Make Profiler::tail_ atomic

src/log.cc

 // Copyright 2011 the V8 project 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 "src/log.h"
 
 #include <cstdarg>
 #include <sstream>
 
 #include "src/v8.h"
@@ skipping 589 matching lines @@
  public:
   explicit Profiler(Isolate* isolate);
   void Engage();
   void Disengage();
 
   // Inserts collected profiling data into buffer.
   void Insert(TickSample* sample) {
     if (paused_)
       return;
 
-    if (Succ(head_) == tail_) {
+    if (Succ(head_) == static_cast<int>(base::NoBarrier_Load(&tail_))) {
       overflow_ = true;
     } else {
       buffer_[head_] = *sample;
       head_ = Succ(head_);
       buffer_semaphore_.Signal();  // Tell we have an element.
     }
   }
 
   virtual void Run();
 
   // Pause and Resume TickSample data collection.
   void pause() { paused_ = true; }
   void resume() { paused_ = false; }
 
  private:
   // Waits for a signal and removes profiling data.
   bool Remove(TickSample* sample) {
     buffer_semaphore_.Wait();  // Wait for an element.
-    *sample = buffer_[tail_];
+    *sample = buffer_[base::NoBarrier_Load(&tail_)];
     bool result = overflow_;
-    tail_ = Succ(tail_);
+    base::NoBarrier_Store(&tail_, static_cast<base::Atomic32>(
+                                      Succ(base::NoBarrier_Load(&tail_))));
     overflow_ = false;
     return result;
   }
 
   // Returns the next index in the cyclic buffer.
   int Succ(int index) { return (index + 1) % kBufferSize; }
 
   Isolate* isolate_;
   // Cyclic buffer for communicating profiling samples
   // between the signal handler and the worker thread.
   static const int kBufferSize = 128;
   TickSample buffer_[kBufferSize];  // Buffer storage.
   int head_;  // Index to the buffer head.
-  int tail_;  // Index to the buffer tail.
+  base::Atomic32 tail_;             // Index to the buffer tail.
   bool overflow_;  // Tell whether a buffer overflow has occurred.
   // Sempahore used for buffer synchronization.
   base::Semaphore buffer_semaphore_;
 
   // Tells whether profiler is engaged, that is, processing thread is stated.
   bool engaged_;
 
   // Tells whether worker thread should continue running.
   bool running_;
 
@@ skipping 36 matching lines @@
 };
 
 
 //
 // Profiler implementation.
 //
 Profiler::Profiler(Isolate* isolate)
     : base::Thread(Options("v8:Profiler")),
       isolate_(isolate),
       head_(0),
-      tail_(0),
       overflow_(false),
       buffer_semaphore_(0),
       engaged_(false),
       running_(false),
-      paused_(false) {}
+      paused_(false) {
+  base::NoBarrier_Store(&tail_, 0);
+}
 
 
 void Profiler::Engage() {
   if (engaged_) return;
   engaged_ = true;
 
   std::vector<base::OS::SharedLibraryAddress> addresses =
       base::OS::GetSharedLibraryAddresses();
   for (size_t i = 0; i < addresses.size(); ++i) {
     LOG(isolate_, SharedLibraryEvent(
@@ skipping 1218 matching lines @@
   if (jit_logger_) {
     removeCodeEventListener(jit_logger_);
     delete jit_logger_;
     jit_logger_ = NULL;
   }
 
   return log_->Close();
 }
 
 } }  // namespace v8::internal