1 files changed, 80 insertions, 37 deletions

diff --git a/deps/v8/src/libsampler/sampler.h b/deps/v8/src/libsampler/sampler.h
index 6ce6798a44..8e39a95f58 100644
--- a/deps/v8/src/libsampler/sampler.h
+++ b/deps/v8/src/libsampler/sampler.h
@@ -5,11 +5,17 @@
 #ifndef V8_LIBSAMPLER_SAMPLER_H_
 #define V8_LIBSAMPLER_SAMPLER_H_
 
-#include "include/v8.h"
+#include <atomic>
+#include <unordered_map>
 
-#include "src/base/atomicops.h"
+#include "include/v8.h"
+#include "src/base/lazy-instance.h"
 #include "src/base/macros.h"
 
+#if V8_OS_POSIX && !V8_OS_CYGWIN && !V8_OS_FUCHSIA
+#define USE_SIGNALS
+#endif
+
 namespace v8 {
 namespace sampler {
 
@@ -25,10 +31,6 @@ class Sampler {
   static const int kMaxFramesCountLog2 = 8;
   static const unsigned kMaxFramesCount = (1u << kMaxFramesCountLog2) - 1;
 
-  // Initializes the Sampler support. Called once at VM startup.
-  static void SetUp();
-  static void TearDown();
-
   // Initialize sampler.
   explicit Sampler(Isolate* isolate);
   virtual ~Sampler();
@@ -44,28 +46,11 @@ class Sampler {
   void Start();
   void Stop();
 
-  // Whether the sampling thread should use this Sampler for CPU profiling?
-  bool IsProfiling() const {
-    return base::Relaxed_Load(&profiling_) > 0 &&
-           !base::Relaxed_Load(&has_processing_thread_);
-  }
-  void IncreaseProfilingDepth();
-  void DecreaseProfilingDepth();
-
-  // Whether the sampler is running (that is, consumes resources).
-  bool IsActive() const { return base::Relaxed_Load(&active_) != 0; }
-
-  // CpuProfiler collects samples by calling DoSample directly
-  // without calling Start. To keep it working, we register the sampler
-  // with the CpuProfiler.
-  bool IsRegistered() const { return base::Relaxed_Load(&registered_) != 0; }
+  // Whether the sampler is running (start has been called).
+  bool IsActive() const { return active_.load(std::memory_order_relaxed); }
 
   void DoSample();
 
-  void SetHasProcessingThread(bool value) {
-    base::Relaxed_Store(&has_processing_thread_, value);
-  }
-
   // Used in tests to make sure that stack sampling is performed.
   unsigned js_sample_count() const { return js_sample_count_; }
   unsigned external_sample_count() const { return external_sample_count_; }
@@ -76,27 +61,85 @@ class Sampler {
   }
 
   class PlatformData;
-  PlatformData* platform_data() const { return data_; }
+  PlatformData* platform_data() const { return data_.get(); }
 
  protected:
   // Counts stack samples taken in various VM states.
-  bool is_counting_samples_;
-  unsigned js_sample_count_;
-  unsigned external_sample_count_;
+  bool is_counting_samples_ = 0;
+  unsigned js_sample_count_ = 0;
+  unsigned external_sample_count_ = 0;
 
- private:
-  void SetActive(bool value) { base::Relaxed_Store(&active_, value); }
-  void SetRegistered(bool value) { base::Relaxed_Store(&registered_, value); }
+  void SetActive(bool value) {
+    active_.store(value, std::memory_order_relaxed);
+  }
 
   Isolate* isolate_;
-  base::Atomic32 profiling_;
-  base::Atomic32 has_processing_thread_;
-  base::Atomic32 active_;
-  base::Atomic32 registered_;
-  PlatformData* data_;  // Platform specific data.
+  std::atomic_bool active_{false};
+  std::unique_ptr<PlatformData> data_;  // Platform specific data.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
+#ifdef USE_SIGNALS
+
+typedef std::atomic_bool AtomicMutex;
+
+// A helper that uses an std::atomic_bool to create a lock that is obtained on
+// construction and released on destruction.
+class AtomicGuard {
+ public:
+  // Attempt to obtain the lock represented by |atomic|. |is_blocking|
+  // determines whether we will block to obtain the lock, or only make one
+  // attempt to gain the lock and then stop. If we fail to gain the lock,
+  // is_success will be false.
+  explicit AtomicGuard(AtomicMutex* atomic, bool is_blocking = true);
+
+  // Releases the lock represented by atomic, if it is held by this guard.
+  ~AtomicGuard();
+
+  // Whether the lock was successfully obtained in the constructor. This will
+  // always be true if is_blocking was true.
+  bool is_success() const;
+
+ private:
+  AtomicMutex* const atomic_;
+  bool is_success_;
+};
+
+// SamplerManager keeps a list of Samplers per thread, and allows the caller to
+// take a sample for every Sampler on the current thread.
+class SamplerManager {
+ public:
+  typedef std::vector<Sampler*> SamplerList;
+
+  // Add |sampler| to the map if it is not already present.
+  void AddSampler(Sampler* sampler);
+
+  // If |sampler| exists in the map, remove it and delete the SamplerList if
+  // |sampler| was the last sampler in the list.
+  void RemoveSampler(Sampler* sampler);
+
+  // Take a sample for every sampler on the current thread. This function can
+  // return without taking samples if AddSampler or RemoveSampler are being
+  // concurrently called on any thread.
+  void DoSample(const v8::RegisterState& state);
+
+  // Get the lazily instantiated, global SamplerManager instance.
+  static SamplerManager* instance();
+
+ private:
+  SamplerManager() = default;
+  // Must be a friend so that it can access the private constructor for the
+  // global lazy instance.
+  friend class base::LeakyObject<SamplerManager>;
+
+  std::unordered_map<pthread_t, SamplerList> sampler_map_;
+  AtomicMutex samplers_access_counter_{false};
+
+  DISALLOW_COPY_AND_ASSIGN(SamplerManager);
+};
+
+#endif  // USE_SIGNALS
+
 }  // namespace sampler
 }  // namespace v8