[PATCH] D18811: Fix a race condition in support library ThreadPool

[Justin Lebar via llvm-commits]

jlebar added inline comments.

================
Comment at: lib/Support/ThreadPool.cpp:79
@@ -78,3 +70,3 @@
   CompletionCondition.wait(LockGuard,
                            [&] { return Tasks.empty() && !ActiveThreads; });
 }
----------------
joker.eph wrote:
> Would just reversing the check solve the race?
> 
> ```
>  [&] { return !ActiveThreads && Tasks.empty(); });
> ```
> 
> If not can you elaborate a little?
> 
The race is that we touch Tasks here while holding only CompletionLock, while another thread in asyncImpl may touch Tasks while holding only QueueLock.


http://reviews.llvm.org/D18811