Fix data race on CpuProfiler::running_

BUG=v8:3613
R=yangguo@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/632313002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24439 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/cpu-profiler.cc

@@ -20,17 +20,16 @@ namespace internal {
 static const int kProfilerStackSize = 64 * KB;
 
 
-ProfilerEventsProcessor::ProfilerEventsProcessor(
-    ProfileGenerator* generator,
-    Sampler* sampler,
-    base::TimeDelta period)
+ProfilerEventsProcessor::ProfilerEventsProcessor(ProfileGenerator* generator,
+                                                 Sampler* sampler,
+                                                 base::TimeDelta period)
     : Thread(Thread::Options("v8:ProfEvntProc", kProfilerStackSize)),
       generator_(generator),
       sampler_(sampler),
-      running_(true),
+      running_(1),
       period_(period),
-      last_code_event_id_(0), last_processed_code_event_id_(0) {
-}
+      last_code_event_id_(0),
+      last_processed_code_event_id_(0) {}
 
 
 void ProfilerEventsProcessor::Enqueue(const CodeEventsContainer& event) {
@@ -55,8 +54,7 @@ void ProfilerEventsProcessor::AddCurrentStack(Isolate* isolate) {
 
 
 void ProfilerEventsProcessor::StopSynchronously() {
-  if (!running_) return;
-  running_ = false;
+  if (!base::NoBarrier_AtomicExchange(&running_, 0)) return;
   Join();
 }
 
@@ -107,7 +105,7 @@ ProfilerEventsProcessor::SampleProcessingResult
 
 
 void ProfilerEventsProcessor::Run() {
-  while (running_) {
+  while (!!base::NoBarrier_Load(&running_)) {
     base::ElapsedTimer timer;
     timer.Start();
     // Keep processing existing events until we need to do next sample.

src/cpu-profiler.h

@@ -132,7 +132,7 @@ class ProfilerEventsProcessor : public base::Thread {
   // Thread control.
   virtual void Run();
   void StopSynchronously();
-  INLINE(bool running()) { return running_; }
+  INLINE(bool running()) { return !!base::NoBarrier_Load(&running_); }
   void Enqueue(const CodeEventsContainer& event);
 
   // Puts current stack into tick sample events buffer.
@@ -163,7 +163,7 @@ class ProfilerEventsProcessor : public base::Thread {
 
   ProfileGenerator* generator_;
   Sampler* sampler_;
-  bool running_;
+  base::Atomic32 running_;
   // Sampling period in microseconds.
   const base::TimeDelta period_;
   UnboundQueue<CodeEventsContainer> events_buffer_;