[compiler-rt] r303869 - [sanitizer] Pair atomic acquire with release in BlockingMutex::Unlock

[Alex Shlyapnikov via llvm-commits]

Author: alekseyshl
Date: Thu May 25 10:07:07 2017
New Revision: 303869

URL: http://llvm.org/viewvc/llvm-project?rev=303869&view=rev
Log:
[sanitizer] Pair atomic acquire with release in BlockingMutex::Unlock

Summary:
Dmitry, seeking your expertise. I believe, the proper way to implement
Lock/Unlock here would be to use acquire/release semantics. Am I missing
something?

Reviewers: dvyukov

Subscribers: llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D33521

Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc?rev=303869&r1=303868&r2=303869&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc Thu May 25 10:07:07 2017
@@ -549,7 +549,7 @@ void BlockingMutex::Lock() {
 
 void BlockingMutex::Unlock() {
   atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
-  u32 v = atomic_exchange(m, MtxUnlocked, memory_order_relaxed);
+  u32 v = atomic_exchange(m, MtxUnlocked, memory_order_release);
   CHECK_NE(v, MtxUnlocked);
   if (v == MtxSleeping) {
 #if SANITIZER_FREEBSD