Fix lxcfs cpuinfo

enterprise/server/cmd/executor/executor_linux.go

@@ -79,6 +79,12 @@ func setupCgroups() (string, error) {
 	}
 	log.Infof("Set up task cgroup at %s", taskCgroupPath)
 
+	// Enable the same controllers for the child cgroups that were enabled
+	// for the starting cgroup.
+	if err := cgroup.DelegateControllers(filepath.Join(cgroup.RootPath, startingCgroup)); err != nil {
+		return "", fmt.Errorf("inherit subtree control: %w", err)
+	}
+
 	taskCgroupRelpath := filepath.Join(startingCgroup, taskCgroupName)
 	return taskCgroupRelpath, nil
 }

enterprise/server/remote_execution/cgroup/cgroup.go

@@ -81,7 +81,7 @@ func Setup(ctx context.Context, path string, s *scpb.CgroupSettings, blockDevice
 	if len(m) == 0 {
 		return nil
 	}
-	enabledControllers, err := ParentEnabledControllers(path)
+	enabledControllers, err := EnabledControllers(path)
 	if err != nil {
 		return fmt.Errorf("read enabled controllers: %w", err)
 	}
@@ -99,10 +99,10 @@ func Setup(ctx context.Context, path string, s *scpb.CgroupSettings, blockDevice
 	return nil
 }
 
-// ParentEnabledControllers returns the cgroup controllers that are enabled for
-// the parent cgroup of a given cgroup.
-func ParentEnabledControllers(path string) (map[string]bool, error) {
-	b, err := os.ReadFile(filepath.Join(path, "..", "cgroup.subtree_control"))
+// EnabledControllers returns the controllers enabled for the cgroup at the
+// given absolute path.
+func EnabledControllers(path string) (map[string]bool, error) {
+	b, err := os.ReadFile(filepath.Join(path, "cgroup.controllers"))
 	if err != nil {
 		return nil, err
 	}
@@ -133,6 +133,20 @@ func WriteSubtreeControl(path string, settings map[string]bool) error {
 	return os.WriteFile(filepath.Join(path, "cgroup.subtree_control"), b, 0)
 }
 
+// DelegateControllers reads the currently enabled controllers for the given
+// cgroup absolute path and makes those controllers available to child cgroups
+// by writing to the "cgroup.subtree_control" file.
+func DelegateControllers(path string) error {
+	controllers, err := EnabledControllers(path)
+	if err != nil {
+		return fmt.Errorf("read enabled controllers for %q: %w", path, err)
+	}
+	if err := WriteSubtreeControl(path, controllers); err != nil {
+		return fmt.Errorf("write cgroup.subtree_control for %q: %w", path, err)
+	}
+	return nil
+}
+
 func settingsMap(s *scpb.CgroupSettings, blockDevice *block_io.Device) (map[string]string, error) {
 	m := map[string]string{}
 	if s == nil {

enterprise/server/remote_execution/containers/ociruntime/ociruntime.go

@@ -695,16 +695,10 @@ func (c *ociContainer) setupCgroup(ctx context.Context) error {
 	if err := os.MkdirAll(path, 0755); err != nil {
 		return fmt.Errorf("create cgroup: %w", err)
 	}
-	// Before setting up the container cgroup we need to enable subtree
-	// controllers on the parent cgroup. For now we inherit the enabled
-	// controllers from the parent of the parent.
-	parentPath := filepath.Dir(path)
-	controllers, err := cgroup.ParentEnabledControllers(parentPath)
-	if err != nil {
-		return fmt.Errorf("read enabled controllers for parent of %q: %w", parentPath, err)
-	}
-	if err := cgroup.WriteSubtreeControl(parentPath, controllers); err != nil {
-		return fmt.Errorf("write cgroup.subtree_control for %q: %w", parentPath, err)
+	// Propagate enabled controllers to the child cgroup before performing
+	// cgroup setup.
+	if err := cgroup.DelegateControllers(filepath.Dir(path)); err != nil {
+		return fmt.Errorf("delegate controllers: %w", err)
 	}
 	if err := cgroup.Setup(ctx, path, c.cgroupSettings, c.blockDevice); err != nil {
 		return fmt.Errorf("configure cgroup: %w", err)