Use signals for cpu profiling on Mac OS X

src/cpu-profiler.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 418 matching lines @@
   if (processor_ == NULL) {
     Logger* logger = isolate_->logger();
     // Disable logging when using the new implementation.
     saved_logging_nesting_ = logger->logging_nesting_;
     logger->logging_nesting_ = 0;
     generator_ = new ProfileGenerator(profiles_);
     Sampler* sampler = logger->sampler();
     processor_ = new ProfilerEventsProcessor(
         generator_, sampler, FLAG_cpu_profiler_sampling_interval);
     is_profiling_ = true;
-    processor_->StartSynchronously();
     // Enumerate stuff we already have in the heap.
     ASSERT(isolate_->heap()->HasBeenSetUp());
     if (!FLAG_prof_browser_mode) {
       logger->LogCodeObjects();
     }
     logger->LogCompiledFunctions();
     logger->LogAccessorCallbacks();
     LogBuiltins();
     // Enable stack sampling.
     if (Sampler::CanSampleOnProfilerEventsProcessorThread()) {
       sampler->SetHasProcessingThread(true);
     }
     sampler->IncreaseProfilingDepth();
     if (!sampler->IsActive()) {
       sampler->Start();
       need_to_stop_sampler_ = true;
     }
+    processor_->StartSynchronously();
   }
 }
 
 
 CpuProfile* CpuProfiler::StopProfiling(const char* title) {
   if (!is_profiling_) return NULL;
   StopProcessorIfLastProfile(title);
   CpuProfile* result = profiles_->StopProfiling(title);
   if (result != NULL) {
     result->Print();
@@ skipping 44 matching lines @@
     ReportBuiltinEventRecord* rec = &evt_rec.ReportBuiltinEventRecord_;
     Builtins::Name id = static_cast<Builtins::Name>(i);
     rec->start = builtins->builtin(id)->address();
     rec->builtin_id = id;
     processor_->Enqueue(evt_rec);
   }
 }
 
 
 } }  // namespace v8::internal