Hold allocator lock while fetching 'used' count.

base/debug/activity_analyzer_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/activity_analyzer.h"
 
 #include <atomic>
 #include <memory>
 
 #include "base/bind.h"
@@ skipping 86 matching lines @@
 
   ~SimpleActivityThread() override {}
 
   void Run() override {
     GlobalActivityTracker::Get()
         ->GetOrCreateTrackerForCurrentThread()
         ->PushActivity(source_, activity_, data_);
 
     {
       AutoLock auto_lock(lock_);
-      ready_.store(true, std::memory_order_relaxed);
+      ready_.store(true, std::memory_order_release);
       while (!exit_.load(std::memory_order_relaxed))
         exit_condition_.Wait();
     }
 
     GlobalActivityTracker::Get()
         ->GetOrCreateTrackerForCurrentThread()
         ->PopActivity();
   }
 
   void Exit() {
     AutoLock auto_lock(lock_);
     exit_.store(true, std::memory_order_relaxed);
     exit_condition_.Signal();
   }
 
   void WaitReady() {
-    SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(ready_.load(std::memory_order_relaxed));
+    SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(ready_.load(std::memory_order_acquire));
   }
 
  private:
   const void* source_;
   Activity::Type activity_;
   ActivityData data_;
 
   std::atomic<bool> ready_;
   std::atomic<bool> exit_;
   Lock lock_;
@@ skipping 37 matching lines @@
   ThreadActivityAnalyzer* ta2 = analyzer.GetFirstAnalyzer();
   ASSERT_TRUE(ta2);
   EXPECT_FALSE(analyzer.GetNextAnalyzer());
   ThreadActivityAnalyzer::ThreadKey tk2 = ta2->GetThreadKey();
   EXPECT_EQ(ta2, analyzer.GetAnalyzerForThread(tk2));
   EXPECT_EQ(tk1, tk2);
 }
 
 }  // namespace debug
 }  // namespace base