Replacing circular queue by single buffer in CPU Profiler.

src/platform-macos.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 791 matching lines @@
     sampler_thread->SampleContext(sampler);
   }
 
   static void DoRuntimeProfile(Sampler* sampler, void* ignored) {
     if (!sampler->isolate()->IsInitialized()) return;
     sampler->isolate()->runtime_profiler()->NotifyTick();
   }
 
   void SampleContext(Sampler* sampler) {
     thread_act_t profiled_thread = sampler->platform_data()->profiled_thread();
-    TickSample sample_obj;
-    TickSample* sample = CpuProfiler::TickSampleEvent(sampler->isolate());
-    if (sample == NULL) sample = &sample_obj;
+    TickSample* sample = CpuProfiler::StartTickSampleEvent(sampler->isolate());
+    if (sample == NULL) return;
 
     if (KERN_SUCCESS != thread_suspend(profiled_thread)) return;
 
 #if V8_HOST_ARCH_X64
     thread_state_flavor_t flavor = x86_THREAD_STATE64;
     x86_thread_state64_t state;
     mach_msg_type_number_t count = x86_THREAD_STATE64_COUNT;
 #if __DARWIN_UNIX03
 #define REGISTER_FIELD(name) __r ## name
 #else
@@ skipping 16 matching lines @@
                          flavor,
                          reinterpret_cast<natural_t*>(&state),
                          &count) == KERN_SUCCESS) {
       sample->state = sampler->isolate()->current_vm_state();
       sample->pc = reinterpret_cast<Address>(state.REGISTER_FIELD(ip));
       sample->sp = reinterpret_cast<Address>(state.REGISTER_FIELD(sp));
       sample->fp = reinterpret_cast<Address>(state.REGISTER_FIELD(bp));
       sampler->SampleStack(sample);
       sampler->Tick(sample);
     }
+    CpuProfiler::FinishTickSampleEvent(sampler->isolate());
     thread_resume(profiled_thread);
   }
 
   const int interval_;
   RuntimeProfilerRateLimiter rate_limiter_;
 
   // Protects the process wide state below.
   static Mutex* mutex_;
   static SamplerThread* instance_;
 
@@ skipping 52 matching lines @@
 
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SamplerThread::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 
 } }  // namespace v8::internal