Send SIGPROF signals on the profiler event processor thread

src/platform-linux.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 1109 matching lines @@
 #elif V8_HOST_ARCH_MIPS
   sample->pc = reinterpret_cast<Address>(mcontext.pc);
   sample->sp = reinterpret_cast<Address>(mcontext.gregs[29]);
   sample->fp = reinterpret_cast<Address>(mcontext.gregs[30]);
 #endif  // V8_HOST_ARCH_*
   sampler->SampleStack(sample);
   sampler->Tick(sample);
 }
 
 
-class Sampler::PlatformData : public Malloced {
+class CpuProfilerSignalHandler {
  public:
-  PlatformData() : vm_tid_(GetThreadID()) {}
-
-  int vm_tid() const { return vm_tid_; }
-
- private:
-  const int vm_tid_;
-};
-
-
-class SignalSender : public Thread {
- public:
-  static const int kSignalSenderStackSize = 64 * KB;
-
-  explicit SignalSender(int interval)
-      : Thread(Thread::Options("SignalSender", kSignalSenderStackSize)),
-        vm_tgid_(getpid()),
-        interval_(interval) {}
-
   static void SetUp() { if (!mutex_) mutex_ = OS::CreateMutex(); }
   static void TearDown() { delete mutex_; }
 
+  static bool RegisterProfilingSampler() {
+    ScopedLock lock(mutex_);
+    if (!profiling_samplers_count_) InstallSignalHandler();
+    ++profiling_samplers_count_;
+    return signal_handler_installed_;
+  }
+
+  static void UnregisterProfilingSampler() {
+    ScopedLock lock(mutex_);
+    ASSERT(profiling_samplers_count_ > 0);
+    if (!profiling_samplers_count_) return;
+    if (profiling_samplers_count_ == 1) RestoreSignalHandler();
+    --profiling_samplers_count_;
+  }
+
+ private:
   static void InstallSignalHandler() {
     struct sigaction sa;
     sa.sa_sigaction = ProfilerSignalHandler;
     sigemptyset(&sa.sa_mask);
     sa.sa_flags = SA_RESTART | SA_SIGINFO;
     signal_handler_installed_ =
         (sigaction(SIGPROF, &sa, &old_signal_handler_) == 0);
   }
 
   static void RestoreSignalHandler() {
     if (signal_handler_installed_) {
       sigaction(SIGPROF, &old_signal_handler_, 0);
       signal_handler_installed_ = false;
     }
   }
 
+  // Protects the process wide state below.
+  static Mutex* mutex_;
+  static int profiling_samplers_count_;
+  static bool signal_handler_installed_;
+  static struct sigaction old_signal_handler_;
+};
+
+
+Mutex* CpuProfilerSignalHandler::mutex_ = NULL;
+int CpuProfilerSignalHandler::profiling_samplers_count_ = 0;
+bool CpuProfilerSignalHandler::signal_handler_installed_ = false;
+struct sigaction CpuProfilerSignalHandler::old_signal_handler_;
+
+
+class Sampler::PlatformData : public Malloced {
+ public:
+  PlatformData()
+      : vm_tgid_(getpid()),
+        vm_tid_(GetThreadID()),
+        signal_handler_installed_(false) {}
+
+  void set_signal_handler_installed(bool value) {
+    signal_handler_installed_ = value;
+  }
+
+  void SendProfilingSignal() {
+    if (!signal_handler_installed_) return;
+    // Glibc doesn't provide a wrapper for tgkill(2).
+#if defined(ANDROID)
+    syscall(__NR_tgkill, vm_tgid_, vm_tid_, SIGPROF);
+#else
+    int result = syscall(SYS_tgkill, vm_tgid_, vm_tid_, SIGPROF);
+    USE(result);
+    ASSERT(result == 0);
+#endif
+  }
+
+ private:
+  const int vm_tgid_;
+  const int vm_tid_;
+  bool signal_handler_installed_;
+};
+
+
+class SignalSender : public Thread {
+ public:
+  static const int kSignalSenderStackSize = 64 * KB;
+
+  explicit SignalSender(int interval)
+      : Thread(Thread::Options("SignalSender", kSignalSenderStackSize)),
+        interval_(interval) {}
+
+  static void SetUp() { if (!mutex_) mutex_ = OS::CreateMutex(); }
+  static void TearDown() { delete mutex_; }
+
   static void AddActiveSampler(Sampler* sampler) {
     ScopedLock lock(mutex_);
     SamplerRegistry::AddActiveSampler(sampler);
     if (instance_ == NULL) {
       // Start a thread that will send SIGPROF signal to VM threads,
       // when CPU profiling will be enabled.
       instance_ = new SignalSender(sampler->interval());
       instance_->Start();
     } else {
       ASSERT(instance_->interval_ == sampler->interval());
     }
   }
 
   static void RemoveActiveSampler(Sampler* sampler) {
     ScopedLock lock(mutex_);
     SamplerRegistry::RemoveActiveSampler(sampler);
     if (SamplerRegistry::GetState() == SamplerRegistry::HAS_NO_SAMPLERS) {
       RuntimeProfiler::StopRuntimeProfilerThreadBeforeShutdown(instance_);
       delete instance_;
       instance_ = NULL;
-      RestoreSignalHandler();
     }
   }
 
   // Implement Thread::Run().
   virtual void Run() {
     SamplerRegistry::State state;
     while ((state = SamplerRegistry::GetState()) !=
            SamplerRegistry::HAS_NO_SAMPLERS) {
       // When CPU profiling is enabled both JavaScript and C++ code is
       // profiled. We must not suspend.
       if (state == SamplerRegistry::HAS_CPU_PROFILING_SAMPLERS) {
-        if (!signal_handler_installed_) InstallSignalHandler();
         SamplerRegistry::IterateActiveSamplers(&DoCpuProfile, this);
       } else {
-        if (signal_handler_installed_) RestoreSignalHandler();
         if (RuntimeProfiler::WaitForSomeIsolateToEnterJS()) continue;
       }
       Sleep();  // TODO(svenpanne) Figure out if OS:Sleep(interval_) is enough.
     }
   }
 
   static void DoCpuProfile(Sampler* sampler, void* raw_sender) {
     if (!sampler->IsProfiling()) return;
-    SignalSender* sender = reinterpret_cast<SignalSender*>(raw_sender);
-    sender->SendProfilingSignal(sampler->platform_data()->vm_tid());
-  }
-
-  void SendProfilingSignal(int tid) {
-    if (!signal_handler_installed_) return;
-    // Glibc doesn't provide a wrapper for tgkill(2).
-#if defined(ANDROID)
-    syscall(__NR_tgkill, vm_tgid_, tid, SIGPROF);
-#else
-    int result = syscall(SYS_tgkill, vm_tgid_, tid, SIGPROF);
-    USE(result);
-    ASSERT(result == 0);
-#endif
+    sampler->DoSample();
   }
 
   void Sleep() {
     // Convert ms to us and subtract 100 us to compensate delays
     // occuring during signal delivery.
     useconds_t interval = interval_ * 1000 - 100;
 #if defined(ANDROID)
     usleep(interval);
 #else
     int result = usleep(interval);
 #ifdef DEBUG
     if (result != 0 && errno != EINTR) {
       fprintf(stderr,
               "SignalSender usleep error; interval = %u, errno = %d\n",
               interval,
               errno);
       ASSERT(result == 0 || errno == EINTR);
     }
 #endif  // DEBUG
     USE(result);
 #endif  // ANDROID
   }
 
-  const int vm_tgid_;
   const int interval_;
 
   // Protects the process wide state below.
   static Mutex* mutex_;
   static SignalSender* instance_;
-  static bool signal_handler_installed_;
   static struct sigaction old_signal_handler_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SignalSender);
 };
 
 
 Mutex* SignalSender::mutex_ = NULL;
 SignalSender* SignalSender::instance_ = NULL;
 struct sigaction SignalSender::old_signal_handler_;
-bool SignalSender::signal_handler_installed_ = false;
 
 
 void OS::SetUp() {
   // Seed the random number generator. We preserve microsecond resolution.
   uint64_t seed = Ticks() ^ (getpid() << 16);
   srandom(static_cast<unsigned int>(seed));
   limit_mutex = CreateMutex();
 
 #ifdef __arm__
   // When running on ARM hardware check that the EABI used by V8 and
   // by the C code is the same.
   bool hard_float = OS::ArmUsingHardFloat();
   if (hard_float) {
 #if !USE_EABI_HARDFLOAT
     PrintF("ERROR: Binary compiled with -mfloat-abi=hard but without "
            "-DUSE_EABI_HARDFLOAT\n");
     exit(1);
 #endif
   } else {
 #if USE_EABI_HARDFLOAT
     PrintF("ERROR: Binary not compiled with -mfloat-abi=hard but with "
            "-DUSE_EABI_HARDFLOAT\n");
     exit(1);
 #endif
   }
 #endif
   SignalSender::SetUp();
+  CpuProfilerSignalHandler::SetUp();
 }
 
 
 void OS::TearDown() {
+  CpuProfilerSignalHandler::TearDown();
   SignalSender::TearDown();
   delete limit_mutex;
 }
 
 
 Sampler::Sampler(Isolate* isolate, int interval)
     : isolate_(isolate),
       interval_(interval),
       profiling_(false),
+      has_processing_thread_(false),
       active_(false),
       samples_taken_(0) {
   data_ = new PlatformData;
 }
 
 
 Sampler::~Sampler() {
   ASSERT(!IsActive());
   delete data_;
 }
 
 
 void Sampler::Start() {
   ASSERT(!IsActive());
   SetActive(true);
   SignalSender::AddActiveSampler(this);
 }
 
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 
+bool Sampler::CanSampleOnProfilerEventsProcessorThread() {
+  return true;
+}
+
+
+void Sampler::DoSample() {
+  platform_data()->SendProfilingSignal();
+}
+
+
+void Sampler::StartProfiling() {
+  platform_data()->set_signal_handler_installed(
+      CpuProfilerSignalHandler::RegisterProfilingSampler());
+}
+
+
+void Sampler::StopProfiling() {
+  CpuProfilerSignalHandler::UnregisterProfilingSampler();
+  platform_data()->set_signal_handler_installed(false);
+}
+
+
 } }  // namespace v8::internal