Send SIGPROF signals on the profiler event processor thread

src/cpu-profiler.cc

Index: src/cpu-profiler.cc
diff --git a/src/cpu-profiler.cc b/src/cpu-profiler.cc
index 3cbac77858d5560feb3cab420f08c9e461f2422e..9a7567c5d9034f1aba2f94a9b46bfcf11678b000 100644
--- a/src/cpu-profiler.cc
+++ b/src/cpu-profiler.cc
@@ -45,13 +45,18 @@ static const int kTickSamplesBufferChunksCount = 16;
 static const int kProfilerStackSize = 64 * KB;
 
 
-ProfilerEventsProcessor::ProfilerEventsProcessor(ProfileGenerator* generator)
+ProfilerEventsProcessor::ProfilerEventsProcessor(ProfileGenerator* generator,
+                                                 Sampler* sampler,
+                                                 int period_in_useconds)
     : Thread(Thread::Options("v8:ProfEvntProc", kProfilerStackSize)),
       generator_(generator),
+      sampler_(sampler),
       running_(true),
+      period_in_useconds_(period_in_useconds),
       ticks_buffer_(sizeof(TickSampleEventRecord),
                     kTickSamplesBufferChunkSize,
-                    kTickSamplesBufferChunksCount),
+                    kTickSamplesBufferChunksCount,
+                    !Sampler::CanSampleOnProfilerEventsProcessorThread()),
       enqueue_order_(0) {
 }
 
@@ -239,17 +244,42 @@ bool ProfilerEventsProcessor::ProcessTicks(unsigned dequeue_order) {
 }
 
 
+void ProfilerEventsProcessor::ProcessEventsAndDoSample(
+    unsigned* dequeue_order) {
+  int64_t stop_time = OS::Ticks() + period_in_useconds_;
+  // Keep processing existing events until we need to do next sample.
+  while (OS::Ticks() < stop_time) {
+    if (ProcessTicks(*dequeue_order)) {
+      // All ticks of the current dequeue_order are processed,
+      // proceed to the next code event.
+      ProcessCodeEvent(dequeue_order);
+    }
+  }
+  // Schedule next sample. sampler_ is NULL in tests.
+  if (sampler_)
+    sampler_->DoSample();
+}
+
+
+void ProfilerEventsProcessor::ProcessEventsAndYield(unsigned* dequeue_order) {
+  if (ProcessTicks(*dequeue_order)) {
+    // All ticks of the current dequeue_order are processed,
+    // proceed to the next code event.
+    ProcessCodeEvent(dequeue_order);
+  }
+  YieldCPU();
+}
+
+
 void ProfilerEventsProcessor::Run() {
   unsigned dequeue_order = 0;
 
   while (running_) {
-    // Process ticks until we have any.
-    if (ProcessTicks(dequeue_order)) {
-      // All ticks of the current dequeue_order are processed,
-      // proceed to the next code event.
-      ProcessCodeEvent(&dequeue_order);
+    if (Sampler::CanSampleOnProfilerEventsProcessorThread()) {
+      ProcessEventsAndDoSample(&dequeue_order);
+    } else {
+      ProcessEventsAndYield(&dequeue_order);
     }
-    YieldCPU();
   }
 
   // Process remaining tick events.
@@ -486,13 +516,15 @@ void CpuProfiler::StartProcessorIfNotStarted() {
   if (processor_ == NULL) {
     Isolate* isolate = Isolate::Current();
 
+    Sampler* sampler = reinterpret_cast<Sampler*>(isolate->logger()->ticker_);
     // Disable logging when using the new implementation.
     saved_logging_nesting_ = isolate->logger()->logging_nesting_;
     isolate->logger()->logging_nesting_ = 0;
     generator_ = new ProfileGenerator(profiles_);
-    processor_ = new ProfilerEventsProcessor(generator_);
+    processor_ = new ProfilerEventsProcessor(generator_,
+                                             sampler,
+                                             FLAG_cpu_profiler_sampling_period);
     NoBarrier_Store(&is_profiling_, true);
-    processor_->Start();
     // Enumerate stuff we already have in the heap.
     if (isolate->heap()->HasBeenSetUp()) {
       if (!FLAG_prof_browser_mode) {
@@ -505,12 +537,13 @@ void CpuProfiler::StartProcessorIfNotStarted() {
       isolate->logger()->LogAccessorCallbacks();
     }
     // Enable stack sampling.
-    Sampler* sampler = reinterpret_cast<Sampler*>(isolate->logger()->ticker_);
     if (!sampler->IsActive()) {
       sampler->Start();
       need_to_stop_sampler_ = true;
     }
+    sampler->SetHasProcessingThread(true);
     sampler->IncreaseProfilingDepth();
+    processor_->Start();
   }
 }
 
@@ -548,6 +581,7 @@ void CpuProfiler::StopProcessor() {
   Logger* logger = Isolate::Current()->logger();
   Sampler* sampler = reinterpret_cast<Sampler*>(logger->ticker_);
   sampler->DecreaseProfilingDepth();
+  sampler->SetHasProcessingThread(false);
   if (need_to_stop_sampler_) {
     sampler->Stop();
     need_to_stop_sampler_ = false;