[llvm-branch-commits] [clang-tools-extra] f23ee06 - [clangd] Fix race in Global CDB shutdown

[Tom Stellard via llvm-branch-commits]

Author: Sam McCall
Date: 2021-02-16T16:58:17-08:00
New Revision: f23ee06ec27e991f9f1fbb646f3a2288aeedee71

URL: https://github.com/llvm/llvm-project/commit/f23ee06ec27e991f9f1fbb646f3a2288aeedee71
DIFF: https://github.com/llvm/llvm-project/commit/f23ee06ec27e991f9f1fbb646f3a2288aeedee71.diff

LOG: [clangd] Fix race in Global CDB shutdown

I believe the atomic write can be reordered after the notify, and that
seems to be happening on mac m1: http://45.33.8.238/macm1/2654/step_8.txt
In practice maybe seq_cst is enough? But no reason not to lock here.

https://bugs.llvm.org/show_bug.cgi?id=48998
(cherry picked from commit 6ac3fd9706047304c52a678884122a3a6bc55432)

Added: 
    

Modified: 
    clang-tools-extra/clangd/GlobalCompilationDatabase.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
index 1a5379acfe7d..542d0c3e4dbc 100644
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
@@ -34,6 +34,7 @@
 #include <atomic>
 #include <chrono>
 #include <condition_variable>
+#include <mutex>
 #include <string>
 #include <tuple>
 #include <vector>
@@ -567,7 +568,10 @@ class DirectoryBasedGlobalCompilationDatabase::BroadcastThread {
   }
 
   ~BroadcastThread() {
-    ShouldStop.store(true, std::memory_order_release);
+    {
+      std::lock_guard<std::mutex> Lock(Mu);
+      ShouldStop.store(true, std::memory_order_release);
+    }
     CV.notify_all();
     Thread.join();
   }