From 0fbf4f02117fca1cf7f5ed84205d8504ce174f6f Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Sat, 25 Jan 2020 15:22:12 +0100
Subject: [PATCH] [Support] Fix race in threading test, found by TSan

---
 unittests/Support/Threading.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/unittests/Support/Threading.cpp b/unittests/Support/Threading.cpp
index 21baa55ef44..183c9aa7d71 100644
--- a/unittests/Support/Threading.cpp
+++ b/unittests/Support/Threading.cpp
@@ -32,8 +32,10 @@ public:
     {
       std::lock_guard<std::mutex> Lock(M);
       Notified = true;
+      // Broadcast with the lock held, so it's safe to destroy the Notification
+      // after wait() returns.
+      CV.notify_all();
     }
-    CV.notify_all();
   }
 
   bool wait() {