Bug 698002. Change active_ to Atomic32. r=bgirard

This brings us closer to V8

--HG--
extra : rebase_source : 75685ef885ed1f8abb4ef7a6144d6581a2316941

tools/profiler/sps/platform-linux.cc

@@ -295,7 +295,7 @@ void Sampler::Start() {
   // Start a thread that sends SIGPROF signal to VM thread.
   // Sending the signal ourselves instead of relying on itimer provides
   // much better accuracy.
-  active_ = true;
+  SetActive(true);
   if (pthread_create(
           &data_->signal_sender_thread_, NULL, SenderEntry, data_) == 0) {
     data_->signal_sender_launched_ = true;
@@ -308,7 +308,7 @@ void Sampler::Start() {
 
 
 void Sampler::Stop() {
-  active_ = false;
+  SetActive(false);
 
   // Wait for signal sender termination (it will exit after setting
   // active_ to false).

tools/profiler/sps/platform.h

@@ -144,10 +144,12 @@ class Sampler {
   class PlatformData;
 
  private:
+  void SetActive(bool value) { NoBarrier_Store(&active_, value); }
+
   const int interval_;
   const bool profiling_;
   const bool synchronous_;
-  bool active_;
+  Atomic32 active_;
   PlatformData* data_;  // Platform specific data.
 };
 

tools/profiler/sps/v8-support.h

@@ -51,6 +51,15 @@
 #warning Please add support for your architecture in chromium_types.h
 #endif
 
+typedef int32_t Atomic32;
+
+#if defined(V8_HOST_ARCH_X64) || defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_ARM)
+inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
+  *ptr = value;
+}
+#endif
+
+
 const int kMaxInt = 0x7FFFFFFF;
 const int kMinInt = -kMaxInt - 1;