From f9f2233ef9b768606dedc3acde01dc175fc8dfff Mon Sep 17 00:00:00 2001
From: Bart Janssens <bart@bartjanssens.org>
Date: Mon, 26 Feb 2018 08:05:48 +0100
Subject: [PATCH] Simplify wait_nb_available in WindowIO

---
 src/window-io.jl | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/src/window-io.jl b/src/window-io.jl
index d40e61e14..930e5af59 100644
--- a/src/window-io.jl
+++ b/src/window-io.jl
@@ -29,7 +29,6 @@ mutable struct WindowIO <: IO
     header::BufferHeader
     remote_header::BufferHeader
     header_win::Win
-    header_cwin::CWin
     is_open::Bool
     # Current read position
     ptr::WinCountT
@@ -56,7 +55,6 @@ mutable struct WindowIO <: IO
             header,
             remote_header,
             header_win,
-            CWin(header_win),
             true,
             0,
             Condition(),
@@ -92,23 +90,23 @@ function has_data_available(w::WindowIO)
         return false
     end
 
-    if w.header.count > w.ptr && w.header.needed_length == w.header.length # fast check without window sync
-        return true
-    end
-
-    # Check if we need to grow the buffer
-    MPI.Win_lock(MPI.LOCK_EXCLUSIVE, w.myrank, 0, w.header_win)
-    MPI.Win_sync(w.header_cwin) # CWin version doesn't allocate
-    if w.header.needed_length > w.header.length
+    MPI.Win_lock(MPI.LOCK_SHARED, w.myrank, 0, w.header_win)
+    have_data = w.header.count > w.ptr
+    need_grow = w.header.needed_length > w.header.length
+    MPI.Win_unlock(w.myrank, w.header_win)
+    
+    # Grow buffer if needed
+    if need_grow
         MPI.Win_detach(w.win, w.buffer)
         resize!(w.buffer, w.header.needed_length)
         MPI.Win_attach(w.win, w.buffer)
+        MPI.Win_lock(MPI.LOCK_EXCLUSIVE, w.myrank, 0, w.header_win)
         w.header.address = MPI.Get_address(w.buffer)
         w.header.length = w.header.needed_length
+        MPI.Win_unlock(w.myrank, w.header_win)
     end
-    MPI.Win_unlock(w.myrank, w.header_win)
     
-    return w.header.count > w.ptr
+    return have_data
 end
 
 function Base.wait(w::WindowIO)
@@ -126,11 +124,8 @@ end
 
 # wait until the specified number of bytes is available or the stream is closed
 function wait_nb_available(w, nb)
-    nb_found = wait_nb_available(w)
+    nb_found = 0
     while nb_found < nb && w.is_open
-        MPI.Win_lock(MPI.LOCK_SHARED, w.myrank, 0, w.header_win)
-        MPI.Win_sync(w.header_cwin) # sync every loop, to make sure we get updates
-        MPI.Win_unlock(w.myrank, w.header_win)
         nb_found = wait_nb_available(w)
     end
     return nb_found