Rework FlushSync to return early if commands have been processed since the last update

gpu/command_buffer/service/command_buffer_service.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/command_buffer_service.h"
 
 #include <limits>
 
 #include "base/callback.h"
 #include "base/process_util.h"
 #include "gpu/command_buffer/common/cmd_buffer_common.h"
 
 using ::base::SharedMemory;
 
 namespace gpu {
 
 CommandBufferService::CommandBufferService()
     : num_entries_(0),
       get_offset_(0),
       put_offset_(0),
       token_(0),
+      generation_(0),
       error_(error::kNoError) {
   // Element zero is always NULL.
   registered_objects_.push_back(Buffer());
 }
 
 CommandBufferService::~CommandBufferService() {
   delete ring_buffer_.shared_memory;
 
   for (size_t i = 0; i < registered_objects_.size(); ++i) {
     if (registered_objects_[i].shared_memory)
@@ skipping 58 matching lines @@
   return ring_buffer_;
 }
 
 CommandBufferService::State CommandBufferService::GetState() {
   State state;
   state.num_entries = num_entries_;
   state.get_offset = get_offset_;
   state.put_offset = put_offset_;
   state.token = token_;
   state.error = error_;
+  state.generation = ++generation_;
 
   return state;
 }
 
-CommandBufferService::State CommandBufferService::FlushSync(int32 put_offset) {
+CommandBufferService::State CommandBufferService::FlushSync(
+    int32 put_offset, int32 last_known_get) {
   if (put_offset < 0 || put_offset > num_entries_) {
     error_ = gpu::error::kOutOfBounds;
     return GetState();
   }
 
   put_offset_ = put_offset;
 
   if (put_offset_change_callback_.get()) {
-    put_offset_change_callback_->Run();
+    put_offset_change_callback_->Run(last_known_get == get_offset_);
   }
 
   return GetState();
 }
 
 void CommandBufferService::Flush(int32 put_offset) {
-  FlushSync(put_offset);
+  if (put_offset < 0 || put_offset > num_entries_) {
+    error_ = gpu::error::kOutOfBounds;
+    return;
+  }
+
+  put_offset_ = put_offset;
+
+  if (put_offset_change_callback_.get()) {
+    put_offset_change_callback_->Run(false);
+  }
 }
 
 void CommandBufferService::SetGetOffset(int32 get_offset) {
   DCHECK(get_offset >= 0 && get_offset < num_entries_);
   get_offset_ = get_offset;
 }
 
 int32 CommandBufferService::CreateTransferBuffer(size_t size,
                                                  int32 id_request) {
   SharedMemory buffer;
@@ skipping 103 matching lines @@
   token_ = token;
 }
 
 void CommandBufferService::SetParseError(error::Error error) {
   if (error_ == error::kNoError) {
     error_ = error;
   }
 }
 
 void CommandBufferService::SetPutOffsetChangeCallback(
-    Callback0::Type* callback) {
+    Callback1<bool>::Type* callback) {
   put_offset_change_callback_.reset(callback);
 }
 
 }  // namespace gpu