Perform CPU sampling by CPU sampling thread only iff processing thread is not running.

src/platform-linux.cc

Index: src/platform-linux.cc
diff --git a/src/platform-linux.cc b/src/platform-linux.cc
index d5ac6fa4642db1333db703f49657ba389885e63e..d200c0c21885301e3ea13d03160518845b0c3a84 100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -1020,6 +1020,7 @@ static int GetThreadID() {
 static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   USE(info);
   if (signal != SIGPROF) return;
+
   Isolate* isolate = Isolate::UncheckedCurrent();
   if (isolate == NULL || !isolate->IsInitialized() || !isolate->IsInUse()) {
     // We require a fully initialized and entered isolate.
@@ -1033,8 +1034,9 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
+  TickSample sample_obj;
   TickSample* sample = CpuProfiler::StartTickSampleEvent(isolate);
-  if (sample == NULL) return;
+  if (sample == NULL) sample = &sample_obj;
 
   // Extracting the sample from the context is extremely machine dependent.
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
@@ -1185,16 +1187,45 @@ class SignalSender : public Thread {
     SamplerRegistry::State state;
     while ((state = SamplerRegistry::GetState()) !=
            SamplerRegistry::HAS_NO_SAMPLERS) {
-      if (rate_limiter_.SuspendIfNecessary()) continue;
-      if (RuntimeProfiler::IsEnabled()) {
+      bool cpu_profiling_enabled =
+          (state == SamplerRegistry::HAS_CPU_PROFILING_SAMPLERS);
+      bool runtime_profiler_enabled = RuntimeProfiler::IsEnabled();
+      // When CPU profiling is enabled both JavaScript and C++ code is
+      // profiled. We must not suspend.
+      if (!cpu_profiling_enabled) {
+        if (rate_limiter_.SuspendIfNecessary()) continue;
+      }
+      if (cpu_profiling_enabled && runtime_profiler_enabled) {
+        if (!SamplerRegistry::IterateActiveSamplers(&DoCpuProfile, NULL)) {
+          return;
+        }
+        Sleep(HALF_INTERVAL);
         if (!SamplerRegistry::IterateActiveSamplers(&DoRuntimeProfile, NULL)) {
           return;
         }
+        Sleep(HALF_INTERVAL);
+      } else {
+        if (cpu_profiling_enabled) {
+          if (!SamplerRegistry::IterateActiveSamplers(&DoCpuProfile, NULL)) {
+            return;
+          }
+        }
+        if (runtime_profiler_enabled) {
+          if (!SamplerRegistry::IterateActiveSamplers(&DoRuntimeProfile,
+                                                      NULL)) {
+            return;
+          }
+        }
+        Sleep(FULL_INTERVAL);
       }
-      Sleep(FULL_INTERVAL);
     }
   }
 
+  static void DoCpuProfile(Sampler* sampler, void*) {
+    if (!sampler->IsProfiling()) return;
+    sampler->platform_data()->SendProfilingSignal();
+  }
+
   static void DoRuntimeProfile(Sampler* sampler, void* ignored) {
     if (!sampler->isolate()->IsInitialized()) return;
     sampler->isolate()->runtime_profiler()->NotifyTick();
@@ -1279,6 +1310,7 @@ Sampler::Sampler(Isolate* isolate, int interval)
       interval_(interval),
       profiling_(false),
       active_(false),
+      has_processing_thread_(false),
       samples_taken_(0) {
   data_ = new PlatformData;
 }
@@ -1297,7 +1329,6 @@ void Sampler::DoSample() {
 
 void Sampler::Start() {
   ASSERT(!IsActive());
-  CpuProfilerSignalHandler::InstallSignalHandler();
   SetActive(true);
   SignalSender::AddActiveSampler(this);
 }
@@ -1305,10 +1336,19 @@ void Sampler::Start() {
 
 void Sampler::Stop() {
   ASSERT(IsActive());
-  CpuProfilerSignalHandler::RestoreSignalHandler();
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 
+void Sampler::StartSampling() {
+  CpuProfilerSignalHandler::InstallSignalHandler();
+}
+
+
+void Sampler::StopSampling() {
+  CpuProfilerSignalHandler::RestoreSignalHandler();
+}
+
+
 } }  // namespace v8::internal