GpuScheduler no longer spins when it is waiting on a latch.

BUG=79632
TEST=run trace in about:gpu; observe the number of times the GPU process sequentially calls WaitLatch; verify it is not spinning.

Review URL: http://codereview.chromium.org/6874029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@82033 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 36 insertions, 7 deletions

diff --git a/gpu/command_buffer/common/constants.h b/gpu/command_buffer/common/constants.h
index bebc046..6ef22aa 100644
--- a/gpu/command_buffer/common/constants.h
+++ b/gpu/command_buffer/common/constants.h
@@ -23,9 +23,9 @@ namespace error {
     kLostContext,
     kGenericError,
 
-    // This is not an error. It is returned by commands that want to
-    // be called again until they return a different error. For
-    // example: WaitLatch.
+    // This is not an error. It is returned by WaitLatch when it is blocked.
+    // When blocked, the context will not reschedule itself until another
+    // context executes a SetLatch command.
     kWaiting,
 
     // This is not an error. It is returned by commands to mark a position
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 2c0de18..9e14183 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -686,6 +686,7 @@ class GLES2DecoderImpl : public base::SupportsWeakPtr<GLES2DecoderImpl>,
 
   virtual void SetResizeCallback(Callback1<gfx::Size>::Type* callback);
   virtual void SetSwapBuffersCallback(Callback0::Type* callback);
+  virtual void SetLatchCallback(const base::Callback<void(bool)>& callback);;
   virtual bool GetServiceTextureId(uint32 client_texture_id,
                                    uint32* service_texture_id);
 
@@ -1447,6 +1448,7 @@ class GLES2DecoderImpl : public base::SupportsWeakPtr<GLES2DecoderImpl>,
 
   scoped_ptr<Callback1<gfx::Size>::Type> resize_callback_;
   scoped_ptr<Callback0::Type> swap_buffers_callback_;
+  base::Callback<void(bool)> latch_callback_;
 
   // The format of the back buffer_
   GLenum back_buffer_color_format_;
@@ -2458,6 +2460,11 @@ void GLES2DecoderImpl::SetSwapBuffersCallback(Callback0::Type* callback) {
   swap_buffers_callback_.reset(callback);
 }
 
+void GLES2DecoderImpl::SetLatchCallback(
+    const base::Callback<void(bool)>& callback) {
+  latch_callback_ = callback;
+}
+
 bool GLES2DecoderImpl::GetServiceTextureId(uint32 client_texture_id,
                                            uint32* service_texture_id) {
   TextureManager::TextureInfo* texture =
@@ -6398,7 +6405,9 @@ error::Error GLES2DecoderImpl::HandleSetLatchCHROMIUM(
   if (!latch) {
     return error::kOutOfBounds;
   }
-  *latch = 1;
+  base::subtle::NoBarrier_Store(latch, 1);
+  if (!latch_callback_.is_null())
+    latch_callback_.Run(true);
   return error::kNoError;
 }
 
@@ -6419,7 +6428,13 @@ error::Error GLES2DecoderImpl::HandleWaitLatchCHROMIUM(
 
   base::subtle::Atomic32 old =
       base::subtle::NoBarrier_CompareAndSwap(latch, 1, 0);
-  return (old == 0) ? error::kWaiting : error::kNoError;
+  if (old == 0) {
+    if (!latch_callback_.is_null())
+      latch_callback_.Run(false);
+    return error::kWaiting;
+  } else {
+    return error::kNoError;
+  }
 }
 
 error::Error GLES2DecoderImpl::HandleCommandBufferEnableCHROMIUM(
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.h b/gpu/command_buffer/service/gles2_cmd_decoder.h
index 1646c90..cb28d21 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.h
@@ -103,6 +103,11 @@ class GLES2Decoder : public CommonDecoder {
   // Sets a callback which is called when a SwapBuffers command is processed.
   virtual void SetSwapBuffersCallback(Callback0::Type* callback) = 0;
 
+  // Sets a callback which is called after a Set/WaitLatch command is processed.
+  // The bool parameter will be true for SetLatch, and false for a WaitLatch
+  // that is blocked. An unblocked WaitLatch will not trigger a callback.
+  virtual void SetLatchCallback(const base::Callback<void(bool)>& callback) = 0;
+
   // Get the service texture ID corresponding to a client texture ID.
   // If no such record is found then return false.
   virtual bool GetServiceTextureId(uint32 client_texture_id,
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_mock.h b/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
index 37a7e72..3ab6f06 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
@@ -43,6 +43,7 @@ class MockGLES2Decoder : public GLES2Decoder {
   MOCK_METHOD0(GetContextGroup, ContextGroup*());
   MOCK_METHOD1(SetResizeCallback, void(Callback1<gfx::Size>::Type*));
   MOCK_METHOD1(SetSwapBuffersCallback, void(Callback0::Type*));
+  MOCK_METHOD1(SetLatchCallback, void(const base::Callback<void(bool)>&));
   MOCK_METHOD3(DoCommand, error::Error(unsigned int command,
                                        unsigned int arg_count,
                                        const void* cmd_data));
diff --git a/gpu/command_buffer/service/gpu_scheduler.cc b/gpu/command_buffer/service/gpu_scheduler.cc
index 933b468..1ae36c4 100644
--- a/gpu/command_buffer/service/gpu_scheduler.cc
+++ b/gpu/command_buffer/service/gpu_scheduler.cc
@@ -166,9 +166,10 @@ void GpuScheduler::ProcessCommands() {
     throttle_fences_.pop();
   }
 
+  error::Error error = error::kNoError;
   int commands_processed = 0;
   while (commands_processed < commands_per_update_ && !parser_->IsEmpty()) {
-    error::Error error = parser_->ProcessCommand();
+    error = parser_->ProcessCommand();
     if (error == error::kWaiting) {
       break;
     }
@@ -201,7 +202,7 @@ void GpuScheduler::ProcessCommands() {
 
   command_buffer_->SetGetOffset(static_cast<int32>(parser_->get()));
 
-  if (!parser_->IsEmpty()) {
+  if (error != error::kWaiting && !parser_->IsEmpty()) {
     ScheduleProcessCommands();
   }
 }
diff --git a/gpu/command_buffer/service/gpu_scheduler.h b/gpu/command_buffer/service/gpu_scheduler.h
index 5ed808c..36cc009 100644
--- a/gpu/command_buffer/service/gpu_scheduler.h
+++ b/gpu/command_buffer/service/gpu_scheduler.h
@@ -114,6 +114,13 @@ class GpuScheduler : public CommandBufferEngine {
 
   virtual void SetCommandProcessedCallback(Callback0::Type* callback);
 
+  // Sets a callback which is called after a Set/WaitLatch command is processed.
+  // The bool parameter will be true for SetLatch, and false for a WaitLatch
+  // that is blocked. An unblocked WaitLatch will not trigger a callback.
+  void SetLatchCallback(const base::Callback<void(bool)>& callback) {
+    decoder_->SetLatchCallback(callback);
+  }
+
   // Get the GLES2Decoder associated with this scheduler.
   gles2::GLES2Decoder* decoder() const { return decoder_.get(); }