Initial GetSample implementation.

src/sampler.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_SAMPLER_H_
 #define V8_SAMPLER_H_
 
+#include "include/v8.h"
+
 #include "src/base/atomicops.h"
 #include "src/frames.h"
 #include "src/globals.h"
 
 namespace v8 {
 namespace internal {
 
 class Isolate;
 
+class ScopedSemaphore {

[alph, 2014/09/09 13:54:37]

Move it into the cc file?

+ public:
+  explicit ScopedSemaphore(base::Semaphore* sem) { semaphore_ = sem; }
+  ~ScopedSemaphore() { semaphore_->Signal(); }
+
+ private:
+  base::Semaphore* semaphore_;

[yurys, 2014/09/09 14:35:20]

semaphore.h would be a more appropriate place for this.

[gholap, 2014/09/17 02:35:06]

Yes agreed. Another alternative could be, as alph suggested, to move it to the
cc file. I'm more inclined toward moving it to .cc file because this doesn't
look like a terribly useful thing to make it general. But yes, I might be
completely wrong about that, I would love your input on this.

+};
+
+
 // ----------------------------------------------------------------------------
 // Sampler
 //
 // A sampler periodically samples the state of the VM and optionally
 // (if used for profiling) the program counter and stack pointer for
 // the thread that created it.
 
 struct RegisterState {
   RegisterState() : pc(NULL), sp(NULL), fp(NULL) {}
   Address pc;      // Instruction pointer.
   Address sp;      // Stack pointer.
   Address fp;      // Frame pointer.
 };
 
 // TickSample captures the information collected for each sample.
 struct TickSample {
   TickSample()
       : state(OTHER),
         pc(NULL),
         external_callback(NULL),
-        frames_count(0),
         has_external_callback(false),
         top_frame_type(StackFrame::NONE) {}
   void Init(Isolate* isolate, const RegisterState& state);
-  StateTag state;  // The state of the VM.
-  Address pc;      // Instruction pointer.
+  enum { kMaxFramesCount = 255u };
+
+  void* stack[kMaxFramesCount];  // Call stack.
+  size_t frames_count;           // Number of captured frames.
+  StateTag state;                // The state of the VM.
+  Address pc;                    // Instruction pointer.
   union {
     Address tos;   // Top stack value (*sp).
     Address external_callback;
   };
-  static const unsigned kMaxFramesCountLog2 = 8;
-  static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
-  Address stack[kMaxFramesCount];  // Call stack.
   base::TimeTicks timestamp;
-  unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
   bool has_external_callback : 1;
   StackFrame::Type top_frame_type : 4;
 };
 
 class Sampler {
  public:
   // Initializes the Sampler support. Called once at VM startup.
   static void SetUp();
   static void TearDown();
 
@@ skipping 16 matching lines @@
     return base::NoBarrier_Load(&profiling_) > 0 &&
         !base::NoBarrier_Load(&has_processing_thread_);
   }
   void IncreaseProfilingDepth();
   void DecreaseProfilingDepth();
 
   // Whether the sampler is running (that is, consumes resources).
   bool IsActive() const { return base::NoBarrier_Load(&active_); }
 
   void DoSample();
+  void GetSample(v8::Sample* sample);
   // If true next sample must be initiated on the profiler event processor
   // thread right after latest sample is processed.
   void SetHasProcessingThread(bool value) {
     base::NoBarrier_Store(&has_processing_thread_, value);
   }
 
   // Used in tests to make sure that stack sampling is performed.
   unsigned js_and_external_sample_count() const {
     return js_and_external_sample_count_;
   }
@@ skipping 15 matching lines @@
 
   Isolate* isolate_;
   const int interval_;
   base::Atomic32 profiling_;
   base::Atomic32 has_processing_thread_;
   base::Atomic32 active_;
   PlatformData* data_;  // Platform specific data.
   bool is_counting_samples_;
   // Counts stack samples taken in JS VM state.
   unsigned js_and_external_sample_count_;
+  void GetSampleHelper(TickSample* sample, bool called_from_get_sample);
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SAMPLER_H_