv.MustHaveExec(t)
+	exe, err := os.Executable()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Find the next 10 descriptors.
+	// We need to get more than one descriptor in practice;
+	// the pidfd winds up not being the next descriptor.
+	const count = 10
+	want := make([]int, count)
+	for i := range count {
+		var err error
+		want[i], err = syscall.Open(exe, syscall.O_RDONLY, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Close the descriptors.
+	for _, d := range want {
+		syscall.Close(d)
+	}
+
+	// Start a process 10 times.
+	for range 10 {
+		// For testing purposes this has to be an absolute path.
+		// Otherwise we will fail finding the executable
+		// and won't start a process at all.
+		cmd := exec.Command("/noSuchExecutable")
+		cmd.Run()
+	}
+
+	// Open the next 10 descriptors again.
+	got := make([]int, count)
+	for i := range count {
+		var err error
+		got[i], err = syscall.Open(exe, syscall.O_RDONLY, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Close the descriptors
+	for _, d := range got {
+		syscall.Close(d)
+	}
+
+	t.Logf("got %v", got)
+	t.Logf("want %v", want)
+
+	// Allow some slack for runtime epoll descriptors and the like.
+	if got[count-1] > want[count-1]+5 {
+		t.Errorf("got descriptor %d, want %d", got[count-1], want[count-1])
+	}
+}
diff --git a/src/os/pidfd_other.go b/src/os/pidfd_other.go
index dda4bd0feccae6..ba9cbcb93830c0 100644
--- a/src/os/pidfd_other.go
+++ b/src/os/pidfd_other.go
@@ -8,11 +8,11 @@ package os
 
 import "syscall"
 
-func ensurePidfd(sysAttr *syscall.SysProcAttr) *syscall.SysProcAttr {
-	return sysAttr
+func ensurePidfd(sysAttr *syscall.SysProcAttr) (*syscall.SysProcAttr, bool) {
+	return sysAttr, false
 }
 
-func getPidfd(_ *syscall.SysProcAttr) (uintptr, bool) {
+func getPidfd(_ *syscall.SysProcAttr, _ bool) (uintptr, bool) {
 	return 0, false
 }
 
diff --git a/src/os/readfrom_linux_test.go b/src/os/readfrom_linux_test.go
index 8dcb9cb2172882..45867477dc26b2 100644
--- a/src/os/readfrom_linux_test.go
+++ b/src/os/readfrom_linux_test.go
@@ -14,15 +14,12 @@ import (
 	"net"
 	. "os"
 	"path/filepath"
-	"runtime"
 	"strconv"
 	"strings"
 	"sync"
 	"syscall"
 	"testing"
 	"time"
-
-	"golang.org/x/net/nettest"
 )
 
 func TestCopyFileRange(t *testing.T) {
@@ -784,41 +781,3 @@ func testGetPollFDAndNetwork(t *testing.T, proto string) {
 		t.Fatalf("server Control error: %v", err)
 	}
 }
-
-func createSocketPair(t *testing.T, proto string) (client, server net.Conn) {
-	t.Helper()
-	if !nettest.TestableNetwork(proto) {
-		t.Skipf("%s does not support %q", runtime.GOOS, proto)
-	}
-
-	ln, err := nettest.NewLocalListener(proto)
-	if err != nil {
-		t.Fatalf("NewLocalListener error: %v", err)
-	}
-	t.Cleanup(func() {
-		if ln != nil {
-			ln.Close()
-		}
-		if client != nil {
-			client.Close()
-		}
-		if server != nil {
-			server.Close()
-		}
-	})
-	ch := make(chan struct{})
-	go func() {
-		var err error
-		server, err = ln.Accept()
-		if err != nil {
-			t.Errorf("Accept new connection error: %v", err)
-		}
-		ch <- struct{}{}
-	}()
-	client, err = net.Dial(proto, ln.Addr().String())
-	<-ch
-	if err != nil {
-		t.Fatalf("Dial new connection error: %v", err)
-	}
-	return client, server
-}
diff --git a/src/runtime/cgo/gcc_stack_unix.c b/src/runtime/cgo/gcc_stack_unix.c
index fcb03d0dea7e34..df0049a4f37ab3 100644
--- a/src/runtime/cgo/gcc_stack_unix.c
+++ b/src/runtime/cgo/gcc_stack_unix.c
@@ -31,10 +31,11 @@ x_cgo_getstackbound(uintptr bounds[2])
 	pthread_attr_get_np(pthread_self(), &attr);
 	pthread_attr_getstack(&attr, &addr, &size); // low address
 #else
-	// We don't know how to get the current stacks, so assume they are the
-	// same as the default stack bounds.
-	pthread_attr_getstacksize(&attr, &size);
-	addr = __builtin_frame_address(0) + 4096 - size;
+	// We don't know how to get the current stacks, leave it as
+	// 0 and the caller will use an estimate based on the current
+	// SP.
+	addr = 0;
+	size = 0;
 #endif
 	pthread_attr_destroy(&attr);
 
diff --git a/src/runtime/cgocall.go b/src/runtime/cgocall.go
index b943b1c2d6b4f8..972de4fe03277f 100644
--- a/src/runtime/cgocall.go
+++ b/src/runtime/cgocall.go
@@ -231,34 +231,6 @@ func cgocall(fn, arg unsafe.Pointer) int32 {
 func callbackUpdateSystemStack(mp *m, sp uintptr, signal bool) {
 	g0 := mp.g0
 
-	inBound := sp > g0.stack.lo && sp <= g0.stack.hi
-	if mp.ncgo > 0 && !inBound {
-		// ncgo > 0 indicates that this M was in Go further up the stack
-		// (it called C and is now receiving a callback).
-		//
-		// !inBound indicates that we were called with SP outside the
-		// expected system stack bounds (C changed the stack out from
-		// under us between the cgocall and cgocallback?).
-		//
-		// It is not safe for the C call to change the stack out from
-		// under us, so throw.
-
-		// Note that this case isn't possible for signal == true, as
-		// that is always passing a new M from needm.
-
-		// Stack is bogus, but reset the bounds anyway so we can print.
-		hi := g0.stack.hi
-		lo := g0.stack.lo
-		g0.stack.hi = sp + 1024
-		g0.stack.lo = sp - 32*1024
-		g0.stackguard0 = g0.stack.lo + stackGuard
-		g0.stackguard1 = g0.stackguard0
-
-		print("M ", mp.id, " procid ", mp.procid, " runtime: cgocallback with sp=", hex(sp), " out of bounds [", hex(lo), ", ", hex(hi), "]")
-		print("\n")
-		exit(2)
-	}
-
 	if !mp.isextra {
 		// We allocated the stack for standard Ms. Don't replace the
 		// stack bounds with estimated ones when we already initialized
@@ -266,26 +238,37 @@ func callbackUpdateSystemStack(mp *m, sp uintptr, signal bool) {
 		return
 	}
 
-	// This M does not have Go further up the stack. However, it may have
-	// previously called into Go, initializing the stack bounds. Between
-	// that call returning and now the stack may have changed (perhaps the
-	// C thread is running a coroutine library). We need to update the
-	// stack bounds for this case.
+	inBound := sp > g0.stack.lo && sp <= g0.stack.hi
+	if inBound && mp.g0StackAccurate {
+		// This M has called into Go before and has the stack bounds
+		// initialized. We have the accurate stack bounds, and the SP
+		// is in bounds. We expect it continues to run within the same
+		// bounds.
+		return
+	}
+
+	// We don't have an accurate stack bounds (either it never calls
+	// into Go before, or we couldn't get the accurate bounds), or the
+	// current SP is not within the previous bounds (the stack may have
+	// changed between calls). We need to update the stack bounds.
 	//
 	// N.B. we need to update the stack bounds even if SP appears to
-	// already be in bounds. Our "bounds" may actually be estimated dummy
-	// bounds (below). The actual stack bounds could have shifted but still
-	// have partial overlap with our dummy bounds. If we failed to update
-	// in that case, we could find ourselves seemingly called near the
-	// bottom of the stack bounds, where we quickly run out of space.
+	// already be in bounds, if our bounds are estimated dummy bounds
+	// (below). We may be in a different region within the same actual
+	// stack bounds, but our estimates were not accurate. Or the actual
+	// stack bounds could have shifted but still have partial overlap with
+	// our dummy bounds. If we failed to update in that case, we could find
+	// ourselves seemingly called near the bottom of the stack bounds, where
+	// we quickly run out of space.
 
 	// Set the stack bounds to match the current stack. If we don't
 	// actually know how big the stack is, like we don't know how big any
 	// scheduling stack is, but we assume there's at least 32 kB. If we
 	// can get a more accurate stack bound from pthread, use that, provided
-	// it actually contains SP..
+	// it actually contains SP.
 	g0.stack.hi = sp + 1024
 	g0.stack.lo = sp - 32*1024
+	mp.g0StackAccurate = false
 	if !signal && _cgo_getstackbound != nil {
 		// Don't adjust if called from the signal handler.
 		// We are on the signal stack, not the pthread stack.
@@ -296,12 +279,16 @@ func callbackUpdateSystemStack(mp *m, sp uintptr, signal bool) {
 		asmcgocall(_cgo_getstackbound, unsafe.Pointer(&bounds))
 		// getstackbound is an unsupported no-op on Windows.
 		//
+		// On Unix systems, if the API to get accurate stack bounds is
+		// not available, it returns zeros.
+		//
 		// Don't use these bounds if they don't contain SP. Perhaps we
 		// were called by something not using the standard thread
 		// stack.
 		if bounds[0] != 0 && sp > bounds[0] && sp <= bounds[1] {
 			g0.stack.lo = bounds[0]
 			g0.stack.hi = bounds[1]
+			mp.g0StackAccurate = true
 		}
 	}
 	g0.stackguard0 = g0.stack.lo + stackGuard
@@ -319,6 +306,8 @@ func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
 	}
 
 	sp := gp.m.g0.sched.sp // system sp saved by cgocallback.
+	oldStack := gp.m.g0.stack
+	oldAccurate := gp.m.g0StackAccurate
 	callbackUpdateSystemStack(gp.m, sp, false)
 
 	// The call from C is on gp.m's g0 stack, so we must ensure
@@ -338,9 +327,14 @@ func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
 	// stack. However, since we're returning to an earlier stack frame and
 	// need to pair with the entersyscall() call made by cgocall, we must
 	// save syscall* and let reentersyscall restore them.
+	//
+	// Note: savedsp and savedbp MUST be held in locals as an unsafe.Pointer.
+	// When we call into Go, the stack is free to be moved. If these locals
+	// aren't visible in the stack maps, they won't get updated properly,
+	// and will end up being stale when restored by reentersyscall.
 	savedsp := unsafe.Pointer(gp.syscallsp)
 	savedpc := gp.syscallpc
-	savedbp := gp.syscallbp
+	savedbp := unsafe.Pointer(gp.syscallbp)
 	exitsyscall() // coming out of cgo call
 	gp.m.incgo = false
 	if gp.m.isextra {
@@ -372,9 +366,15 @@ func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
 	osPreemptExtEnter(gp.m)
 
 	// going back to cgo call
-	reentersyscall(savedpc, uintptr(savedsp), savedbp)
+	reentersyscall(savedpc, uintptr(savedsp), uintptr(savedbp))
 
 	gp.m.winsyscall = winsyscall
+
+	// Restore the old g0 stack bounds
+	gp.m.g0.stack = oldStack
+	gp.m.g0.stackguard0 = oldStack.lo + stackGuard
+	gp.m.g0.stackguard1 = gp.m.g0.stackguard0
+	gp.m.g0StackAccurate = oldAccurate
 }
 
 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) {
diff --git a/src/runtime/cgocheck.go b/src/runtime/cgocheck.go
index 3f2c271953db66..44f9eed40208c5 100644
--- a/src/runtime/cgocheck.go
+++ b/src/runtime/cgocheck.go
@@ -30,43 +30,48 @@ func cgoCheckPtrWrite(dst *unsafe.Pointer, src unsafe.Pointer) {
 		// runtime has set itself up.
 		return
 	}
-	if !cgoIsGoPointer(src) {
-		return
-	}
-	if cgoIsGoPointer(unsafe.Pointer(dst)) {
-		return
+	if src != nil {
+		getg().m.p.ptr().ptrWrites++
 	}
+	/*
+		if !cgoIsGoPointer(src) {
+			return
+		}
+		if cgoIsGoPointer(unsafe.Pointer(dst)) {
+			return
+		}
 
-	// If we are running on the system stack then dst might be an
-	// address on the stack, which is OK.
-	gp := getg()
-	if gp == gp.m.g0 || gp == gp.m.gsignal {
-		return
-	}
+		// If we are running on the system stack then dst might be an
+		// address on the stack, which is OK.
+		gp := getg()
+		if gp == gp.m.g0 || gp == gp.m.gsignal {
+			return
+		}
 
-	// Allocating memory can write to various mfixalloc structs
-	// that look like they are non-Go memory.
-	if gp.m.mallocing != 0 {
-		return
-	}
+		// Allocating memory can write to various mfixalloc structs
+		// that look like they are non-Go memory.
+		if gp.m.mallocing != 0 {
+			return
+		}
 
-	// If the object is pinned, it's safe to store it in C memory. The GC
-	// ensures it will not be moved or freed.
-	if isPinned(src) {
-		return
-	}
+		// If the object is pinned, it's safe to store it in C memory. The GC
+		// ensures it will not be moved or freed.
+		if isPinned(src) {
+			return
+		}
 
-	// It's OK if writing to memory allocated by persistentalloc.
-	// Do this check last because it is more expensive and rarely true.
-	// If it is false the expense doesn't matter since we are crashing.
-	if inPersistentAlloc(uintptr(unsafe.Pointer(dst))) {
-		return
-	}
+		// It's OK if writing to memory allocated by persistentalloc.
+		// Do this check last because it is more expensive and rarely true.
+		// If it is false the expense doesn't matter since we are crashing.
+		if inPersistentAlloc(uintptr(unsafe.Pointer(dst))) {
+			return
+		}
 
-	systemstack(func() {
-		println("write of unpinned Go pointer", hex(uintptr(src)), "to non-Go memory", hex(uintptr(unsafe.Pointer(dst))))
-		throw(cgoWriteBarrierFail)
-	})
+		systemstack(func() {
+			println("write of unpinned Go pointer", hex(uintptr(src)), "to non-Go memory", hex(uintptr(unsafe.Pointer(dst))))
+			throw(cgoWriteBarrierFail)
+		})
+	*/
 }
 
 // cgoCheckMemmove is called when moving a block of memory.
@@ -93,13 +98,16 @@ func cgoCheckMemmove2(typ *_type, dst, src unsafe.Pointer, off, size uintptr) {
 	if !typ.Pointers() {
 		return
 	}
-	if !cgoIsGoPointer(src) {
-		return
-	}
-	if cgoIsGoPointer(dst) {
-		return
-	}
-	cgoCheckTypedBlock(typ, src, off, size)
+	countWrittenPointers(typ, 1)
+	/*
+		if !cgoIsGoPointer(src) {
+			return
+		}
+		if cgoIsGoPointer(dst) {
+			return
+		}
+		cgoCheckTypedBlock(typ, src, off, size)
+	*/
 }
 
 // cgoCheckSliceCopy is called when copying n elements of a slice.
@@ -114,17 +122,20 @@ func cgoCheckSliceCopy(typ *_type, dst, src unsafe.Pointer, n int) {
 	if !typ.Pointers() {
 		return
 	}
-	if !cgoIsGoPointer(src) {
-		return
-	}
-	if cgoIsGoPointer(dst) {
-		return
-	}
-	p := src
-	for i := 0; i < n; i++ {
-		cgoCheckTypedBlock(typ, p, 0, typ.Size_)
-		p = add(p, typ.Size_)
-	}
+	countWrittenPointers(typ, n)
+	/*
+		if !cgoIsGoPointer(src) {
+			return
+		}
+		if cgoIsGoPointer(dst) {
+			return
+		}
+		p := src
+		for i := 0; i < n; i++ {
+			cgoCheckTypedBlock(typ, p, 0, typ.Size_)
+			p = add(p, typ.Size_)
+		}
+	*/
 }
 
 // cgoCheckTypedBlock checks the block of memory at src, for up to size bytes,
@@ -190,6 +201,21 @@ func cgoCheckTypedBlock(typ *_type, src unsafe.Pointer, off, size uintptr) {
 	}
 }
 
+//go:nosplit
+//go:nowritebarrier
+func countWrittenPointers(typ *_type, n int) {
+	ptrs := uint64(0)
+	for i := uintptr(0); i < typ.PtrBytes; i += goarch.PtrSize * ptrBits {
+		b := uint64(readUintptr(addb(typ.GCData, i/ptrBits)))
+		for j := range 64 {
+			if b&(uint64(1)<<j) != 0 {
+				ptrs++
+			}
+		}
+	}
+	getg().m.p.ptr().ptrWrites += ptrs * uint64(n)
+}
+
 // cgoCheckBits checks the block of memory at src, for up to size
 // bytes, and throws if it finds an unpinned Go pointer. The gcbits mark each
 // pointer value. The src pointer is off bytes into the gcbits.
diff --git a/src/runtime/coro.go b/src/runtime/coro.go
index 30ada455e4985e..d93817f92f1caa 100644
--- a/src/runtime/coro.go
+++ b/src/runtime/coro.go
@@ -208,6 +208,18 @@ func coroswitch_m(gp *g) {
 	// directly if possible.
 	setGNoWB(&mp.curg, gnext)
 	setMNoWB(&gnext.m, mp)
+
+	// Synchronize with any out-standing goroutine profile. We're about to start
+	// executing, and an invariant of the profiler is that we tryRecordGoroutineProfile
+	// whenever a goroutine is about to start running.
+	//
+	// N.B. We must do this before transitioning to _Grunning but after installing gnext
+	// in curg, so that we have a valid curg for allocation (tryRecordGoroutineProfile
+	// may allocate).
+	if goroutineProfile.active {
+		tryRecordGoroutineProfile(gnext, nil, osyield)
+	}
+
 	if !gnext.atomicstatus.CompareAndSwap(_Gwaiting, _Grunning) {
 		// The CAS failed: use casgstatus, which will take care of
 		// coordinating with the garbage collector about the state change.
diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index d55da1028dbb1c..4502fa72a10371 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -1886,3 +1886,30 @@ func (m *TraceMap) PutString(s string) (uint64, bool) {
 func (m *TraceMap) Reset() {
 	m.traceMap.reset()
 }
+
+func SetSpinInGCMarkDone(spin bool) {
+	gcDebugMarkDone.spinAfterRaggedBarrier.Store(spin)
+}
+
+func GCMarkDoneRestarted() bool {
+	// Only read this outside of the GC. If we're running during a GC, just report false.
+	mp := acquirem()
+	if gcphase != _GCoff {
+		releasem(mp)
+		return false
+	}
+	restarted := gcDebugMarkDone.restartedDueTo27993
+	releasem(mp)
+	return restarted
+}
+
+func GCMarkDoneResetRestartFlag() {
+	mp := acquirem()
+	for gcphase != _GCoff {
+		releasem(mp)
+		Gosched()
+		mp = acquirem()
+	}
+	gcDebugMarkDone.restartedDueTo27993 = false
+	releasem(mp)
+}
diff --git a/src/runtime/extern.go b/src/runtime/extern.go
index 2019be4ddec4f3..fce67adb7d80d3 100644
--- a/src/runtime/extern.go
+++ b/src/runtime/extern.go
@@ -89,6 +89,10 @@ It is a comma-separated list of name=val pairs setting these named variables:
 	making every garbage collection a stop-the-world event. Setting gcstoptheworld=2
 	also disables concurrent sweeping after the garbage collection finishes.
 
+	gcnoassist: setting gcnoassist=1 disables garbage collection assist, minimizing
+	garbage collection overhead for user goroutines at the expense of a higher risk
+	of out-of-memory failures with high allocation rates.
+
 	gctrace: setting gctrace=1 causes the garbage collector to emit a single line to standard
 	error at each collection, summarizing the amount of memory collected and the
 	length of the pause. The format of this line is subject to change. Included in
diff --git a/src/runtime/gc_test.go b/src/runtime/gc_test.go
index 908f6322466b17..4b92b200674386 100644
--- a/src/runtime/gc_test.go
+++ b/src/runtime/gc_test.go
@@ -6,6 +6,8 @@ package runtime_test
 
 import (
 	"fmt"
+	"internal/testenv"
+	"internal/weak"
 	"math/bits"
 	"math/rand"
 	"os"
@@ -787,3 +789,78 @@ func TestMemoryLimitNoGCPercent(t *testing.T) {
 func TestMyGenericFunc(t *testing.T) {
 	runtime.MyGenericFunc[int]()
 }
+
+func TestWeakToStrongMarkTermination(t *testing.T) {
+	testenv.MustHaveParallelism(t)
+
+	type T struct {
+		a *int
+		b int
+	}
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+	w := make([]weak.Pointer[T], 2048)
+
+	// Make sure there's no out-standing GC from a previous test.
+	runtime.GC()
+
+	// Create many objects with a weak pointers to them.
+	for i := range w {
+		x := new(T)
+		x.a = new(int)
+		w[i] = weak.Make(x)
+	}
+
+	// Reset the restart flag.
+	runtime.GCMarkDoneResetRestartFlag()
+
+	// Prevent mark termination from completing.
+	runtime.SetSpinInGCMarkDone(true)
+
+	// Start a GC, and wait a little bit to get something spinning in mark termination.
+	// Simultaneously, fire off another goroutine to disable spinning. If everything's
+	// working correctly, then weak.Strong will block, so we need to make sure something
+	// prevents the GC from continuing to spin.
+	done := make(chan struct{})
+	go func() {
+		runtime.GC()
+		done <- struct{}{}
+	}()
+	go func() {
+		time.Sleep(100 * time.Millisecond)
+
+		// Let mark termination continue.
+		runtime.SetSpinInGCMarkDone(false)
+	}()
+	time.Sleep(10 * time.Millisecond)
+
+	// Perform many weak->strong conversions in the critical window.
+	var wg sync.WaitGroup
+	for _, wp := range w {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			wp.Strong()
+		}()
+	}
+
+	// Make sure the GC completes.
+	<-done
+
+	// Make sure all the weak->strong conversions finish.
+	wg.Wait()
+
+	// The bug is triggered if there's still mark work after gcMarkDone stops the world.
+	//
+	// This can manifest in one of two ways today:
+	// - An exceedingly rare crash in mark termination.
+	// - gcMarkDone restarts, as if issue #27993 is at play.
+	//
+	// Check for the latter. This is a fairly controlled environment, so #27993 is very
+	// unlikely to happen (it's already rare to begin with) but we'll always _appear_ to
+	// trigger the same bug if weak->strong conversions aren't properly coordinated with
+	// mark termination.
+	if runtime.GCMarkDoneRestarted() {
+		t.Errorf("gcMarkDone restarted")
+	}
+}
diff --git a/src/runtime/internal/sys/intrinsics.go b/src/runtime/internal/sys/intrinsics.go
index e6a3758447f95e..196a93df7242e5 100644
--- a/src/runtime/internal/sys/intrinsics.go
+++ b/src/runtime/internal/sys/intrinsics.go
@@ -119,6 +119,10 @@ const m1 = 0x3333333333333333 // 00110011 ...
 const m2 = 0x0f0f0f0f0f0f0f0f // 00001111 ...
 
 // OnesCount64 returns the number of one bits ("population count") in x.
+//
+// nosplit because this is used in the cgocheck2 code for memmoves.
+//
+//go:nosplit
 func OnesCount64(x uint64) int {
 	// Implementation: Parallel summing of adjacent bits.
 	// See "Hacker's Delight", Chap. 5: Counting Bits.
diff --git a/src/runtime/lock_futex.go b/src/runtime/lock_futex.go
index 58690e45e4d5a8..4aafc3e44d3496 100644
--- a/src/runtime/lock_futex.go
+++ b/src/runtime/lock_futex.go
@@ -48,6 +48,7 @@ func mutexContended(l *mutex) bool {
 	return atomic.Load(key32(&l.key)) > mutex_locked
 }
 
+//go:linkname lock
 func lock(l *mutex) {
 	lockWithRank(l, getLockRank(l))
 }
@@ -117,6 +118,7 @@ func lock2(l *mutex) {
 	}
 }
 
+//go:linkname unlock
 func unlock(l *mutex) {
 	unlockWithRank(l)
 }
diff --git a/src/runtime/lock_js.go b/src/runtime/lock_js.go
index b6ee5ec7afe269..5ca1e3d5611abb 100644
--- a/src/runtime/lock_js.go
+++ b/src/runtime/lock_js.go
@@ -27,6 +27,7 @@ func mutexContended(l *mutex) bool {
 	return false
 }
 
+//go:linkname lock
 func lock(l *mutex) {
 	lockWithRank(l, getLockRank(l))
 }
@@ -45,6 +46,7 @@ func lock2(l *mutex) {
 	l.key = mutex_locked
 }
 
+//go:linkname unlock
 func unlock(l *mutex) {
 	unlockWithRank(l)
 }
diff --git a/src/runtime/lock_sema.go b/src/runtime/lock_sema.go
index 32d2235ad3ab90..20a0243655465f 100644
--- a/src/runtime/lock_sema.go
+++ b/src/runtime/lock_sema.go
@@ -35,6 +35,7 @@ func mutexContended(l *mutex) bool {
 	return atomic.Loaduintptr(&l.key) > locked
 }
 
+//go:linkname lock
 func lock(l *mutex) {
 	lockWithRank(l, getLockRank(l))
 }
@@ -99,6 +100,7 @@ Loop:
 	}
 }
 
+//go:linkname unlock
 func unlock(l *mutex) {
 	unlockWithRank(l)
 }
diff --git a/src/runtime/lock_wasip1.go b/src/runtime/lock_wasip1.go
index acfc62acb48e90..2c5bd3c5907916 100644
--- a/src/runtime/lock_wasip1.go
+++ b/src/runtime/lock_wasip1.go
@@ -23,6 +23,7 @@ func mutexContended(l *mutex) bool {
 	return false
 }
 
+//go:linkname lock
 func lock(l *mutex) {
 	lockWithRank(l, getLockRank(l))
 }
@@ -41,6 +42,7 @@ func lock2(l *mutex) {
 	l.key = mutex_locked
 }
 
+//go:linkname unlock
 func unlock(l *mutex) {
 	unlockWithRank(l)
 }
diff --git a/src/runtime/lockrank.go b/src/runtime/lockrank.go
index 432ace728b8269..373838332f564a 100644
--- a/src/runtime/lockrank.go
+++ b/src/runtime/lockrank.go
@@ -17,6 +17,7 @@ const (
 	lockRankDefer
 	lockRankSweepWaiters
 	lockRankAssistQueue
+	lockRankStrongFromWeakQueue
 	lockRankSweep
 	lockRankTestR
 	lockRankTestW
@@ -84,64 +85,65 @@ const lockRankLeafRank lockRank = 1000
 
 // lockNames gives the names associated with each of the above ranks.
 var lockNames = []string{
-	lockRankSysmon:          "sysmon",
-	lockRankScavenge:        "scavenge",
-	lockRankForcegc:         "forcegc",
-	lockRankDefer:           "defer",
-	lockRankSweepWaiters:    "sweepWaiters",
-	lockRankAssistQueue:     "assistQueue",
-	lockRankSweep:           "sweep",
-	lockRankTestR:           "testR",
-	lockRankTestW:           "testW",
-	lockRankTimerSend:       "timerSend",
-	lockRankAllocmW:         "allocmW",
-	lockRankExecW:           "execW",
-	lockRankCpuprof:         "cpuprof",
-	lockRankPollCache:       "pollCache",
-	lockRankPollDesc:        "pollDesc",
-	lockRankWakeableSleep:   "wakeableSleep",
-	lockRankHchan:           "hchan",
-	lockRankAllocmR:         "allocmR",
-	lockRankExecR:           "execR",
-	lockRankSched:           "sched",
-	lockRankAllg:            "allg",
-	lockRankAllp:            "allp",
-	lockRankNotifyList:      "notifyList",
-	lockRankSudog:           "sudog",
-	lockRankTimers:          "timers",
-	lockRankTimer:           "timer",
-	lockRankNetpollInit:     "netpollInit",
-	lockRankRoot:            "root",
-	lockRankItab:            "itab",
-	lockRankReflectOffs:     "reflectOffs",
-	lockRankUserArenaState:  "userArenaState",
-	lockRankTraceBuf:        "traceBuf",
-	lockRankTraceStrings:    "traceStrings",
-	lockRankFin:             "fin",
-	lockRankSpanSetSpine:    "spanSetSpine",
-	lockRankMspanSpecial:    "mspanSpecial",
-	lockRankTraceTypeTab:    "traceTypeTab",
-	lockRankGcBitsArenas:    "gcBitsArenas",
-	lockRankProfInsert:      "profInsert",
-	lockRankProfBlock:       "profBlock",
-	lockRankProfMemActive:   "profMemActive",
-	lockRankProfMemFuture:   "profMemFuture",
-	lockRankGscan:           "gscan",
-	lockRankStackpool:       "stackpool",
-	lockRankStackLarge:      "stackLarge",
-	lockRankHchanLeaf:       "hchanLeaf",
-	lockRankWbufSpans:       "wbufSpans",
-	lockRankMheap:           "mheap",
-	lockRankMheapSpecial:    "mheapSpecial",
-	lockRankGlobalAlloc:     "globalAlloc",
-	lockRankTrace:           "trace",
-	lockRankTraceStackTab:   "traceStackTab",
-	lockRankPanic:           "panic",
-	lockRankDeadlock:        "deadlock",
-	lockRankRaceFini:        "raceFini",
-	lockRankAllocmRInternal: "allocmRInternal",
-	lockRankExecRInternal:   "execRInternal",
-	lockRankTestRInternal:   "testRInternal",
+	lockRankSysmon:              "sysmon",
+	lockRankScavenge:            "scavenge",
+	lockRankForcegc:             "forcegc",
+	lockRankDefer:               "defer",
+	lockRankSweepWaiters:        "sweepWaiters",
+	lockRankAssistQueue:         "assistQueue",
+	lockRankStrongFromWeakQueue: "strongFromWeakQueue",
+	lockRankSweep:               "sweep",
+	lockRankTestR:               "testR",
+	lockRankTestW:               "testW",
+	lockRankTimerSend:           "timerSend",
+	lockRankAllocmW:             "allocmW",
+	lockRankExecW:               "execW",
+	lockRankCpuprof:             "cpuprof",
+	lockRankPollCache:           "pollCache",
+	lockRankPollDesc:            "pollDesc",
+	lockRankWakeableSleep:       "wakeableSleep",
+	lockRankHchan:               "hchan",
+	lockRankAllocmR:             "allocmR",
+	lockRankExecR:               "execR",
+	lockRankSched:               "sched",
+	lockRankAllg:                "allg",
+	lockRankAllp:                "allp",
+	lockRankNotifyList:          "notifyList",
+	lockRankSudog:               "sudog",
+	lockRankTimers:              "timers",
+	lockRankTimer:               "timer",
+	lockRankNetpollInit:         "netpollInit",
+	lockRankRoot:                "root",
+	lockRankItab:                "itab",
+	lockRankReflectOffs:         "reflectOffs",
+	lockRankUserArenaState:      "userArenaState",
+	lockRankTraceBuf:            "traceBuf",
+	lockRankTraceStrings:        "traceStrings",
+	lockRankFin:                 "fin",
+	lockRankSpanSetSpine:        "spanSetSpine",
+	lockRankMspanSpecial:        "mspanSpecial",
+	lockRankTraceTypeTab:        "traceTypeTab",
+	lockRankGcBitsArenas:        "gcBitsArenas",
+	lockRankProfInsert:          "profInsert",
+	lockRankProfBlock:           "profBlock",
+	lockRankProfMemActive:       "profMemActive",
+	lockRankProfMemFuture:       "profMemFuture",
+	lockRankGscan:               "gscan",
+	lockRankStackpool:           "stackpool",
+	lockRankStackLarge:          "stackLarge",
+	lockRankHchanLeaf:           "hchanLeaf",
+	lockRankWbufSpans:           "wbufSpans",
+	lockRankMheap:               "mheap",
+	lockRankMheapSpecial:        "mheapSpecial",
+	lockRankGlobalAlloc:         "globalAlloc",
+	lockRankTrace:               "trace",
+	lockRankTraceStackTab:       "traceStackTab",
+	lockRankPanic:               "panic",
+	lockRankDeadlock:            "deadlock",
+	lockRankRaceFini:            "raceFini",
+	lockRankAllocmRInternal:     "allocmRInternal",
+	lockRankExecRInternal:       "execRInternal",
+	lockRankTestRInternal:       "testRInternal",
 }
 
 func (rank lockRank) String() string {
@@ -163,62 +165,63 @@ func (rank lockRank) String() string {
 //
 // Lock ranks that allow self-cycles list themselves.
 var lockPartialOrder [][]lockRank = [][]lockRank{
-	lockRankSysmon:          {},
-	lockRankScavenge:        {lockRankSysmon},
-	lockRankForcegc:         {lockRankSysmon},
-	lockRankDefer:           {},
-	lockRankSweepWaiters:    {},
-	lockRankAssistQueue:     {},
-	lockRankSweep:           {},
-	lockRankTestR:           {},
-	lockRankTestW:           {},
-	lockRankTimerSend:       {},
-	lockRankAllocmW:         {},
-	lockRankExecW:           {},
-	lockRankCpuprof:         {},
-	lockRankPollCache:       {},
-	lockRankPollDesc:        {},
-	lockRankWakeableSleep:   {},
-	lockRankHchan:           {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankWakeableSleep, lockRankHchan},
-	lockRankAllocmR:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan},
-	lockRankExecR:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan},
-	lockRankSched:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR},
-	lockRankAllg:            {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched},
-	lockRankAllp:            {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched},
-	lockRankNotifyList:      {},
-	lockRankSudog:           {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankWakeableSleep, lockRankHchan, lockRankNotifyList},
-	lockRankTimers:          {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankTimers},
-	lockRankTimer:           {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankTimers},
-	lockRankNetpollInit:     {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankTimers, lockRankTimer},
-	lockRankRoot:            {},
-	lockRankItab:            {},
-	lockRankReflectOffs:     {lockRankItab},
-	lockRankUserArenaState:  {},
-	lockRankTraceBuf:        {lockRankSysmon, lockRankScavenge},
-	lockRankTraceStrings:    {lockRankSysmon, lockRankScavenge, lockRankTraceBuf},
-	lockRankFin:             {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankSpanSetSpine:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankMspanSpecial:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankTraceTypeTab:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankGcBitsArenas:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial},
-	lockRankProfInsert:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfBlock:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfMemActive:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfMemFuture:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankProfMemActive},
-	lockRankGscan:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture},
-	lockRankStackpool:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
-	lockRankStackLarge:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
-	lockRankHchanLeaf:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankHchanLeaf},
-	lockRankWbufSpans:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
-	lockRankMheap:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans},
-	lockRankMheapSpecial:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
-	lockRankGlobalAlloc:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankMheapSpecial},
-	lockRankTrace:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
-	lockRankTraceStackTab:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankTrace},
-	lockRankPanic:           {},
-	lockRankDeadlock:        {lockRankPanic, lockRankDeadlock},
-	lockRankRaceFini:        {lockRankPanic},
-	lockRankAllocmRInternal: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankAllocmW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR},
-	lockRankExecRInternal:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankExecR},
-	lockRankTestRInternal:   {lockRankTestR, lockRankTestW},
+	lockRankSysmon:              {},
+	lockRankScavenge:            {lockRankSysmon},
+	lockRankForcegc:             {lockRankSysmon},
+	lockRankDefer:               {},
+	lockRankSweepWaiters:        {},
+	lockRankAssistQueue:         {},
+	lockRankStrongFromWeakQueue: {},
+	lockRankSweep:               {},
+	lockRankTestR:               {},
+	lockRankTestW:               {},
+	lockRankTimerSend:           {},
+	lockRankAllocmW:             {},
+	lockRankExecW:               {},
+	lockRankCpuprof:             {},
+	lockRankPollCache:           {},
+	lockRankPollDesc:            {},
+	lockRankWakeableSleep:       {},
+	lockRankHchan:               {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankWakeableSleep, lockRankHchan},
+	lockRankAllocmR:             {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan},
+	lockRankExecR:               {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan},
+	lockRankSched:               {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR},
+	lockRankAllg:                {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched},
+	lockRankAllp:                {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched},
+	lockRankNotifyList:          {},
+	lockRankSudog:               {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankWakeableSleep, lockRankHchan, lockRankNotifyList},
+	lockRankTimers:              {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankTimers},
+	lockRankTimer:               {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankTimers},
+	lockRankNetpollInit:         {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankTimers, lockRankTimer},
+	lockRankRoot:                {},
+	lockRankItab:                {},
+	lockRankReflectOffs:         {lockRankItab},
+	lockRankUserArenaState:      {},
+	lockRankTraceBuf:            {lockRankSysmon, lockRankScavenge},
+	lockRankTraceStrings:        {lockRankSysmon, lockRankScavenge, lockRankTraceBuf},
+	lockRankFin:                 {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankSpanSetSpine:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankMspanSpecial:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankTraceTypeTab:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankGcBitsArenas:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial},
+	lockRankProfInsert:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfBlock:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfMemActive:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfMemFuture:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankProfMemActive},
+	lockRankGscan:               {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture},
+	lockRankStackpool:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
+	lockRankStackLarge:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
+	lockRankHchanLeaf:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankHchanLeaf},
+	lockRankWbufSpans:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
+	lockRankMheap:               {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans},
+	lockRankMheapSpecial:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
+	lockRankGlobalAlloc:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankMheapSpecial},
+	lockRankTrace:               {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
+	lockRankTraceStackTab:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollCache, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankNotifyList, lockRankSudog, lockRankTimers, lockRankTimer, lockRankNetpollInit, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankTrace},
+	lockRankPanic:               {},
+	lockRankDeadlock:            {lockRankPanic, lockRankDeadlock},
+	lockRankRaceFini:            {lockRankPanic},
+	lockRankAllocmRInternal:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankAllocmW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankAllocmR},
+	lockRankExecRInternal:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankExecR},
+	lockRankTestRInternal:       {lockRankTestR, lockRankTestW},
 }
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index b92a213245d4f7..112fd876d0e199 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1332,7 +1332,7 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
 // Returns the G for which the assist credit was accounted.
 func deductAssistCredit(size uintptr) *g {
 	var assistG *g
-	if gcBlackenEnabled != 0 {
+	if debug.gcnoassist == 0 && gcBlackenEnabled != 0 {
 		// Charge the current user G for this allocation.
 		assistG = getg()
 		if assistG.m.curg != nil {
diff --git a/src/runtime/map.go b/src/runtime/map.go
index 112084f5a74091..52d56fb57a4dc6 100644
--- a/src/runtime/map.go
+++ b/src/runtime/map.go
@@ -1209,6 +1209,11 @@ func (h *hmap) sameSizeGrow() bool {
 	return h.flags&sameSizeGrow != 0
 }
 
+//go:linkname sameSizeGrowForIssue69110Test
+func sameSizeGrowForIssue69110Test(h *hmap) bool {
+	return h.sameSizeGrow()
+}
+
 // noldbuckets calculates the number of buckets prior to the current map growth.
 func (h *hmap) noldbuckets() uintptr {
 	oldB := h.B
@@ -1668,7 +1673,16 @@ func moveToBmap(t *maptype, h *hmap, dst *bmap, pos int, src *bmap) (*bmap, int)
 }
 
 func mapclone2(t *maptype, src *hmap) *hmap {
-	dst := makemap(t, src.count, nil)
+	hint := src.count
+	if overLoadFactor(hint, src.B) {
+		// Note: in rare cases (e.g. during a same-sized grow) the map
+		// can be overloaded. Make sure we don't allocate a destination
+		// bucket array larger than the source bucket array.
+		// This will cause the cloned map to be overloaded also,
+		// but that's better than crashing. See issue 69110.
+		hint = int(loadFactorNum * (bucketShift(src.B) / loadFactorDen))
+	}
+	dst := makemap(t, hint, nil)
 	dst.hash0 = src.hash0
 	dst.nevacuate = 0
 	// flags do not need to be copied here, just like a new map has no flags.
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 2654c696582211..1347bd1622c685 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -130,6 +130,7 @@ package runtime
 
 import (
 	"internal/cpu"
+	"internal/goexperiment"
 	"internal/runtime/atomic"
 	"unsafe"
 )
@@ -190,6 +191,7 @@ func gcinit() {
 	work.markDoneSema = 1
 	lockInit(&work.sweepWaiters.lock, lockRankSweepWaiters)
 	lockInit(&work.assistQueue.lock, lockRankAssistQueue)
+	lockInit(&work.strongFromWeak.lock, lockRankStrongFromWeakQueue)
 	lockInit(&work.wbufSpans.lock, lockRankWbufSpans)
 }
 
@@ -418,6 +420,26 @@ type workType struct {
 		list gList
 	}
 
+	// strongFromWeak controls how the GC interacts with weak->strong
+	// pointer conversions.
+	strongFromWeak struct {
+		// block is a flag set during mark termination that prevents
+		// new weak->strong conversions from executing by blocking the
+		// goroutine and enqueuing it onto q.
+		//
+		// Mutated only by one goroutine at a time in gcMarkDone,
+		// with globally-synchronizing events like forEachP and
+		// stopTheWorld.
+		block bool
+
+		// q is a queue of goroutines that attempted to perform a
+		// weak->strong conversion during mark termination.
+		//
+		// Protected by lock.
+		lock mutex
+		q    gQueue
+	}
+
 	// cycles is the number of completed GC cycles, where a GC
 	// cycle is sweep termination, mark, mark termination, and
 	// sweep. This differs from memstats.numgc, which is
@@ -800,6 +822,19 @@ func gcStart(trigger gcTrigger) {
 // This is protected by markDoneSema.
 var gcMarkDoneFlushed uint32
 
+// gcDebugMarkDone contains fields used to debug/test mark termination.
+var gcDebugMarkDone struct {
+	// spinAfterRaggedBarrier forces gcMarkDone to spin after it executes
+	// the ragged barrier.
+	spinAfterRaggedBarrier atomic.Bool
+
+	// restartedDueTo27993 indicates that we restarted mark termination
+	// due to the bug described in issue #27993.
+	//
+	// Protected by worldsema.
+	restartedDueTo27993 bool
+}
+
 // gcMarkDone transitions the GC from mark to mark termination if all
 // reachable objects have been marked (that is, there are no grey
 // objects and can be no more in the future). Otherwise, it flushes
@@ -842,6 +877,10 @@ top:
 	// stop the world later, so acquire worldsema now.
 	semacquire(&worldsema)
 
+	// Prevent weak->strong conversions from generating additional
+	// GC work. forEachP will guarantee that it is observed globally.
+	work.strongFromWeak.block = true
+
 	// Flush all local buffers and collect flushedWork flags.
 	gcMarkDoneFlushed = 0
 	forEachP(waitReasonGCMarkTermination, func(pp *p) {
@@ -872,6 +911,10 @@ top:
 		goto top
 	}
 
+	// For debugging/testing.
+	for gcDebugMarkDone.spinAfterRaggedBarrier.Load() {
+	}
+
 	// There was no global work, no local work, and no Ps
 	// communicated work since we took markDoneSema. Therefore
 	// there are no grey objects and no more objects can be
@@ -910,6 +953,8 @@ top:
 		}
 	})
 	if restart {
+		gcDebugMarkDone.restartedDueTo27993 = true
+
 		getg().m.preemptoff = ""
 		systemstack(func() {
 			// Accumulate the time we were stopped before we had to start again.
@@ -936,6 +981,11 @@ top:
 	// start the world again.
 	gcWakeAllAssists()
 
+	// Wake all blocked weak->strong conversions. These will run
+	// when we start the world again.
+	work.strongFromWeak.block = false
+	gcWakeAllStrongFromWeak()
+
 	// Likewise, release the transition lock. Blocked
 	// workers and assists will run when we start the
 	// world again.
@@ -1113,6 +1163,14 @@ func gcMarkTermination(stw worldStop) {
 		throw("non-concurrent sweep failed to drain all sweep queues")
 	}
 
+	// Accumulate pointer writes before restarting the world.
+	ptrWrites := uint64(0)
+	if goexperiment.CgoCheck2 {
+		for _, pp := range allp {
+			ptrWrites += pp.ptrWrites
+		}
+	}
+
 	systemstack(func() {
 		// The memstats updated above must be updated with the world
 		// stopped to ensure consistency of some values, such as
@@ -1215,6 +1273,19 @@ func gcMarkTermination(stw worldStop) {
 		if work.userForced {
 			print(" (forced)")
 		}
+		if goexperiment.CgoCheck2 {
+			var stats heapStatsDelta
+			memstats.heapStats.read(&stats)
+			allocs := stats.tinyAllocCount + stats.largeAllocCount
+			allocBytes := stats.largeAlloc
+			for i, c := range stats.smallAllocCount {
+				allocs += c
+				allocBytes += c * uint64(class_to_size[i])
+			}
+			print(" ", ptrWrites, "w")
+			print(" ", allocs, "o")
+			print(" ", allocBytes, "b")
+		}
 		print("\n")
 		printunlock()
 	}
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 35fd08af50c3c1..bfca2d105b7426 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -2049,8 +2049,19 @@ func internal_weak_runtime_registerWeakPointer(p unsafe.Pointer) unsafe.Pointer
 func internal_weak_runtime_makeStrongFromWeak(u unsafe.Pointer) unsafe.Pointer {
 	handle := (*atomic.Uintptr)(u)
 
-	// Prevent preemption. We want to make sure that another GC cycle can't start.
+	// Prevent preemption. We want to make sure that another GC cycle can't start
+	// and that work.strongFromWeak.block can't change out from under us.
 	mp := acquirem()
+
+	// Yield to the GC if necessary.
+	if work.strongFromWeak.block {
+		releasem(mp)
+
+		// Try to park and wait for mark termination.
+		// N.B. gcParkStrongFromWeak calls acquirem before returning.
+		mp = gcParkStrongFromWeak()
+	}
+
 	p := handle.Load()
 	if p == 0 {
 		releasem(mp)
@@ -2073,14 +2084,67 @@ func internal_weak_runtime_makeStrongFromWeak(u unsafe.Pointer) unsafe.Pointer {
 	// Even if we just swept some random span that doesn't contain this object, because
 	// this object is long dead and its memory has since been reused, we'll just observe nil.
 	ptr := unsafe.Pointer(handle.Load())
+
+	// This is responsible for maintaining the same GC-related
+	// invariants as the Yuasa part of the write barrier. During
+	// the mark phase, it's possible that we just created the only
+	// valid pointer to the object pointed to by ptr. If it's only
+	// ever referenced from our stack, and our stack is blackened
+	// already, we could fail to mark it. So, mark it now.
+	if gcphase != _GCoff {
+		shade(uintptr(ptr))
+	}
 	releasem(mp)
+
+	// Explicitly keep ptr alive. This seems unnecessary since we return ptr,
+	// but let's be explicit since it's important we keep ptr alive across the
+	// call to shade.
+	KeepAlive(ptr)
 	return ptr
 }
 
+// gcParkStrongFromWeak puts the current goroutine on the weak->strong queue and parks.
+func gcParkStrongFromWeak() *m {
+	// Prevent preemption as we check strongFromWeak, so it can't change out from under us.
+	mp := acquirem()
+
+	for work.strongFromWeak.block {
+		lock(&work.strongFromWeak.lock)
+		releasem(mp) // N.B. Holding the lock prevents preemption.
+
+		// Queue ourselves up.
+		work.strongFromWeak.q.pushBack(getg())
+
+		// Park.
+		goparkunlock(&work.strongFromWeak.lock, waitReasonGCWeakToStrongWait, traceBlockGCWeakToStrongWait, 2)
+
+		// Re-acquire the current M since we're going to check the condition again.
+		mp = acquirem()
+
+		// Re-check condition. We may have awoken in the next GC's mark termination phase.
+	}
+	return mp
+}
+
+// gcWakeAllStrongFromWeak wakes all currently blocked weak->strong
+// conversions. This is used at the end of a GC cycle.
+//
+// work.strongFromWeak.block must be false to prevent woken goroutines
+// from immediately going back to sleep.
+func gcWakeAllStrongFromWeak() {
+	lock(&work.strongFromWeak.lock)
+	list := work.strongFromWeak.q.popList()
+	injectglist(&list)
+	unlock(&work.strongFromWeak.lock)
+}
+
 // Retrieves or creates a weak pointer handle for the object p.
 func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 	// First try to retrieve without allocating.
 	if handle := getWeakHandle(p); handle != nil {
+		// Keep p alive for the duration of the function to ensure
+		// that it cannot die while we're trying to do this.
+		KeepAlive(p)
 		return handle
 	}
 
@@ -2105,7 +2169,17 @@ func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 			scanblock(uintptr(unsafe.Pointer(&s.handle)), goarch.PtrSize, &oneptrmask[0], gcw, nil)
 			releasem(mp)
 		}
-		return s.handle
+
+		// Keep p alive for the duration of the function to ensure
+		// that it cannot die while we're trying to do this.
+		//
+		// Same for handle, which is only stored in the special.
+		// There's a window where it might die if we don't keep it
+		// alive explicitly. Returning it here is probably good enough,
+		// but let's be defensive and explicit. See #70455.
+		KeepAlive(p)
+		KeepAlive(handle)
+		return handle
 	}
 
 	// There was an existing handle. Free the special
@@ -2124,8 +2198,11 @@ func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 	}
 
 	// Keep p alive for the duration of the function to ensure
-	// that it cannot die while we're trying to this.
+	// that it cannot die while we're trying to do this.
+	//
+	// Same for handle, just to be defensive.
 	KeepAlive(p)
+	KeepAlive(handle)
 	return handle
 }
 
@@ -2154,6 +2231,9 @@ func getWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 	unlock(&span.speciallock)
 	releasem(mp)
 
+	// Keep p alive for the duration of the function to ensure
+	// that it cannot die while we're trying to do this.
+	KeepAlive(p)
 	return handle
 }
 
diff --git a/src/runtime/mklockrank.go b/src/runtime/mklockrank.go
index 1239b4a546ea39..3391afc6572509 100644
--- a/src/runtime/mklockrank.go
+++ b/src/runtime/mklockrank.go
@@ -50,6 +50,7 @@ NONE < defer;
 NONE <
   sweepWaiters,
   assistQueue,
+  strongFromWeakQueue,
   sweep;
 
 # Test only
@@ -66,6 +67,7 @@ assistQueue,
   hchan,
   pollDesc, # pollDesc can interact with timers, which can lock sched.
   scavenge,
+  strongFromWeakQueue,
   sweep,
   sweepWaiters,
   testR,
diff --git a/src/runtime/mprof.go b/src/runtime/mprof.go
index 006274757e66f1..ee3e59a9aa99ce 100644
--- a/src/runtime/mprof.go
+++ b/src/runtime/mprof.go
@@ -1136,11 +1136,12 @@ func expandFrames(p []BlockProfileRecord) {
 	for i := range p {
 		cf := CallersFrames(p[i].Stack())
 		j := 0
-		for ; j < len(expandedStack); j++ {
+		for j < len(expandedStack) {
 			f, more := cf.Next()
 			// f.PC is a "call PC", but later consumers will expect
 			// "return PCs"
 			expandedStack[j] = f.PC + 1
+			j++
 			if !more {
 				break
 			}
@@ -1270,7 +1271,8 @@ func pprof_mutexProfileInternal(p []profilerecord.BlockProfileRecord) (n int, ok
 // of calling ThreadCreateProfile directly.
 func ThreadCreateProfile(p []StackRecord) (n int, ok bool) {
 	return threadCreateProfileInternal(len(p), func(r profilerecord.StackRecord) {
-		copy(p[0].Stack0[:], r.Stack)
+		i := copy(p[0].Stack0[:], r.Stack)
+		clear(p[0].Stack0[i:])
 		p = p[1:]
 	})
 }
@@ -1649,7 +1651,8 @@ func GoroutineProfile(p []StackRecord) (n int, ok bool) {
 		return
 	}
 	for i, mr := range records[0:n] {
-		copy(p[i].Stack0[:], mr.Stack)
+		l := copy(p[i].Stack0[:], mr.Stack)
+		clear(p[i].Stack0[l:])
 	}
 	return
 }
diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index 6ce656c70e146e..e80d390e0d09f2 100644
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -879,8 +879,9 @@ func runPerThreadSyscall() {
 }
 
 const (
-	_SI_USER  = 0
-	_SI_TKILL = -6
+	_SI_USER     = 0
+	_SI_TKILL    = -6
+	_SYS_SECCOMP = 1
 )
 
 // sigFromUser reports whether the signal was sent because of a call
@@ -892,6 +893,14 @@ func (c *sigctxt) sigFromUser() bool {
 	return code == _SI_USER || code == _SI_TKILL
 }
 
+// sigFromSeccomp reports whether the signal was sent from seccomp.
+//
+//go:nosplit
+func (c *sigctxt) sigFromSeccomp() bool {
+	code := int32(c.sigcode())
+	return code == _SYS_SECCOMP
+}
+
 //go:nosplit
 func mprotect(addr unsafe.Pointer, n uintptr, prot int32) (ret int32, errno int32) {
 	r, _, err := syscall.Syscall6(syscall.SYS_MPROTECT, uintptr(addr), n, uintptr(prot), 0, 0, 0)
diff --git a/src/runtime/os_unix_nonlinux.go b/src/runtime/os_unix_nonlinux.go
index b98753b8fe12b7..0e8b61c3b11aa2 100644
--- a/src/runtime/os_unix_nonlinux.go
+++ b/src/runtime/os_unix_nonlinux.go
@@ -13,3 +13,10 @@ package runtime
 func (c *sigctxt) sigFromUser() bool {
 	return c.sigcode() == _SI_USER
 }
+
+// sigFromSeccomp reports whether the signal was sent from seccomp.
+//
+//go:nosplit
+func (c *sigctxt) sigFromSeccomp() bool {
+	return false
+}
diff --git a/src/runtime/pprof/mprof_test.go b/src/runtime/pprof/mprof_test.go
index 391588d4acd0ec..ef373b36848437 100644
--- a/src/runtime/pprof/mprof_test.go
+++ b/src/runtime/pprof/mprof_test.go
@@ -145,7 +145,7 @@ func TestMemoryProfiler(t *testing.T) {
 		}
 		t.Logf("Profile = %v", p)
 
-		stks := stacks(p)
+		stks := profileStacks(p)
 		for _, test := range tests {
 			if !containsStack(stks, test.stk) {
 				t.Fatalf("No matching stack entry for %q\n\nProfile:\n%v\n", test.stk, p)
diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index 30ef50b1c0fa7a..da4ad17d77e6fd 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -15,6 +15,7 @@ import (
 	"internal/syscall/unix"
 	"internal/testenv"
 	"io"
+	"iter"
 	"math"
 	"math/big"
 	"os"
@@ -981,7 +982,7 @@ func TestBlockProfile(t *testing.T) {
 			t.Fatalf("invalid profile: %v", err)
 		}
 
-		stks := stacks(p)
+		stks := profileStacks(p)
 		for _, test := range tests {
 			if !containsStack(stks, test.stk) {
 				t.Errorf("No matching stack entry for %v, want %+v", test.name, test.stk)
@@ -991,7 +992,7 @@ func TestBlockProfile(t *testing.T) {
 
 }
 
-func stacks(p *profile.Profile) (res [][]string) {
+func profileStacks(p *profile.Profile) (res [][]string) {
 	for _, s := range p.Sample {
 		var stk []string
 		for _, l := range s.Location {
@@ -1004,6 +1005,22 @@ func stacks(p *profile.Profile) (res [][]string) {
 	return res
 }
 
+func blockRecordStacks(records []runtime.BlockProfileRecord) (res [][]string) {
+	for _, record := range records {
+		frames := runtime.CallersFrames(record.Stack())
+		var stk []string
+		for {
+			frame, more := frames.Next()
+			stk = append(stk, frame.Function)
+			if !more {
+				break
+			}
+		}
+		res = append(res, stk)
+	}
+	return res
+}
+
 func containsStack(got [][]string, want []string) bool {
 	for _, stk := range got {
 		if len(stk) < len(want) {
@@ -1288,7 +1305,7 @@ func TestMutexProfile(t *testing.T) {
 			t.Fatalf("invalid profile: %v", err)
 		}
 
-		stks := stacks(p)
+		stks := profileStacks(p)
 		for _, want := range [][]string{
 			{"sync.(*Mutex).Unlock", "runtime/pprof.blockMutexN.func1"},
 		} {
@@ -1328,6 +1345,28 @@ func TestMutexProfile(t *testing.T) {
 			t.Fatalf("profile samples total %v, want within range [%v, %v] (target: %v)", d, lo, hi, N*D)
 		}
 	})
+
+	t.Run("records", func(t *testing.T) {
+		// Record a mutex profile using the structured record API.
+		var records []runtime.BlockProfileRecord
+		for {
+			n, ok := runtime.MutexProfile(records)
+			if ok {
+				records = records[:n]
+				break
+			}
+			records = make([]runtime.BlockProfileRecord, n*2)
+		}
+
+		// Check that we see the same stack trace as the proto profile. For
+		// historical reason we expect a runtime.goexit root frame here that is
+		// omitted in the proto profile.
+		stks := blockRecordStacks(records)
+		want := []string{"sync.(*Mutex).Unlock", "runtime/pprof.blockMutexN.func1", "runtime.goexit"}
+		if !containsStack(stks, want) {
+			t.Errorf("No matching stack entry for %+v", want)
+		}
+	})
 }
 
 func TestMutexProfileRateAdjust(t *testing.T) {
@@ -1754,6 +1793,50 @@ func TestGoroutineProfileConcurrency(t *testing.T) {
 	}
 }
 
+// Regression test for #69998.
+func TestGoroutineProfileCoro(t *testing.T) {
+	testenv.MustHaveParallelism(t)
+
+	goroutineProf := Lookup("goroutine")
+
+	// Set up a goroutine to just create and run coroutine goroutines all day.
+	iterFunc := func() {
+		p, stop := iter.Pull2(
+			func(yield func(int, int) bool) {
+				for i := 0; i < 10000; i++ {
+					if !yield(i, i) {
+						return
+					}
+				}
+			},
+		)
+		defer stop()
+		for {
+			_, _, ok := p()
+			if !ok {
+				break
+			}
+		}
+	}
+	var wg sync.WaitGroup
+	done := make(chan struct{})
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			iterFunc()
+			select {
+			case <-done:
+			default:
+			}
+		}
+	}()
+
+	// Take a goroutine profile. If the bug in #69998 is present, this will crash
+	// with high probability. We don't care about the output for this bug.
+	goroutineProf.WriteTo(io.Discard, 1)
+}
+
 func BenchmarkGoroutine(b *testing.B) {
 	withIdle := func(n int, fn func(b *testing.B)) func(b *testing.B) {
 		return func(b *testing.B) {
@@ -2441,16 +2524,7 @@ func TestTimeVDSO(t *testing.T) {
 }
 
 func TestProfilerStackDepth(t *testing.T) {
-	// Disable sampling, otherwise it's difficult to assert anything.
-	oldMemRate := runtime.MemProfileRate
-	runtime.MemProfileRate = 1
-	runtime.SetBlockProfileRate(1)
-	oldMutexRate := runtime.SetMutexProfileFraction(1)
-	t.Cleanup(func() {
-		runtime.MemProfileRate = oldMemRate
-		runtime.SetBlockProfileRate(0)
-		runtime.SetMutexProfileFraction(oldMutexRate)
-	})
+	t.Cleanup(disableSampling())
 
 	const depth = 128
 	go produceProfileEvents(t, depth)
@@ -2478,7 +2552,7 @@ func TestProfilerStackDepth(t *testing.T) {
 			}
 			t.Logf("Profile = %v", p)
 
-			stks := stacks(p)
+			stks := profileStacks(p)
 			var stk []string
 			for _, s := range stks {
 				if hasPrefix(s, test.prefix) {
@@ -2742,3 +2816,84 @@ runtime/pprof.inlineA`,
 		})
 	}
 }
+
+func TestProfileRecordNullPadding(t *testing.T) {
+	// Produce events for the different profile types.
+	t.Cleanup(disableSampling())
+	memSink = make([]byte, 1)      // MemProfile
+	<-time.After(time.Millisecond) // BlockProfile
+	blockMutex(t)                  // MutexProfile
+	runtime.GC()
+
+	// Test that all profile records are null padded.
+	testProfileRecordNullPadding(t, "MutexProfile", runtime.MutexProfile)
+	testProfileRecordNullPadding(t, "GoroutineProfile", runtime.GoroutineProfile)
+	testProfileRecordNullPadding(t, "BlockProfile", runtime.BlockProfile)
+	testProfileRecordNullPadding(t, "MemProfile/inUseZero=true", func(p []runtime.MemProfileRecord) (int, bool) {
+		return runtime.MemProfile(p, true)
+	})
+	testProfileRecordNullPadding(t, "MemProfile/inUseZero=false", func(p []runtime.MemProfileRecord) (int, bool) {
+		return runtime.MemProfile(p, false)
+	})
+	// Not testing ThreadCreateProfile because it is broken, see issue 6104.
+}
+
+func testProfileRecordNullPadding[T runtime.StackRecord | runtime.MemProfileRecord | runtime.BlockProfileRecord](t *testing.T, name string, fn func([]T) (int, bool)) {
+	stack0 := func(sr *T) *[32]uintptr {
+		switch t := any(sr).(type) {
+		case *runtime.StackRecord:
+			return &t.Stack0
+		case *runtime.MemProfileRecord:
+			return &t.Stack0
+		case *runtime.BlockProfileRecord:
+			return &t.Stack0
+		default:
+			panic(fmt.Sprintf("unexpected type %T", sr))
+		}
+	}
+
+	t.Run(name, func(t *testing.T) {
+		var p []T
+		for {
+			n, ok := fn(p)
+			if ok {
+				p = p[:n]
+				break
+			}
+			p = make([]T, n*2)
+			for i := range p {
+				s0 := stack0(&p[i])
+				for j := range s0 {
+					// Poison the Stack0 array to identify lack of zero padding
+					s0[j] = ^uintptr(0)
+				}
+			}
+		}
+
+		if len(p) == 0 {
+			t.Fatal("no records found")
+		}
+
+		for _, sr := range p {
+			for i, v := range stack0(&sr) {
+				if v == ^uintptr(0) {
+					t.Fatalf("record p[%d].Stack0 is not null padded: %+v", i, sr)
+				}
+			}
+		}
+	})
+}
+
+// disableSampling configures the profilers to capture all events, otherwise
+// it's difficult to assert anything.
+func disableSampling() func() {
+	oldMemRate := runtime.MemProfileRate
+	runtime.MemProfileRate = 1
+	runtime.SetBlockProfileRate(1)
+	oldMutexRate := runtime.SetMutexProfileFraction(1)
+	return func() {
+		runtime.MemProfileRate = oldMemRate
+		runtime.SetBlockProfileRate(0)
+		runtime.SetMutexProfileFraction(oldMutexRate)
+	}
+}
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index c4f175b0b76b22..e5bf3ff4f0bfc0 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -1137,6 +1137,11 @@ func casfrom_Gscanstatus(gp *g, oldval, newval uint32) {
 		dumpgstatus(gp)
 		throw("casfrom_Gscanstatus: gp->status is not in scan state")
 	}
+	// We're transitioning into the running state, record the timestamp for
+	// subsequent use.
+	if newval == _Grunning {
+		gp.lastsched = nanotime()
+	}
 	releaseLockRankAndM(lockRankGscan)
 }
 
@@ -1152,6 +1157,11 @@ func castogscanstatus(gp *g, oldval, newval uint32) bool {
 			r := gp.atomicstatus.CompareAndSwap(oldval, newval)
 			if r {
 				acquireLockRankAndM(lockRankGscan)
+				// We're transitioning out of running, record how long we were in the
+				// state.
+				if oldval == _Grunning {
+					gp.runningnanos += nanotime() - gp.lastsched
+				}
 			}
 			return r
 
@@ -1211,7 +1221,18 @@ func casgstatus(gp *g, oldval, newval uint32) {
 		}
 	}
 
+	now := nanotime()
+	if newval == _Grunning {
+		// We're transitioning into the running state, record the timestamp for
+		// subsequent use.
+		gp.lastsched = now
+	}
+
 	if oldval == _Grunning {
+		// We're transitioning out of running, record how long we were in the
+		// state.
+		gp.runningnanos += now - gp.lastsched
+
 		// Track every gTrackingPeriod time a goroutine transitions out of running.
 		if casgstatusAlwaysTrack || gp.trackingSeq%gTrackingPeriod == 0 {
 			gp.tracking = true
@@ -1232,7 +1253,6 @@ func casgstatus(gp *g, oldval, newval uint32) {
 		// We transitioned out of runnable, so measure how much
 		// time we spent in this state and add it to
 		// runnableTime.
-		now := nanotime()
 		gp.runnableTime += now - gp.trackingStamp
 		gp.trackingStamp = 0
 	case _Gwaiting:
@@ -1245,7 +1265,6 @@ func casgstatus(gp *g, oldval, newval uint32) {
 		// a more representative estimate of the absolute value.
 		// gTrackingPeriod also represents an accurate sampling period
 		// because we can only enter this state from _Grunning.
-		now := nanotime()
 		sched.totalMutexWaitTime.Add((now - gp.trackingStamp) * gTrackingPeriod)
 		gp.trackingStamp = 0
 	}
@@ -1256,12 +1275,10 @@ func casgstatus(gp *g, oldval, newval uint32) {
 			break
 		}
 		// Blocking on a lock. Write down the timestamp.
-		now := nanotime()
 		gp.trackingStamp = now
 	case _Grunnable:
 		// We just transitioned into runnable, so record what
 		// time that happened.
-		now := nanotime()
 		gp.trackingStamp = now
 	case _Grunning:
 		// We're transitioning into running, so turn off
@@ -1323,6 +1340,9 @@ func casGToPreemptScan(gp *g, old, new uint32) {
 	acquireLockRankAndM(lockRankGscan)
 	for !gp.atomicstatus.CompareAndSwap(_Grunning, _Gscan|_Gpreempted) {
 	}
+	// We're transitioning out of running, record how long we were in the
+	// state.
+	gp.runningnanos += nanotime() - gp.lastsched
 }
 
 // casGFromPreempted attempts to transition gp from _Gpreempted to
@@ -2539,6 +2559,7 @@ func dropm() {
 	g0.stack.lo = 0
 	g0.stackguard0 = 0
 	g0.stackguard1 = 0
+	mp.g0StackAccurate = false
 
 	putExtraM(mp)
 
@@ -3872,23 +3893,23 @@ func injectglist(glist *gList) {
 	if glist.empty() {
 		return
 	}
-	trace := traceAcquire()
-	if trace.ok() {
-		for gp := glist.head.ptr(); gp != nil; gp = gp.schedlink.ptr() {
-			trace.GoUnpark(gp, 0)
-		}
-		traceRelease(trace)
-	}
 
 	// Mark all the goroutines as runnable before we put them
 	// on the run queues.
 	head := glist.head.ptr()
 	var tail *g
 	qsize := 0
+	trace := traceAcquire()
 	for gp := head; gp != nil; gp = gp.schedlink.ptr() {
 		tail = gp
 		qsize++
 		casgstatus(gp, _Gwaiting, _Grunnable)
+		if trace.ok() {
+			trace.GoUnpark(gp, 0)
+		}
+	}
+	if trace.ok() {
+		traceRelease(trace)
 	}
 
 	// Turn the gList into a gQueue.
@@ -4059,6 +4080,14 @@ func dropg() {
 	setGNoWB(&gp.m.curg, nil)
 }
 
+// Grunningnanos returns the wall time spent by current g in the running state.
+// A goroutine may be running on an OS thread that's descheduled by the OS
+// scheduler, this time still counts towards the metric.
+func Grunningnanos() int64 {
+	gp := getg()
+	return gp.runningnanos + nanotime() - gp.lastsched
+}
+
 func parkunlock_c(gp *g, lock unsafe.Pointer) bool {
 	unlock((*mutex)(lock))
 	return true
@@ -4290,6 +4319,8 @@ func gdestroy(gp *g) {
 	gp.param = nil
 	gp.labels = nil
 	gp.timer = nil
+	gp.lastsched = 0
+	gp.runningnanos = 0
 
 	if gcBlackenEnabled != 0 && gp.gcAssistBytes > 0 {
 		// Flush assist credit to the global pool. This gives
@@ -4415,7 +4446,13 @@ func reentersyscall(pc, sp, bp uintptr) {
 	}
 	if gp.syscallsp < gp.stack.lo || gp.stack.hi < gp.syscallsp {
 		systemstack(func() {
-			print("entersyscall inconsistent ", hex(gp.syscallsp), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
+			print("entersyscall inconsistent sp ", hex(gp.syscallsp), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
+			throw("entersyscall")
+		})
+	}
+	if gp.syscallbp != 0 && gp.syscallbp < gp.stack.lo || gp.stack.hi < gp.syscallbp {
+		systemstack(func() {
+			print("entersyscall inconsistent bp ", hex(gp.syscallbp), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
 			throw("entersyscall")
 		})
 	}
@@ -4553,14 +4590,20 @@ func entersyscallblock() {
 		sp2 := gp.sched.sp
 		sp3 := gp.syscallsp
 		systemstack(func() {
-			print("entersyscallblock inconsistent ", hex(sp1), " ", hex(sp2), " ", hex(sp3), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
+			print("entersyscallblock inconsistent sp ", hex(sp1), " ", hex(sp2), " ", hex(sp3), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
 			throw("entersyscallblock")
 		})
 	}
 	casgstatus(gp, _Grunning, _Gsyscall)
 	if gp.syscallsp < gp.stack.lo || gp.stack.hi < gp.syscallsp {
 		systemstack(func() {
-			print("entersyscallblock inconsistent ", hex(sp), " ", hex(gp.sched.sp), " ", hex(gp.syscallsp), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
+			print("entersyscallblock inconsistent sp ", hex(sp), " ", hex(gp.sched.sp), " ", hex(gp.syscallsp), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
+			throw("entersyscallblock")
+		})
+	}
+	if gp.syscallbp != 0 && gp.syscallbp < gp.stack.lo || gp.stack.hi < gp.syscallbp {
+		systemstack(func() {
+			print("entersyscallblock inconsistent bp ", hex(bp), " ", hex(gp.sched.bp), " ", hex(gp.syscallbp), " [", hex(gp.stack.lo), ",", hex(gp.stack.hi), "]\n")
 			throw("entersyscallblock")
 		})
 	}
diff --git a/src/runtime/rt0_aix_ppc64.s b/src/runtime/rt0_aix_ppc64.s
index 1670a809862a2b..74c57bb1dc9136 100644
--- a/src/runtime/rt0_aix_ppc64.s
+++ b/src/runtime/rt0_aix_ppc64.s
@@ -41,6 +41,8 @@ TEXT _main(SB),NOSPLIT,$-8
 	MOVD R12, CTR
 	BR (CTR)
 
+// Paramater save space required to cross-call into _cgo_sys_thread_create
+#define PARAM_SPACE 16
 
 TEXT _rt0_ppc64_aix_lib(SB),NOSPLIT,$-8
 	// Start with standard C stack frame layout and linkage.
@@ -49,45 +51,45 @@ TEXT _rt0_ppc64_aix_lib(SB),NOSPLIT,$-8
 	MOVW	CR, R0	   // Save CR in caller's frame
 	MOVD	R0, 8(R1)
 
-	MOVDU	R1, -344(R1) // Allocate frame.
+	MOVDU	R1, -344-PARAM_SPACE(R1) // Allocate frame.
 
 	// Preserve callee-save registers.
-	MOVD	R14, 48(R1)
-	MOVD	R15, 56(R1)
-	MOVD	R16, 64(R1)
-	MOVD	R17, 72(R1)
-	MOVD	R18, 80(R1)
-	MOVD	R19, 88(R1)
-	MOVD	R20, 96(R1)
-	MOVD	R21,104(R1)
-	MOVD	R22, 112(R1)
-	MOVD	R23, 120(R1)
-	MOVD	R24, 128(R1)
-	MOVD	R25, 136(R1)
-	MOVD	R26, 144(R1)
-	MOVD	R27, 152(R1)
-	MOVD	R28, 160(R1)
-	MOVD	R29, 168(R1)
-	MOVD	g, 176(R1) // R30
-	MOVD	R31, 184(R1)
-	FMOVD	F14, 192(R1)
-	FMOVD	F15, 200(R1)
-	FMOVD	F16, 208(R1)
-	FMOVD	F17, 216(R1)
-	FMOVD	F18, 224(R1)
-	FMOVD	F19, 232(R1)
-	FMOVD	F20, 240(R1)
-	FMOVD	F21, 248(R1)
-	FMOVD	F22, 256(R1)
-	FMOVD	F23, 264(R1)
-	FMOVD	F24, 272(R1)
-	FMOVD	F25, 280(R1)
-	FMOVD	F26, 288(R1)
-	FMOVD	F27, 296(R1)
-	FMOVD	F28, 304(R1)
-	FMOVD	F29, 312(R1)
-	FMOVD	F30, 320(R1)
-	FMOVD	F31, 328(R1)
+	MOVD	R14, 48+PARAM_SPACE(R1)
+	MOVD	R15, 56+PARAM_SPACE(R1)
+	MOVD	R16, 64+PARAM_SPACE(R1)
+	MOVD	R17, 72+PARAM_SPACE(R1)
+	MOVD	R18, 80+PARAM_SPACE(R1)
+	MOVD	R19, 88+PARAM_SPACE(R1)
+	MOVD	R20, 96+PARAM_SPACE(R1)
+	MOVD	R21,104+PARAM_SPACE(R1)
+	MOVD	R22, 112+PARAM_SPACE(R1)
+	MOVD	R23, 120+PARAM_SPACE(R1)
+	MOVD	R24, 128+PARAM_SPACE(R1)
+	MOVD	R25, 136+PARAM_SPACE(R1)
+	MOVD	R26, 144+PARAM_SPACE(R1)
+	MOVD	R27, 152+PARAM_SPACE(R1)
+	MOVD	R28, 160+PARAM_SPACE(R1)
+	MOVD	R29, 168+PARAM_SPACE(R1)
+	MOVD	g, 176+PARAM_SPACE(R1) // R30
+	MOVD	R31, 184+PARAM_SPACE(R1)
+	FMOVD	F14, 192+PARAM_SPACE(R1)
+	FMOVD	F15, 200+PARAM_SPACE(R1)
+	FMOVD	F16, 208+PARAM_SPACE(R1)
+	FMOVD	F17, 216+PARAM_SPACE(R1)
+	FMOVD	F18, 224+PARAM_SPACE(R1)
+	FMOVD	F19, 232+PARAM_SPACE(R1)
+	FMOVD	F20, 240+PARAM_SPACE(R1)
+	FMOVD	F21, 248+PARAM_SPACE(R1)
+	FMOVD	F22, 256+PARAM_SPACE(R1)
+	FMOVD	F23, 264+PARAM_SPACE(R1)
+	FMOVD	F24, 272+PARAM_SPACE(R1)
+	FMOVD	F25, 280+PARAM_SPACE(R1)
+	FMOVD	F26, 288+PARAM_SPACE(R1)
+	FMOVD	F27, 296+PARAM_SPACE(R1)
+	FMOVD	F28, 304+PARAM_SPACE(R1)
+	FMOVD	F29, 312+PARAM_SPACE(R1)
+	FMOVD	F30, 320+PARAM_SPACE(R1)
+	FMOVD	F31, 328+PARAM_SPACE(R1)
 
 	// Synchronous initialization.
 	MOVD	$runtime·reginit(SB), R12
@@ -130,44 +132,44 @@ nocgo:
 
 done:
 	// Restore saved registers.
-	MOVD	48(R1), R14
-	MOVD	56(R1), R15
-	MOVD	64(R1), R16
-	MOVD	72(R1), R17
-	MOVD	80(R1), R18
-	MOVD	88(R1), R19
-	MOVD	96(R1), R20
-	MOVD	104(R1), R21
-	MOVD	112(R1), R22
-	MOVD	120(R1), R23
-	MOVD	128(R1), R24
-	MOVD	136(R1), R25
-	MOVD	144(R1), R26
-	MOVD	152(R1), R27
-	MOVD	160(R1), R28
-	MOVD	168(R1), R29
-	MOVD	176(R1), g // R30
-	MOVD	184(R1), R31
-	FMOVD	196(R1), F14
-	FMOVD	200(R1), F15
-	FMOVD	208(R1), F16
-	FMOVD	216(R1), F17
-	FMOVD	224(R1), F18
-	FMOVD	232(R1), F19
-	FMOVD	240(R1), F20
-	FMOVD	248(R1), F21
-	FMOVD	256(R1), F22
-	FMOVD	264(R1), F23
-	FMOVD	272(R1), F24
-	FMOVD	280(R1), F25
-	FMOVD	288(R1), F26
-	FMOVD	296(R1), F27
-	FMOVD	304(R1), F28
-	FMOVD	312(R1), F29
-	FMOVD	320(R1), F30
-	FMOVD	328(R1), F31
-
-	ADD	$344, R1
+	MOVD	48+PARAM_SPACE(R1), R14
+	MOVD	56+PARAM_SPACE(R1), R15
+	MOVD	64+PARAM_SPACE(R1), R16
+	MOVD	72+PARAM_SPACE(R1), R17
+	MOVD	80+PARAM_SPACE(R1), R18
+	MOVD	88+PARAM_SPACE(R1), R19
+	MOVD	96+PARAM_SPACE(R1), R20
+	MOVD	104+PARAM_SPACE(R1), R21
+	MOVD	112+PARAM_SPACE(R1), R22
+	MOVD	120+PARAM_SPACE(R1), R23
+	MOVD	128+PARAM_SPACE(R1), R24
+	MOVD	136+PARAM_SPACE(R1), R25
+	MOVD	144+PARAM_SPACE(R1), R26
+	MOVD	152+PARAM_SPACE(R1), R27
+	MOVD	160+PARAM_SPACE(R1), R28
+	MOVD	168+PARAM_SPACE(R1), R29
+	MOVD	176+PARAM_SPACE(R1), g // R30
+	MOVD	184+PARAM_SPACE(R1), R31
+	FMOVD	196+PARAM_SPACE(R1), F14
+	FMOVD	200+PARAM_SPACE(R1), F15
+	FMOVD	208+PARAM_SPACE(R1), F16
+	FMOVD	216+PARAM_SPACE(R1), F17
+	FMOVD	224+PARAM_SPACE(R1), F18
+	FMOVD	232+PARAM_SPACE(R1), F19
+	FMOVD	240+PARAM_SPACE(R1), F20
+	FMOVD	248+PARAM_SPACE(R1), F21
+	FMOVD	256+PARAM_SPACE(R1), F22
+	FMOVD	264+PARAM_SPACE(R1), F23
+	FMOVD	272+PARAM_SPACE(R1), F24
+	FMOVD	280+PARAM_SPACE(R1), F25
+	FMOVD	288+PARAM_SPACE(R1), F26
+	FMOVD	296+PARAM_SPACE(R1), F27
+	FMOVD	304+PARAM_SPACE(R1), F28
+	FMOVD	312+PARAM_SPACE(R1), F29
+	FMOVD	320+PARAM_SPACE(R1), F30
+	FMOVD	328+PARAM_SPACE(R1), F31
+
+	ADD	$344+PARAM_SPACE, R1
 
 	MOVD	8(R1), R0
 	MOVFL	R0, $0xff
diff --git a/src/runtime/runtime-gdb_test.go b/src/runtime/runtime-gdb_test.go
index 5defe2f615eaa4..14561330bbf281 100644
--- a/src/runtime/runtime-gdb_test.go
+++ b/src/runtime/runtime-gdb_test.go
@@ -575,15 +575,15 @@ func TestGdbAutotmpTypes(t *testing.T) {
 
 	// Check that the backtrace matches the source code.
 	types := []string{
-		"[]main.astruct;",
-		"bucket<string,main.astruct>;",
-		"hash<string,main.astruct>;",
-		"main.astruct;",
-		"hash<string,main.astruct> * map[string]main.astruct;",
+		"[]main.astruct",
+		"bucket<string,main.astruct>",
+		"hash<string,main.astruct>",
+		"main.astruct",
+		"hash<string,main.astruct> * map[string]main.astruct",
 	}
 	for _, name := range types {
 		if !strings.Contains(sgot, name) {
-			t.Fatalf("could not find %s in 'info typrs astruct' output", name)
+			t.Fatalf("could not find %q in 'info typrs astruct' output", name)
 		}
 	}
 }
diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go
index 03ef74b8dc4b54..cb45504fbfc8ec 100644
--- a/src/runtime/runtime1.go
+++ b/src/runtime/runtime1.go
@@ -316,6 +316,7 @@ var debug struct {
 	gcpacertrace             int32
 	gcshrinkstackoff         int32
 	gcstoptheworld           int32
+	gcnoassist               int32
 	gctrace                  int32
 	invalidptr               int32
 	madvdontneed             int32 // for Linux; issue 28466
@@ -374,6 +375,7 @@ var dbgvars = []*dbgVar{
 	{name: "gcpacertrace", value: &debug.gcpacertrace},
 	{name: "gcshrinkstackoff", value: &debug.gcshrinkstackoff},
 	{name: "gcstoptheworld", value: &debug.gcstoptheworld},
+	{name: "gcnoassist", value: &debug.gcnoassist},
 	{name: "gctrace", value: &debug.gctrace},
 	{name: "harddecommit", value: &debug.harddecommit},
 	{name: "inittrace", value: &debug.inittrace},
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 4a789639611fb7..65051c55351c16 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -493,7 +493,6 @@ type g struct {
 	trackingStamp int64 // timestamp of when the G last started being tracked
 	runnableTime  int64 // the amount of time spent runnable, cleared when running, only used when tracking
 	lockedm       muintptr
-	sig           uint32
 	writebuf      []byte
 	sigcode0      uintptr
 	sigcode1      uintptr
@@ -509,6 +508,10 @@ type g struct {
 	timer         *timer         // cached timer for time.Sleep
 	sleepWhen     int64          // when to sleep until
 	selectDone    atomic.Uint32  // are we participating in a select and did someone win the race?
+	sig           uint32
+	lastsched     int64 // timestamp when the G last started running
+	runningnanos  int64 // wall time spent in the running state
+
 
 	// goroutineProfiled indicates the status of this goroutine's stack for the
 	// current in-progress goroutine profile
@@ -556,47 +559,48 @@ type m struct {
 	_       uint32 // align next field to 8 bytes
 
 	// Fields not known to debuggers.
-	procid        uint64            // for debuggers, but offset not hard-coded
-	gsignal       *g                // signal-handling g
-	goSigStack    gsignalStack      // Go-allocated signal handling stack
-	sigmask       sigset            // storage for saved signal mask
-	tls           [tlsSlots]uintptr // thread-local storage (for x86 extern register)
-	mstartfn      func()
-	curg          *g       // current running goroutine
-	caughtsig     guintptr // goroutine running during fatal signal
-	p             puintptr // attached p for executing go code (nil if not executing go code)
-	nextp         puintptr
-	oldp          puintptr // the p that was attached before executing a syscall
-	id            int64
-	mallocing     int32
-	throwing      throwType
-	preemptoff    string // if != "", keep curg running on this m
-	locks         int32
-	dying         int32
-	profilehz     int32
-	spinning      bool // m is out of work and is actively looking for work
-	blocked       bool // m is blocked on a note
-	newSigstack   bool // minit on C thread called sigaltstack
-	printlock     int8
-	incgo         bool          // m is executing a cgo call
-	isextra       bool          // m is an extra m
-	isExtraInC    bool          // m is an extra m that is not executing Go code
-	isExtraInSig  bool          // m is an extra m in a signal handler
-	freeWait      atomic.Uint32 // Whether it is safe to free g0 and delete m (one of freeMRef, freeMStack, freeMWait)
-	needextram    bool
-	traceback     uint8
-	ncgocall      uint64        // number of cgo calls in total
-	ncgo          int32         // number of cgo calls currently in progress
-	cgoCallersUse atomic.Uint32 // if non-zero, cgoCallers in use temporarily
-	cgoCallers    *cgoCallers   // cgo traceback if crashing in cgo call
-	park          note
-	alllink       *m // on allm
-	schedlink     muintptr
-	lockedg       guintptr
-	createstack   [32]uintptr // stack that created this thread, it's used for StackRecord.Stack0, so it must align with it.
-	lockedExt     uint32      // tracking for external LockOSThread
-	lockedInt     uint32      // tracking for internal lockOSThread
-	nextwaitm     muintptr    // next m waiting for lock
+	procid          uint64            // for debuggers, but offset not hard-coded
+	gsignal         *g                // signal-handling g
+	goSigStack      gsignalStack      // Go-allocated signal handling stack
+	sigmask         sigset            // storage for saved signal mask
+	tls             [tlsSlots]uintptr // thread-local storage (for x86 extern register)
+	mstartfn        func()
+	curg            *g       // current running goroutine
+	caughtsig       guintptr // goroutine running during fatal signal
+	p               puintptr // attached p for executing go code (nil if not executing go code)
+	nextp           puintptr
+	oldp            puintptr // the p that was attached before executing a syscall
+	id              int64
+	mallocing       int32
+	throwing        throwType
+	preemptoff      string // if != "", keep curg running on this m
+	locks           int32
+	dying           int32
+	profilehz       int32
+	spinning        bool // m is out of work and is actively looking for work
+	blocked         bool // m is blocked on a note
+	newSigstack     bool // minit on C thread called sigaltstack
+	printlock       int8
+	incgo           bool          // m is executing a cgo call
+	isextra         bool          // m is an extra m
+	isExtraInC      bool          // m is an extra m that is not executing Go code
+	isExtraInSig    bool          // m is an extra m in a signal handler
+	freeWait        atomic.Uint32 // Whether it is safe to free g0 and delete m (one of freeMRef, freeMStack, freeMWait)
+	needextram      bool
+	g0StackAccurate bool // whether the g0 stack has accurate bounds
+	traceback       uint8
+	ncgocall        uint64        // number of cgo calls in total
+	ncgo            int32         // number of cgo calls currently in progress
+	cgoCallersUse   atomic.Uint32 // if non-zero, cgoCallers in use temporarily
+	cgoCallers      *cgoCallers   // cgo traceback if crashing in cgo call
+	park            note
+	alllink         *m // on allm
+	schedlink       muintptr
+	lockedg         guintptr
+	createstack     [32]uintptr // stack that created this thread, it's used for StackRecord.Stack0, so it must align with it.
+	lockedExt       uint32      // tracking for external LockOSThread
+	lockedInt       uint32      // tracking for internal lockOSThread
+	nextwaitm       muintptr    // next m waiting for lock
 
 	mLockProfile mLockProfile // fields relating to runtime.lock contention
 	profStack    []uintptr    // used for memory/block/mutex stack traces
@@ -768,6 +772,10 @@ type p struct {
 	// gcStopTime is the nanotime timestamp that this P last entered _Pgcstop.
 	gcStopTime int64
 
+	// ptrWrites counts non-nil heap pointer writes made on this P.
+	// Only modified if goexperiment.CgoCheck2 is enabled.
+	ptrWrites uint64
+
 	// Padding is no longer needed. False sharing is now not a worry because p is large enough
 	// that its size class is an integer multiple of the cache line size (for any of our architectures).
 }
@@ -1095,6 +1103,7 @@ const (
 	waitReasonTraceProcStatus                         // "trace proc status"
 	waitReasonPageTraceFlush                          // "page trace flush"
 	waitReasonCoroutine                               // "coroutine"
+	waitReasonGCWeakToStrongWait                      // "GC weak to strong wait"
 )
 
 var waitReasonStrings = [...]string{
@@ -1135,6 +1144,7 @@ var waitReasonStrings = [...]string{
 	waitReasonTraceProcStatus:       "trace proc status",
 	waitReasonPageTraceFlush:        "page trace flush",
 	waitReasonCoroutine:             "coroutine",
+	waitReasonGCWeakToStrongWait:    "GC weak to strong wait",
 }
 
 func (w waitReason) String() string {
@@ -1189,6 +1199,7 @@ var (
 
 	// len(allp) == gomaxprocs; may change at safe points, otherwise
 	// immutable.
+	//go:linkname allp
 	allp []*p
 
 	// Bitmask of Ps in _Pidle list, one bit per P. Reads and writes must
diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index 8ba498bdb238d5..6f40f440e807f8 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -605,6 +605,19 @@ var crashing atomic.Int32
 var testSigtrap func(info *siginfo, ctxt *sigctxt, gp *g) bool
 var testSigusr1 func(gp *g) bool
 
+// sigsysIgnored is non-zero if we are currently ignoring SIGSYS. See issue #69065.
+var sigsysIgnored uint32
+
+//go:linkname ignoreSIGSYS os.ignoreSIGSYS
+func ignoreSIGSYS() {
+	atomic.Store(&sigsysIgnored, 1)
+}
+
+//go:linkname restoreSIGSYS os.restoreSIGSYS
+func restoreSIGSYS() {
+	atomic.Store(&sigsysIgnored, 0)
+}
+
 // sighandler is invoked when a signal occurs. The global g will be
 // set to a gsignal goroutine and we will be running on the alternate
 // signal stack. The parameter gp will be the value of the global g
@@ -715,6 +728,10 @@ func sighandler(sig uint32, info *siginfo, ctxt unsafe.Pointer, gp *g) {
 		return
 	}
 
+	if sig == _SIGSYS && c.sigFromSeccomp() && atomic.Load(&sigsysIgnored) != 0 {
+		return
+	}
+
 	if flags&_SigKill != 0 {
 		dieFromSignal(sig)
 	}
diff --git a/src/runtime/sizeof_test.go b/src/runtime/sizeof_test.go
index 43aba98dcebcdb..a076c93b8e8df9 100644
--- a/src/runtime/sizeof_test.go
+++ b/src/runtime/sizeof_test.go
@@ -20,7 +20,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr // size on 32bit platforms
 		_64bit uintptr // size on 64bit platforms
 	}{
-		{runtime.G{}, 272, 432},   // g, but exported for testing
+		{runtime.G{}, 272, 448},   // g, but exported for testing
 		{runtime.Sudog{}, 56, 88}, // sudog, but exported for testing
 	}
 
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index cdf859a7ff1342..d43c6ace4ffcf2 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -69,7 +69,7 @@ const (
 	// to each stack below the usual guard area for OS-specific
 	// purposes like signal handling. Used on Windows, Plan 9,
 	// and iOS because they do not use a separate stack.
-	stackSystem = goos.IsWindows*512*goarch.PtrSize + goos.IsPlan9*512 + goos.IsIos*goarch.IsArm64*1024
+	stackSystem = goos.IsWindows*4096 + goos.IsPlan9*512 + goos.IsIos*goarch.IsArm64*1024
 
 	// The minimum size of stack used by Go code
 	stackMin = 2048
@@ -1330,7 +1330,7 @@ func morestackc() {
 }
 
 // startingStackSize is the amount of stack that new goroutines start with.
-// It is a power of 2, and between _FixedStack and maxstacksize, inclusive.
+// It is a power of 2, and between fixedStack and maxstacksize, inclusive.
 // startingStackSize is updated every GC by tracking the average size of
 // stacks scanned during the GC.
 var startingStackSize uint32 = fixedStack
diff --git a/src/runtime/syscall_windows.go b/src/runtime/syscall_windows.go
index 69d720a395c48d..85b1b8c9024a73 100644
--- a/src/runtime/syscall_windows.go
+++ b/src/runtime/syscall_windows.go
@@ -454,43 +454,37 @@ func syscall_getprocaddress(handle uintptr, procname *byte) (outhandle, err uint
 //go:linkname syscall_Syscall syscall.Syscall
 //go:nosplit
 func syscall_Syscall(fn, nargs, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
-	args := [...]uintptr{a1, a2, a3}
-	return syscall_SyscallN(fn, args[:nargs]...)
+	return syscall_syscalln(fn, nargs, a1, a2, a3)
 }
 
 //go:linkname syscall_Syscall6 syscall.Syscall6
 //go:nosplit
 func syscall_Syscall6(fn, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr) {
-	args := [...]uintptr{a1, a2, a3, a4, a5, a6}
-	return syscall_SyscallN(fn, args[:nargs]...)
+	return syscall_syscalln(fn, nargs, a1, a2, a3, a4, a5, a6)
 }
 
 //go:linkname syscall_Syscall9 syscall.Syscall9
 //go:nosplit
 func syscall_Syscall9(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2, err uintptr) {
-	args := [...]uintptr{a1, a2, a3, a4, a5, a6, a7, a8, a9}
-	return syscall_SyscallN(fn, args[:nargs]...)
+	return syscall_syscalln(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9)
 }
 
 //go:linkname syscall_Syscall12 syscall.Syscall12
 //go:nosplit
 func syscall_Syscall12(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12 uintptr) (r1, r2, err uintptr) {
-	args := [...]uintptr{a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12}
-	return syscall_SyscallN(fn, args[:nargs]...)
+	return syscall_syscalln(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12)
 }
 
 //go:linkname syscall_Syscall15 syscall.Syscall15
 //go:nosplit
 func syscall_Syscall15(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr) (r1, r2, err uintptr) {
-	args := [...]uintptr{a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15}
-	return syscall_SyscallN(fn, args[:nargs]...)
+	return syscall_syscalln(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15)
 }
 
 //go:linkname syscall_Syscall18 syscall.Syscall18
 //go:nosplit
 func syscall_Syscall18(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18 uintptr) (r1, r2, err uintptr) {
-	args := [...]uintptr{a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18}
-	return syscall_SyscallN(fn, args[:nargs]...)
+	return syscall_syscalln(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18)
 }
 
 // maxArgs should be divisible by 2, as Windows stack
@@ -503,7 +497,15 @@ const maxArgs = 42
 //go:linkname syscall_SyscallN syscall.SyscallN
 //go:nosplit
 func syscall_SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
-	if len(args) > maxArgs {
+	return syscall_syscalln(fn, uintptr(len(args)), args...)
+}
+
+//go:nosplit
+func syscall_syscalln(fn, n uintptr, args ...uintptr) (r1, r2, err uintptr) {
+	if n > uintptr(len(args)) {
+		panic("syscall: n > len(args)") // should not be reachable from user code
+	}
+	if n > maxArgs {
 		panic("runtime: SyscallN has too many arguments")
 	}
 
@@ -512,7 +514,7 @@ func syscall_SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
 	// calls back into Go.
 	c := &getg().m.winsyscall
 	c.fn = fn
-	c.n = uintptr(len(args))
+	c.n = n
 	if c.n != 0 {
 		c.args = uintptr(noescape(unsafe.Pointer(&args[0])))
 	}
diff --git a/src/runtime/syscall_windows_test.go b/src/runtime/syscall_windows_test.go
index 6a056c8d2b190c..156cf3eb8e5c71 100644
--- a/src/runtime/syscall_windows_test.go
+++ b/src/runtime/syscall_windows_test.go
@@ -1212,6 +1212,13 @@ func TestBigStackCallbackSyscall(t *testing.T) {
 	}
 }
 
+func TestSyscallStackUsage(t *testing.T) {
+	// Test that the stack usage of a syscall doesn't exceed the limit.
+	// See https://go.dev/issue/69813.
+	syscall.Syscall15(procSetEvent.Addr(), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
+	syscall.Syscall18(procSetEvent.Addr(), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
+}
+
 var (
 	modwinmm    = syscall.NewLazyDLL("winmm.dll")
 	modkernel32 = syscall.NewLazyDLL("kernel32.dll")
diff --git a/src/runtime/time.go b/src/runtime/time.go
index fc664f49eb8d7c..7b344a349610d3 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -26,10 +26,11 @@ type timer struct {
 	// mu protects reads and writes to all fields, with exceptions noted below.
 	mu mutex
 
-	astate  atomic.Uint8 // atomic copy of state bits at last unlock
-	state   uint8        // state bits
-	isChan  bool         // timer has a channel; immutable; can be read without lock
-	blocked uint32       // number of goroutines blocked on timer's channel
+	astate atomic.Uint8 // atomic copy of state bits at last unlock
+	state  uint8        // state bits
+	isChan bool         // timer has a channel; immutable; can be read without lock
+
+	blocked uint32 // number of goroutines blocked on timer's channel
 
 	// Timer wakes up at when, and then at when+period, ... (period > 0 only)
 	// each time calling f(arg, seq, delay) in the timer goroutine, so f must be
@@ -68,6 +69,20 @@ type timer struct {
 	// sendLock protects sends on the timer's channel.
 	// Not used for async (pre-Go 1.23) behavior when debug.asynctimerchan.Load() != 0.
 	sendLock mutex
+
+	// isSending is used to handle races between running a
+	// channel timer and stopping or resetting the timer.
+	// It is used only for channel timers (t.isChan == true).
+	// It is not used for tickers.
+	// The value is incremented when about to send a value on the channel,
+	// and decremented after sending the value.
+	// The stop/reset code uses this to detect whether it
+	// stopped the channel send.
+	//
+	// isSending is incremented only when t.mu is held.
+	// isSending is decremented only when t.sendLock is held.
+	// isSending is read only when both t.mu and t.sendLock are held.
+	isSending atomic.Int32
 }
 
 // init initializes a newly allocated timer t.
@@ -431,6 +446,15 @@ func (t *timer) stop() bool {
 		// Stop any future sends with stale values.
 		// See timer.unlockAndRun.
 		t.seq++
+
+		// If there is currently a send in progress,
+		// incrementing seq is going to prevent that
+		// send from actually happening. That means
+		// that we should return true: the timer was
+		// stopped, even though t.when may be zero.
+		if t.period == 0 && t.isSending.Load() > 0 {
+			pending = true
+		}
 	}
 	t.unlock()
 	if !async && t.isChan {
@@ -490,6 +514,7 @@ func (t *timer) modify(when, period int64, f func(arg any, seq uintptr, delay in
 		t.maybeRunAsync()
 	}
 	t.trace("modify")
+	oldPeriod := t.period
 	t.period = period
 	if f != nil {
 		t.f = f
@@ -525,6 +550,15 @@ func (t *timer) modify(when, period int64, f func(arg any, seq uintptr, delay in
 		// Stop any future sends with stale values.
 		// See timer.unlockAndRun.
 		t.seq++
+
+		// If there is currently a send in progress,
+		// incrementing seq is going to prevent that
+		// send from actually happening. That means
+		// that we should return true: the timer was
+		// stopped, even though t.when may be zero.
+		if oldPeriod == 0 && t.isSending.Load() > 0 {
+			pending = true
+		}
 	}
 	t.unlock()
 	if !async && t.isChan {
@@ -1013,6 +1047,15 @@ func (t *timer) unlockAndRun(now int64) {
 		}
 		t.updateHeap()
 	}
+
+	async := debug.asynctimerchan.Load() != 0
+	if !async && t.isChan && t.period == 0 {
+		// Tell Stop/Reset that we are sending a value.
+		if t.isSending.Add(1) < 0 {
+			throw("too many concurrent timer firings")
+		}
+	}
+
 	t.unlock()
 
 	if raceenabled {
@@ -1028,7 +1071,6 @@ func (t *timer) unlockAndRun(now int64) {
 		ts.unlock()
 	}
 
-	async := debug.asynctimerchan.Load() != 0
 	if !async && t.isChan {
 		// For a timer channel, we want to make sure that no stale sends
 		// happen after a t.stop or t.modify, but we cannot hold t.mu
@@ -1044,7 +1086,21 @@ func (t *timer) unlockAndRun(now int64) {
 		// and double-check that t.seq is still the seq value we saw above.
 		// If not, the timer has been updated and we should skip the send.
 		// We skip the send by reassigning f to a no-op function.
+		//
+		// The isSending field tells t.stop or t.modify that we have
+		// started to send the value. That lets them correctly return
+		// true meaning that no value was sent.
 		lock(&t.sendLock)
+
+		if t.period == 0 {
+			// We are committed to possibly sending a value
+			// based on seq, so no need to keep telling
+			// stop/modify that we are sending.
+			if t.isSending.Add(-1) < 0 {
+				throw("mismatched isSending updates")
+			}
+		}
+
 		if t.seq != seq {
 			f = func(any, uintptr, int64) {}
 		}
diff --git a/src/runtime/traceruntime.go b/src/runtime/traceruntime.go
index 195b3e1c37f984..7c4cb5502377c0 100644
--- a/src/runtime/traceruntime.go
+++ b/src/runtime/traceruntime.go
@@ -99,24 +99,26 @@ const (
 	traceBlockDebugCall
 	traceBlockUntilGCEnds
 	traceBlockSleep
+	traceBlockGCWeakToStrongWait
 )
 
 var traceBlockReasonStrings = [...]string{
-	traceBlockGeneric:         "unspecified",
-	traceBlockForever:         "forever",
-	traceBlockNet:             "network",
-	traceBlockSelect:          "select",
-	traceBlockCondWait:        "sync.(*Cond).Wait",
-	traceBlockSync:            "sync",
-	traceBlockChanSend:        "chan send",
-	traceBlockChanRecv:        "chan receive",
-	traceBlockGCMarkAssist:    "GC mark assist wait for work",
-	traceBlockGCSweep:         "GC background sweeper wait",
-	traceBlockSystemGoroutine: "system goroutine wait",
-	traceBlockPreempted:       "preempted",
-	traceBlockDebugCall:       "wait for debug call",
-	traceBlockUntilGCEnds:     "wait until GC ends",
-	traceBlockSleep:           "sleep",
+	traceBlockGeneric:            "unspecified",
+	traceBlockForever:            "forever",
+	traceBlockNet:                "network",
+	traceBlockSelect:             "select",
+	traceBlockCondWait:           "sync.(*Cond).Wait",
+	traceBlockSync:               "sync",
+	traceBlockChanSend:           "chan send",
+	traceBlockChanRecv:           "chan receive",
+	traceBlockGCMarkAssist:       "GC mark assist wait for work",
+	traceBlockGCSweep:            "GC background sweeper wait",
+	traceBlockSystemGoroutine:    "system goroutine wait",
+	traceBlockPreempted:          "preempted",
+	traceBlockDebugCall:          "wait for debug call",
+	traceBlockUntilGCEnds:        "wait until GC ends",
+	traceBlockSleep:              "sleep",
+	traceBlockGCWeakToStrongWait: "GC weak to strong wait",
 }
 
 // traceGoStopReason is an enumeration of reasons a goroutine might yield.
diff --git a/src/syscall/dll_windows.go b/src/syscall/dll_windows.go
index 81134cb0bd27ff..a7873e6ad8c93e 100644
--- a/src/syscall/dll_windows.go
+++ b/src/syscall/dll_windows.go
@@ -42,6 +42,7 @@ func Syscall15(trap, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a
 // Deprecated: Use [SyscallN] instead.
 func Syscall18(trap, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18 uintptr) (r1, r2 uintptr, err Errno)
 
+//go:noescape
 func SyscallN(trap uintptr, args ...uintptr) (r1, r2 uintptr, err Errno)
 func loadlibrary(filename *uint16) (handle uintptr, err Errno)
 func loadsystemlibrary(filename *uint16) (handle uintptr, err Errno)
diff --git a/src/syscall/exec_bsd.go b/src/syscall/exec_bsd.go
index 149cc2f11c128c..bbdab46de48c03 100644
--- a/src/syscall/exec_bsd.go
+++ b/src/syscall/exec_bsd.go
@@ -293,3 +293,8 @@ childerror:
 		RawSyscall(SYS_EXIT, 253, 0, 0)
 	}
 }
+
+// forkAndExecFailureCleanup cleans up after an exec failure.
+func forkAndExecFailureCleanup(attr *ProcAttr, sys *SysProcAttr) {
+	// Nothing to do.
+}
diff --git a/src/syscall/exec_freebsd.go b/src/syscall/exec_freebsd.go
index 3226cb88cd999a..686fd23bef435d 100644
--- a/src/syscall/exec_freebsd.go
+++ b/src/syscall/exec_freebsd.go
@@ -317,3 +317,8 @@ childerror:
 		RawSyscall(SYS_EXIT, 253, 0, 0)
 	}
 }
+
+// forkAndExecFailureCleanup cleans up after an exec failure.
+func forkAndExecFailureCleanup(attr *ProcAttr, sys *SysProcAttr) {
+	// Nothing to do.
+}
diff --git a/src/syscall/exec_libc.go b/src/syscall/exec_libc.go
index 768e8c131c1323..0e886508737d1e 100644
--- a/src/syscall/exec_libc.go
+++ b/src/syscall/exec_libc.go
@@ -314,6 +314,11 @@ childerror:
 	}
 }
 
+// forkAndExecFailureCleanup cleans up after an exec failure.
+func forkAndExecFailureCleanup(attr *ProcAttr, sys *SysProcAttr) {
+	// Nothing to do.
+}
+
 func ioctlPtr(fd, req uintptr, arg unsafe.Pointer) (err Errno) {
 	return ioctl(fd, req, uintptr(arg))
 }
diff --git a/src/syscall/exec_libc2.go b/src/syscall/exec_libc2.go
index 7a6750084486cf..a0579627a300bf 100644
--- a/src/syscall/exec_libc2.go
+++ b/src/syscall/exec_libc2.go
@@ -289,3 +289,8 @@ childerror:
 		rawSyscall(abi.FuncPCABI0(libc_exit_trampoline), 253, 0, 0)
 	}
 }
+
+// forkAndExecFailureCleanup cleans up after an exec failure.
+func forkAndExecFailureCleanup(attr *ProcAttr, sys *SysProcAttr) {
+	// Nothing to do.
+}
diff --git a/src/syscall/exec_linux.go b/src/syscall/exec_linux.go
index e4b9ce1bf47da3..dfd9a8368a9e50 100644
--- a/src/syscall/exec_linux.go
+++ b/src/syscall/exec_linux.go
@@ -7,6 +7,7 @@
 package syscall
 
 import (
+	errpkg "errors"
 	"internal/itoa"
 	"runtime"
 	"unsafe"
@@ -328,6 +329,7 @@ func forkAndExecInChild1(argv0 *byte, argv, envv []*byte, chroot, dir *byte, att
 	if clone3 != nil {
 		pid, err1 = rawVforkSyscall(_SYS_clone3, uintptr(unsafe.Pointer(clone3)), unsafe.Sizeof(*clone3), 0)
 	} else {
+		// N.B. Keep in sync with doCheckClonePidfd.
 		flags |= uintptr(SIGCHLD)
 		if runtime.GOARCH == "s390x" {
 			// On Linux/s390, the first two arguments of clone(2) are swapped.
@@ -735,3 +737,90 @@ func writeUidGidMappings(pid int, sys *SysProcAttr) error {
 
 	return nil
 }
+
+// forkAndExecFailureCleanup cleans up after an exec failure.
+func forkAndExecFailureCleanup(attr *ProcAttr, sys *SysProcAttr) {
+	if sys.PidFD != nil && *sys.PidFD != -1 {
+		Close(*sys.PidFD)
+		*sys.PidFD = -1
+	}
+}
+
+// checkClonePidfd verifies that clone(CLONE_PIDFD) works by actually doing a
+// clone.
+//
+//go:linkname os_checkClonePidfd os.checkClonePidfd
+func os_checkClonePidfd() error {
+	pidfd := int32(-1)
+	pid, errno := doCheckClonePidfd(&pidfd)
+	if errno != 0 {
+		return errno
+	}
+
+	if pidfd == -1 {
+		// Bad: CLONE_PIDFD failed to provide a pidfd. Reap the process
+		// before returning.
+
+		var err error
+		for {
+			var status WaitStatus
+			_, err = Wait4(int(pid), &status, 0, nil)
+			if err != EINTR {
+				break
+			}
+		}
+		if err != nil {
+			return err
+		}
+
+		return errpkg.New("clone(CLONE_PIDFD) failed to return pidfd")
+	}
+
+	// Good: CLONE_PIDFD provided a pidfd. Reap the process and close the
+	// pidfd.
+	defer Close(int(pidfd))
+
+	for {
+		const _P_PIDFD = 3
+		_, _, errno = Syscall6(SYS_WAITID, _P_PIDFD, uintptr(pidfd), 0, WEXITED, 0, 0)
+		if errno != EINTR {
+			break
+		}
+	}
+	if errno != 0 {
+		return errno
+	}
+
+	return nil
+}
+
+// doCheckClonePidfd implements the actual clone call of os_checkClonePidfd and
+// child execution. This is a separate function so we can separate the child's
+// and parent's stack frames if we're using vfork.
+//
+// This is go:noinline because the point is to keep the stack frames of this
+// and os_checkClonePidfd separate.
+//
+//go:noinline
+func doCheckClonePidfd(pidfd *int32) (pid uintptr, errno Errno) {
+	flags := uintptr(CLONE_VFORK|CLONE_VM|CLONE_PIDFD|SIGCHLD)
+	if runtime.GOARCH == "s390x" {
+		// On Linux/s390, the first two arguments of clone(2) are swapped.
+		pid, errno = rawVforkSyscall(SYS_CLONE, 0, flags, uintptr(unsafe.Pointer(pidfd)))
+	} else {
+		pid, errno = rawVforkSyscall(SYS_CLONE, flags, 0, uintptr(unsafe.Pointer(pidfd)))
+	}
+	if errno != 0 || pid != 0 {
+		// If we're in the parent, we must return immediately
+		// so we're not in the same stack frame as the child.
+		// This can at most use the return PC, which the child
+		// will not modify, and the results of
+		// rawVforkSyscall, which must have been written after
+		// the child was replaced.
+		return
+	}
+
+	for {
+		RawSyscall(SYS_EXIT_GROUP, 0, 0, 0)
+	}
+}
diff --git a/src/syscall/exec_unix.go b/src/syscall/exec_unix.go
index 1b90aa7e72e0ed..4747fa075834af 100644
--- a/src/syscall/exec_unix.go
+++ b/src/syscall/exec_unix.go
@@ -237,6 +237,10 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 		for err1 == EINTR {
 			_, err1 = Wait4(pid, &wstatus, 0, nil)
 		}
+
+		// OS-specific cleanup on failure.
+		forkAndExecFailureCleanup(attr, sys)
+
 		return 0, err
 	}
 
diff --git a/src/syscall/syscall_windows_test.go b/src/syscall/syscall_windows_test.go
index f67e8991591601..a6c6eff31f0c45 100644
--- a/src/syscall/syscall_windows_test.go
+++ b/src/syscall/syscall_windows_test.go
@@ -213,6 +213,51 @@ func TestGetStartupInfo(t *testing.T) {
 	}
 }
 
+func TestSyscallAllocations(t *testing.T) {
+	testenv.SkipIfOptimizationOff(t)
+
+	// Test that syscall.SyscallN arguments do not escape.
+	// The function used (in this case GetVersion) doesn't matter
+	// as long as it is always available and doesn't panic.
+	h, err := syscall.LoadLibrary("kernel32.dll")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer syscall.FreeLibrary(h)
+	proc, err := syscall.GetProcAddress(h, "GetVersion")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testAllocs := func(t *testing.T, name string, fn func() error) {
+		t.Run(name, func(t *testing.T) {
+			n := int(testing.AllocsPerRun(10, func() {
+				if err := fn(); err != nil {
+					t.Fatalf("%s: %v", name, err)
+				}
+			}))
+			if n > 0 {
+				t.Errorf("allocs = %d, want 0", n)
+			}
+		})
+	}
+
+	testAllocs(t, "SyscallN", func() error {
+		r0, _, e1 := syscall.SyscallN(proc, 0, 0, 0)
+		if r0 == 0 {
+			return syscall.Errno(e1)
+		}
+		return nil
+	})
+	testAllocs(t, "Syscall", func() error {
+		r0, _, e1 := syscall.Syscall(proc, 3, 0, 0, 0)
+		if r0 == 0 {
+			return syscall.Errno(e1)
+		}
+		return nil
+	})
+}
+
 func FuzzUTF16FromString(f *testing.F) {
 	f.Add("hi")           // ASCII
 	f.Add("â")            // latin1
diff --git a/src/time/sleep_test.go b/src/time/sleep_test.go
index 29f56ef7520baa..285a2e748c4af7 100644
--- a/src/time/sleep_test.go
+++ b/src/time/sleep_test.go
@@ -785,6 +785,119 @@ func TestAdjustTimers(t *testing.T) {
 	}
 }
 
+func TestStopResult(t *testing.T) {
+	testStopResetResult(t, true)
+}
+
+func TestResetResult(t *testing.T) {
+	testStopResetResult(t, false)
+}
+
+// Test that when racing between running a timer and stopping a timer Stop
+// consistently indicates whether a value can be read from the channel.
+// Issue #69312.
+func testStopResetResult(t *testing.T, testStop bool) {
+	for _, name := range []string{"0", "1", "2"} {
+		t.Run("asynctimerchan="+name, func(t *testing.T) {
+			testStopResetResultGODEBUG(t, testStop, name)
+		})
+	}
+}
+
+func testStopResetResultGODEBUG(t *testing.T, testStop bool, godebug string) {
+	t.Setenv("GODEBUG", "asynctimerchan="+godebug)
+
+	stopOrReset := func(timer *Timer) bool {
+		if testStop {
+			return timer.Stop()
+		} else {
+			return timer.Reset(1 * Hour)
+		}
+	}
+
+	start := make(chan struct{})
+	var wg sync.WaitGroup
+	const N = 1000
+	wg.Add(N)
+	for range N {
+		go func() {
+			defer wg.Done()
+			<-start
+			for j := 0; j < 100; j++ {
+				timer1 := NewTimer(1 * Millisecond)
+				timer2 := NewTimer(1 * Millisecond)
+				select {
+				case <-timer1.C:
+					if !stopOrReset(timer2) {
+						// The test fails if this
+						// channel read times out.
+						<-timer2.C
+					}
+				case <-timer2.C:
+					if !stopOrReset(timer1) {
+						// The test fails if this
+						// channel read times out.
+						<-timer1.C
+					}
+				}
+			}
+		}()
+	}
+	close(start)
+	wg.Wait()
+}
+
+// Test having a large number of goroutines wake up a ticker simultaneously.
+// This used to trigger a crash when run under x/tools/cmd/stress.
+func TestMultiWakeupTicker(t *testing.T) {
+	if testing.Short() {
+		t.Skip("-short")
+	}
+
+	goroutines := runtime.GOMAXPROCS(0)
+	timer := NewTicker(Microsecond)
+	var wg sync.WaitGroup
+	wg.Add(goroutines)
+	for range goroutines {
+		go func() {
+			defer wg.Done()
+			for range 100000 {
+				select {
+				case <-timer.C:
+				case <-After(Millisecond):
+				}
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+// Test having a large number of goroutines wake up a timer simultaneously.
+// This used to trigger a crash when run under x/tools/cmd/stress.
+func TestMultiWakeupTimer(t *testing.T) {
+	if testing.Short() {
+		t.Skip("-short")
+	}
+
+	goroutines := runtime.GOMAXPROCS(0)
+	timer := NewTimer(Nanosecond)
+	var wg sync.WaitGroup
+	wg.Add(goroutines)
+	for range goroutines {
+		go func() {
+			defer wg.Done()
+			for range 10000 {
+				select {
+				case <-timer.C:
+				default:
+				}
+				timer.Reset(Nanosecond)
+			}
+		}()
+	}
+	wg.Wait()
+}
+
 // Benchmark timer latency when the thread that creates the timer is busy with
 // other work and the timers must be serviced by other threads.
 // https://golang.org/issue/38860
diff --git a/src/time/time_test.go b/src/time/time_test.go
index 70eb61478480e0..c12b9117d0f5c1 100644
--- a/src/time/time_test.go
+++ b/src/time/time_test.go
@@ -14,6 +14,7 @@ import (
 	"math/rand"
 	"os"
 	"runtime"
+	"slices"
 	"strings"
 	"sync"
 	"testing"
@@ -1084,10 +1085,15 @@ func TestLoadFixed(t *testing.T) {
 	// So GMT+1 corresponds to -3600 in the Go zone, not +3600.
 	name, offset := Now().In(loc).Zone()
 	// The zone abbreviation is "-01" since tzdata-2016g, and "GMT+1"
-	// on earlier versions; we accept both. (Issue #17276).
-	if !(name == "GMT+1" || name == "-01") || offset != -1*60*60 {
-		t.Errorf("Now().In(loc).Zone() = %q, %d, want %q or %q, %d",
-			name, offset, "GMT+1", "-01", -1*60*60)
+	// on earlier versions; we accept both. (Issue 17276.)
+	wantName := []string{"GMT+1", "-01"}
+	// The zone abbreviation may be "+01" on OpenBSD. (Issue 69840.)
+	if runtime.GOOS == "openbsd" {
+		wantName = append(wantName, "+01")
+	}
+	if !slices.Contains(wantName, name) || offset != -1*60*60 {
+		t.Errorf("Now().In(loc).Zone() = %q, %d, want %q (one of), %d",
+			name, offset, wantName, -1*60*60)
 	}
 }
 
diff --git a/src/unique/clone_test.go b/src/unique/clone_test.go
index 69a9a540c07fa0..b0ba5b312e1466 100644
--- a/src/unique/clone_test.go
+++ b/src/unique/clone_test.go
@@ -27,7 +27,7 @@ func cSeq(stringOffsets ...uintptr) cloneSeq {
 
 func testCloneSeq[T any](t *testing.T, want cloneSeq) {
 	typName := reflect.TypeFor[T]().Name()
-	typ := abi.TypeOf(*new(T))
+	typ := abi.TypeFor[T]()
 	t.Run(typName, func(t *testing.T) {
 		got := makeCloneSeq(typ)
 		if !reflect.DeepEqual(got, want) {
diff --git a/src/unique/handle.go b/src/unique/handle.go
index 0842ae3185f2cc..abc620f60fe14e 100644
--- a/src/unique/handle.go
+++ b/src/unique/handle.go
@@ -31,7 +31,7 @@ func (h Handle[T]) Value() T {
 // are equal if and only if the values used to produce them are equal.
 func Make[T comparable](value T) Handle[T] {
 	// Find the map for type T.
-	typ := abi.TypeOf(value)
+	typ := abi.TypeFor[T]()
 	ma, ok := uniqueMaps.Load(typ)
 	if !ok {
 		// This is a good time to initialize cleanup, since we must go through
@@ -50,13 +50,13 @@ func Make[T comparable](value T) Handle[T] {
 		toInsert     *T // Keep this around to keep it alive.
 		toInsertWeak weak.Pointer[T]
 	)
-	newValue := func() weak.Pointer[T] {
+	newValue := func() (T, weak.Pointer[T]) {
 		if toInsert == nil {
 			toInsert = new(T)
 			*toInsert = clone(value, &m.cloneSeq)
 			toInsertWeak = weak.Make(toInsert)
 		}
-		return toInsertWeak
+		return *toInsert, toInsertWeak
 	}
 	var ptr *T
 	for {
@@ -64,7 +64,8 @@ func Make[T comparable](value T) Handle[T] {
 		wp, ok := m.Load(value)
 		if !ok {
 			// Try to insert a new value into the map.
-			wp, _ = m.LoadOrStore(value, newValue())
+			k, v := newValue()
+			wp, _ = m.LoadOrStore(k, v)
 		}
 		// Now that we're sure there's a value in the map, let's
 		// try to get the pointer we need out of it.
diff --git a/src/unique/handle_test.go b/src/unique/handle_test.go
index dffe10ac728189..dd4b01ef79900b 100644
--- a/src/unique/handle_test.go
+++ b/src/unique/handle_test.go
@@ -9,7 +9,10 @@ import (
 	"internal/abi"
 	"reflect"
 	"runtime"
+	"strings"
 	"testing"
+	"time"
+	"unsafe"
 )
 
 // Set up special types. Because the internal maps are sharded by type,
@@ -41,6 +44,7 @@ func TestHandle(t *testing.T) {
 		s: [2]testStringStruct{testStringStruct{"y"}, testStringStruct{"z"}},
 	})
 	testHandle[testStruct](t, testStruct{0.5, "184"})
+	testHandle[testEface](t, testEface("hello"))
 }
 
 func testHandle[T comparable](t *testing.T, value T) {
@@ -93,7 +97,7 @@ func drainMaps(t *testing.T) {
 
 func checkMapsFor[T comparable](t *testing.T, value T) {
 	// Manually load the value out of the map.
-	typ := abi.TypeOf(value)
+	typ := abi.TypeFor[T]()
 	a, ok := uniqueMaps.Load(typ)
 	if !ok {
 		return
@@ -109,3 +113,22 @@ func checkMapsFor[T comparable](t *testing.T, value T) {
 	}
 	t.Errorf("failed to drain internal maps of %v", value)
 }
+
+func TestMakeClonesStrings(t *testing.T) {
+	s := strings.Clone("abcdefghijklmnopqrstuvwxyz") // N.B. Must be big enough to not be tiny-allocated.
+	ran := make(chan bool)
+	runtime.SetFinalizer(unsafe.StringData(s), func(_ *byte) {
+		ran <- true
+	})
+	h := Make(s)
+
+	// Clean up s (hopefully) and run the finalizer.
+	runtime.GC()
+
+	select {
+	case <-time.After(1 * time.Second):
+		t.Fatal("string was improperly retained")
+	case <-ran:
+	}
+	runtime.KeepAlive(h)
+}
diff --git a/test/fixedbugs/issue14636.go b/test/fixedbugs/issue14636.go
index c8e751fb613c2e..a866c9a9e30e8e 100644
--- a/test/fixedbugs/issue14636.go
+++ b/test/fixedbugs/issue14636.go
@@ -12,22 +12,29 @@ import (
 	"bytes"
 	"log"
 	"os/exec"
+	"runtime"
 	"strings"
 )
 
 func main() {
-	checkLinkOutput("", "-B argument must start with 0x")
+	// The cannot open file error indicates that the parsing of -B flag
+	// succeeded and it failed at a later step.
 	checkLinkOutput("0", "-B argument must start with 0x")
-	checkLinkOutput("0x", "usage")
+	checkLinkOutput("0x", "cannot open file nonexistent.o")
 	checkLinkOutput("0x0", "-B argument must have even number of digits")
-	checkLinkOutput("0x00", "usage")
+	checkLinkOutput("0x00", "cannot open file nonexistent.o")
 	checkLinkOutput("0xYZ", "-B argument contains invalid hex digit")
-	checkLinkOutput("0x"+strings.Repeat("00", 32), "usage")
-	checkLinkOutput("0x"+strings.Repeat("00", 33), "-B option too long (max 32 digits)")
+
+	maxLen := 32
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		maxLen = 16
+	}
+	checkLinkOutput("0x"+strings.Repeat("00", maxLen), "cannot open file nonexistent.o")
+	checkLinkOutput("0x"+strings.Repeat("00", maxLen+1), "-B option too long")
 }
 
 func checkLinkOutput(buildid string, message string) {
-	cmd := exec.Command("go", "tool", "link", "-B", buildid)
+	cmd := exec.Command("go", "tool", "link", "-B", buildid, "nonexistent.o")
 	out, err := cmd.CombinedOutput()
 	if err == nil {
 		log.Fatalf("expected cmd/link to fail")
@@ -39,6 +46,6 @@ func checkLinkOutput(buildid string, message string) {
 	}
 
 	if !strings.Contains(firstLine, message) {
-		log.Fatalf("cmd/link output did not include expected message %q: %s", message, firstLine)
+		log.Fatalf("%s: cmd/link output did not include expected message %q: %s", buildid, message, firstLine)
 	}
 }
diff --git a/test/fixedbugs/issue63489a.go b/test/fixedbugs/issue63489a.go
index b88120f2c045ef..2b46814f9566de 100644
--- a/test/fixedbugs/issue63489a.go
+++ b/test/fixedbugs/issue63489a.go
@@ -1,16 +1,20 @@
-// errorcheck -lang=go1.21
+// errorcheck -lang=go1.22
 
 // Copyright 2023 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.4
+// This file has been changed from its original version as
+// //go:build file versions below 1.21 set the language version to 1.21.
+// The original tested a -lang version of 1.21 with a file version of
+// go1.4 while this new version tests a -lang version of go1.22
+// with a file version of go1.21.
 
-package p
-
-const c = 0o123 // ERROR "file declares //go:build go1.4"
+//go:build go1.21
 
-// ERROR "file declares //go:build go1.4"
+package p
 
-//line issue63489a.go:13:1
-const d = 0o124
+func f() {
+	for _ = range 10 { // ERROR "file declares //go:build go1.21"
+	}
+}
diff --git a/test/fixedbugs/issue63489b.go b/test/fixedbugs/issue63489b.go
index 2ad590dfc33347..fd897dea97cb88 100644
--- a/test/fixedbugs/issue63489b.go
+++ b/test/fixedbugs/issue63489b.go
@@ -1,11 +1,20 @@
-// errorcheck -lang=go1.4
+// errorcheck -lang=go1.21
 
 // Copyright 2023 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.4
+// This file has been changed from its original version as
+// //go:build file versions below 1.21 set the language version to 1.21.
+// The original tested a -lang version of 1.4 with a file version of
+// go1.4 while this new version tests a -lang version of go1.1
+// with a file version of go1.21.
+
+//go:build go1.21
 
 package p
 
-const c = 0o123 // ERROR "file declares //go:build go1.4"
+func f() {
+	for _ = range 10 { // ERROR "file declares //go:build go1.21"
+	}
+}
diff --git a/test/fixedbugs/issue68580.go b/test/fixedbugs/issue68580.go
new file mode 100644
index 00000000000000..b60a7447aaa77b
--- /dev/null
+++ b/test/fixedbugs/issue68580.go
@@ -0,0 +1,15 @@
+// compile -goexperiment aliastypeparams
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type A[P any] = struct{ _ P }
+
+type N[P any] A[P]
+
+func f[P any](N[P]) {}
+
+var _ = f[int]
diff --git a/test/fixedbugs/issue69110.go b/test/fixedbugs/issue69110.go
new file mode 100644
index 00000000000000..71a4bcac31a16e
--- /dev/null
+++ b/test/fixedbugs/issue69110.go
@@ -0,0 +1,57 @@
+// run
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"maps"
+	_ "unsafe"
+)
+
+func main() {
+	for i := 0; i < 100; i++ {
+		f()
+	}
+}
+
+const NB = 4
+
+func f() {
+	// Make a map with NB buckets, at max capacity.
+	// 6.5 entries/bucket.
+	ne := NB * 13 / 2
+	m := map[int]int{}
+	for i := 0; i < ne; i++ {
+		m[i] = i
+	}
+
+	// delete/insert a lot, to hopefully get lots of overflow buckets
+	// and trigger a same-size grow.
+	ssg := false
+	for i := ne; i < ne+1000; i++ {
+		delete(m, i-ne)
+		m[i] = i
+		if sameSizeGrow(m) {
+			ssg = true
+			break
+		}
+	}
+	if !ssg {
+		return
+	}
+
+	// Insert 1 more entry, which would ordinarily trigger a growth.
+	// We can't grow while growing, so we instead go over our
+	// target capacity.
+	m[-1] = -1
+
+	// Cloning in this state will make a map with a destination bucket
+	// array twice the size of the source.
+	_ = maps.Clone(m)
+}
+
+//go:linkname sameSizeGrow runtime.sameSizeGrowForIssue69110Test
+func sameSizeGrow(m map[int]int) bool
diff --git a/test/fixedbugs/issue69434.go b/test/fixedbugs/issue69434.go
new file mode 100644
index 00000000000000..682046601960da
--- /dev/null
+++ b/test/fixedbugs/issue69434.go
@@ -0,0 +1,173 @@
+// run
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"iter"
+	"math/rand"
+	"os"
+	"strings"
+	"unicode"
+)
+
+// WordReader is the struct that implements io.Reader
+type WordReader struct {
+	scanner *bufio.Scanner
+}
+
+// NewWordReader creates a new WordReader from an io.Reader
+func NewWordReader(r io.Reader) *WordReader {
+	scanner := bufio.NewScanner(r)
+	scanner.Split(bufio.ScanWords)
+	return &WordReader{
+		scanner: scanner,
+	}
+}
+
+// Read reads data from the input stream and returns a single lowercase word at a time
+func (wr *WordReader) Read(p []byte) (n int, err error) {
+	if !wr.scanner.Scan() {
+		if err := wr.scanner.Err(); err != nil {
+			return 0, err
+		}
+		return 0, io.EOF
+	}
+	word := wr.scanner.Text()
+	cleanedWord := removeNonAlphabetic(word)
+	if len(cleanedWord) == 0 {
+		return wr.Read(p)
+	}
+	n = copy(p, []byte(cleanedWord))
+	return n, nil
+}
+
+// All returns an iterator allowing the caller to iterate over the WordReader using for/range.
+func (wr *WordReader) All() iter.Seq[string] {
+	word := make([]byte, 1024)
+	return func(yield func(string) bool) {
+		var err error
+		var n int
+		for n, err = wr.Read(word); err == nil; n, err = wr.Read(word) {
+			if !yield(string(word[:n])) {
+				return
+			}
+		}
+		if err != io.EOF {
+			fmt.Fprintf(os.Stderr, "error reading word: %v\n", err)
+		}
+	}
+}
+
+// removeNonAlphabetic removes non-alphabetic characters from a word using strings.Map
+func removeNonAlphabetic(word string) string {
+	return strings.Map(func(r rune) rune {
+		if unicode.IsLetter(r) {
+			return unicode.ToLower(r)
+		}
+		return -1
+	}, word)
+}
+
+// ProbabilisticSkipper determines if an item should be retained with probability 1/(1<<n)
+type ProbabilisticSkipper struct {
+	n       int
+	counter uint64
+	bitmask uint64
+}
+
+// NewProbabilisticSkipper initializes the ProbabilisticSkipper
+func NewProbabilisticSkipper(n int) *ProbabilisticSkipper {
+	pr := &ProbabilisticSkipper{n: n}
+	pr.refreshCounter()
+	return pr
+}
+
+// check panics if pr.n is not the expected value
+func (pr *ProbabilisticSkipper) check(n int) {
+	if pr.n != n {
+		panic(fmt.Sprintf("check: pr.n != n  %d != %d", pr.n, n))
+	}
+}
+
+// refreshCounter refreshes the counter with a new random value
+func (pr *ProbabilisticSkipper) refreshCounter() {
+	if pr.n == 0 {
+		pr.bitmask = ^uint64(0) // All bits set to 1
+	} else {
+		pr.bitmask = rand.Uint64()
+		for i := 0; i < pr.n-1; i++ {
+			pr.bitmask &= rand.Uint64()
+		}
+	}
+	pr.counter = 64
+}
+
+// ShouldSkip returns true with probability 1/(1<<n)
+func (pr *ProbabilisticSkipper) ShouldSkip() bool {
+	remove := pr.bitmask&1 == 0
+	pr.bitmask >>= 1
+	pr.counter--
+	if pr.counter == 0 {
+		pr.refreshCounter()
+	}
+	return remove
+}
+
+// EstimateUniqueWordsIter estimates the number of unique words using a probabilistic counting method
+func EstimateUniqueWordsIter(reader io.Reader, memorySize int) int {
+	wordReader := NewWordReader(reader)
+	words := make(map[string]struct{}, memorySize)
+
+	rounds := 0
+	roundRemover := NewProbabilisticSkipper(1)
+	wordSkipper := NewProbabilisticSkipper(rounds)
+	wordSkipper.check(rounds)
+
+	for word := range wordReader.All() {
+		wordSkipper.check(rounds)
+		if wordSkipper.ShouldSkip() {
+			delete(words, word)
+		} else {
+			words[word] = struct{}{}
+
+			if len(words) >= memorySize {
+				rounds++
+
+				wordSkipper = NewProbabilisticSkipper(rounds)
+				for w := range words {
+					if roundRemover.ShouldSkip() {
+						delete(words, w)
+					}
+				}
+			}
+		}
+		wordSkipper.check(rounds)
+	}
+
+	if len(words) == 0 {
+		return 0
+	}
+
+	invProbability := 1 << rounds
+	estimatedUniqueWords := len(words) * invProbability
+	return estimatedUniqueWords
+}
+
+func main() {
+	input := "Hello, world! This is a test. Hello, world, hello!"
+	expectedUniqueWords := 6 // "hello", "world", "this", "is", "a", "test" (but "hello" and "world" are repeated)
+	memorySize := 6
+
+	reader := strings.NewReader(input)
+	estimatedUniqueWords := EstimateUniqueWordsIter(reader, memorySize)
+	if estimatedUniqueWords != expectedUniqueWords {
+		// ...
+	}
+}
diff --git a/test/fixedbugs/issue69507.go b/test/fixedbugs/issue69507.go
new file mode 100644
index 00000000000000..fc300c848ee62f
--- /dev/null
+++ b/test/fixedbugs/issue69507.go
@@ -0,0 +1,133 @@
+// run
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+	err := run()
+	if err != nil {
+		panic(err)
+	}
+}
+
+func run() error {
+	methods := "AB"
+
+	type node struct {
+		tag     string
+		choices []string
+	}
+	all := []node{
+		{"000", permutations(methods)},
+	}
+
+	next := 1
+	for len(all) > 0 {
+		cur := all[0]
+		k := copy(all, all[1:])
+		all = all[:k]
+
+		if len(cur.choices) == 1 {
+			continue
+		}
+
+		var bestM map[byte][]string
+		bMax := len(cur.choices) + 1
+		bMin := -1
+		for sel := range selections(methods) {
+			m := make(map[byte][]string)
+			for _, order := range cur.choices {
+				x := findFirstMatch(order, sel)
+				m[x] = append(m[x], order)
+			}
+
+			min := len(cur.choices) + 1
+			max := -1
+			for _, v := range m {
+				if len(v) < min {
+					min = len(v)
+				}
+				if len(v) > max {
+					max = len(v)
+				}
+			}
+			if max < bMax || (max == bMax && min > bMin) {
+				bestM = m
+				bMin = min
+				bMax = max
+			}
+		}
+
+		if bMax == len(cur.choices) {
+			continue
+		}
+
+		cc := Keys(bestM)
+		for c := range cc {
+			choices := bestM[c]
+			next++
+
+			switch c {
+			case 'A':
+			case 'B':
+			default:
+				panic("unexpected selector type " + string(c))
+			}
+			all = append(all, node{"", choices})
+		}
+	}
+	return nil
+}
+
+func permutations(s string) []string {
+	if len(s) <= 1 {
+		return []string{s}
+	}
+
+	var result []string
+	for i, char := range s {
+		rest := s[:i] + s[i+1:]
+		for _, perm := range permutations(rest) {
+			result = append(result, string(char)+perm)
+		}
+	}
+	return result
+}
+
+type Seq[V any] func(yield func(V) bool)
+
+func selections(s string) Seq[string] {
+	return func(yield func(string) bool) {
+		for bits := 1; bits < 1<<len(s); bits++ {
+			var choice string
+			for j, char := range s {
+				if bits&(1<<j) != 0 {
+					choice += string(char)
+				}
+			}
+			if !yield(choice) {
+				break
+			}
+		}
+	}
+}
+
+func findFirstMatch(order, sel string) byte {
+	for _, c := range order {
+		return byte(c)
+	}
+	return 0
+}
+
+func Keys[Map ~map[K]V, K comparable, V any](m Map) Seq[K] {
+	return func(yield func(K) bool) {
+		for k := range m {
+			if !yield(k) {
+				return
+			}
+		}
+	}
+}