Revert 122034 - Use shared memory to update the renderer's view of the command buffer state.

The renderer can't receive UpdateState messages while it's executing javascript or NaCl, causing it to eventually flushsync once it fills up the command buffer or transfer buffer. To avoid this, share a piece of memory between the renderer and gpu process that the GPU can asynchronously update the state. A 4-slot asynchronous communication mechanism is used so that the renderer always receives a consistent copy of the state that was put in by the GPU process.

BUG=114397
TEST=


Review URL: http://codereview.chromium.org/9380037

TBR=jbauman@chromium.org
Review URL: https://chromiumcodereview.appspot.com/9403022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@122116 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 0 insertions, 185 deletions

diff --git a/gpu/command_buffer/common/command_buffer_shared.h b/gpu/command_buffer/common/command_buffer_shared.h
deleted file mode 100644
index 017a644..0000000
--- a/gpu/command_buffer/common/command_buffer_shared.h
+++ /dev/null
@@ -1,61 +0,0 @@
-// Copyright (c) 2012 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.
-
-#ifndef GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_
-#define GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_
-
-#include "command_buffer.h"
-#include "base/atomicops.h"
-
-namespace gpu {
-
-// This is a standard 4-slot asynchronous communication mechanism, used to
-// ensure that the reader gets a consistent copy of what the writer wrote.
-template<typename T>
-class SharedState {
-  T states_[2][2];
-  base::subtle::Atomic32 reading_;
-  base::subtle::Atomic32 latest_;
-  base::subtle::Atomic32 slots_[2];
-
-public:
-
-  void Initialize() {
-    for (int i = 0; i < 2; ++i) {
-      for (int j = 0; j < 2; ++j) {
-        states_[i][j] = T();
-      }
-    }
-    base::subtle::NoBarrier_Store(&reading_, 0);
-    base::subtle::NoBarrier_Store(&latest_, 0);
-    base::subtle::NoBarrier_Store(&slots_[0], 0);
-    base::subtle::Acquire_Store(&slots_[1], 0);
-  }
-
-  void Write(const T& state) {
-    int towrite = !base::subtle::Acquire_Load(&reading_);
-    int index = !base::subtle::Acquire_Load(&slots_[towrite]);
-    states_[towrite][index] = state;
-    base::subtle::MemoryBarrier();
-    base::subtle::Acquire_Store(&slots_[towrite], index);
-    base::subtle::Acquire_Store(&latest_, towrite);
-  }
-
-  // Attempt to update the state, updating only if the generation counter is
-  // newer.
-  void Read(T* state) {
-    base::subtle::MemoryBarrier();
-    int toread = !!base::subtle::Acquire_Load(&latest_);
-    base::subtle::Acquire_Store(&reading_, toread);
-    int index = !!base::subtle::Acquire_Load(&slots_[toread]);
-    if (states_[toread][index].generation - state->generation < 0x80000000U)
-      *state = states_[toread][index];
-  }
-};
-
-typedef SharedState<CommandBuffer::State> CommandBufferSharedState;
-
-}  // namespace gpu
-
-#endif  // GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_
diff --git a/gpu/command_buffer/common/command_buffer_shared_test.cc b/gpu/command_buffer/common/command_buffer_shared_test.cc
deleted file mode 100644
index f7ff2f0..0000000
--- a/gpu/command_buffer/common/command_buffer_shared_test.cc
+++ /dev/null
@@ -1,97 +0,0 @@
-
-// Copyright (c) 2012 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.
-
-// This file contains the tests for the CommandBufferSharedState class.
-
-#include "gpu/command_buffer/common/command_buffer_shared.h"
-#include "base/bind.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/threading/thread.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace gpu {
-
-class CommandBufferSharedTest : public testing::Test {
- protected:
-
-  virtual void SetUp() {
-    shared_state_.reset(new CommandBufferSharedState());
-    shared_state_->Initialize();
-  }
-
-  scoped_ptr<CommandBufferSharedState> shared_state_;
-};
-
-TEST_F(CommandBufferSharedTest, TestBasic) {
-  CommandBuffer::State state;
-
-  shared_state_->Read(&state);
-
-  EXPECT_LT(state.generation, 0x80000000);
-  EXPECT_EQ(state.get_offset, 0);
-  EXPECT_EQ(state.put_offset, 0);
-  EXPECT_EQ(state.token, -1);
-  EXPECT_EQ(state.error, gpu::error::kNoError);
-  EXPECT_EQ(state.context_lost_reason, gpu::error::kUnknown);
-}
-
-static const int kSize = 100000;
-
-void WriteToState(int32 *buffer,
-                  CommandBufferSharedState* shared_state) {
-  CommandBuffer::State state;
-  for (int i = 0; i < kSize; i++) {
-    state.token = i - 1;
-    state.get_offset = i + 1;
-    state.generation = i + 2;
-    state.error = static_cast<gpu::error::Error>(i + 3);
-    // Ensure that the producer doesn't update the buffer until after the
-    // consumer reads from it.
-    EXPECT_EQ(buffer[i], 0);
-
-    shared_state->Write(state);
-  }
-}
-
-TEST_F(CommandBufferSharedTest, TestConsistency) {
-  scoped_array<int32> buffer;
-  buffer.reset(new int32[kSize]);
-  base::Thread consumer("Reader Thread");
-
-  memset(buffer.get(), 0, kSize * sizeof(int32));
-
-  consumer.Start();
-  consumer.message_loop()->PostTask(
-      FROM_HERE, base::Bind(&WriteToState, buffer.get(),
-                            shared_state_.get()));
-
-  CommandBuffer::State last_state;
-  while (1) {
-    CommandBuffer::State state = last_state;
-
-    shared_state_->Read(&state);
-
-    if (state.generation < last_state.generation)
-      continue;
-
-    if (state.get_offset >= 1) {
-      buffer[state.get_offset - 1] = 1;
-      // Check that the state is consistent
-      EXPECT_LE(last_state.token, state.token);
-      EXPECT_LE(last_state.generation, state.generation);
-      last_state = state;
-      EXPECT_EQ(state.token, state.get_offset - 2);
-      EXPECT_EQ(state.generation,
-                static_cast<unsigned int>(state.get_offset) + 1);
-      EXPECT_EQ(state.error, state.get_offset + 2);
-
-      if (state.get_offset == kSize)
-        break;
-    }
-  }
-}
-
-}  // namespace gpu
-
diff --git a/gpu/command_buffer/service/command_buffer_service.cc b/gpu/command_buffer/service/command_buffer_service.cc
index 13d3098..c5a1162 100644
--- a/gpu/command_buffer/service/command_buffer_service.cc
+++ b/gpu/command_buffer/service/command_buffer_service.cc
@@ -9,7 +9,6 @@
 #include "base/process_util.h"
 #include "base/debug/trace_event.h"
 #include "gpu/command_buffer/common/cmd_buffer_common.h"
-#include "gpu/command_buffer/common/command_buffer_shared.h"
 
 using ::base::SharedMemory;
 
@@ -17,7 +16,6 @@ namespace gpu {
 
 CommandBufferService::CommandBufferService()
     : ring_buffer_id_(-1),
-      shared_state_(NULL),
       num_entries_(0),
       get_offset_(0),
       put_offset_(0),
@@ -61,13 +59,6 @@ CommandBufferService::State CommandBufferService::GetLastState() {
   return GetState();
 }
 
-void CommandBufferService::UpdateState() {
-  if (shared_state_) {
-    CommandBufferService::State state = GetState();
-    shared_state_->Write(state);
-  }
-}
-
 CommandBufferService::State CommandBufferService::FlushSync(
     int32 put_offset, int32 last_known_get) {
   if (put_offset < 0 || put_offset > num_entries_) {
@@ -107,15 +98,6 @@ void CommandBufferService::SetGetBuffer(int32 transfer_buffer_id) {
   if (!get_buffer_change_callback_.is_null()) {
     get_buffer_change_callback_.Run(ring_buffer_id_);
   }
-
-  UpdateState();
-}
-
-void CommandBufferService::SetSharedStateBuffer(int32 transfer_buffer_id) {
-  gpu::Buffer buffer = GetTransferBuffer(transfer_buffer_id);
-  shared_state_ = reinterpret_cast<CommandBufferSharedState*>(buffer.ptr);
-
-  UpdateState();
 }
 
 void CommandBufferService::SetGetOffset(int32 get_offset) {
diff --git a/gpu/command_buffer/service/command_buffer_service.h b/gpu/command_buffer/service/command_buffer_service.h
index 2c59678..7704636 100644
--- a/gpu/command_buffer/service/command_buffer_service.h
+++ b/gpu/command_buffer/service/command_buffer_service.h
@@ -13,7 +13,6 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "gpu/command_buffer/common/command_buffer.h"
-#include "gpu/command_buffer/common/command_buffer_shared.h"
 
 namespace gpu {
 
@@ -57,16 +56,9 @@ class CommandBufferService : public CommandBuffer {
       const GetBufferChangedCallback& callback);
   virtual void SetParseErrorCallback(const base::Closure& callback);
 
-  // Setup the transfer buffer that shared state should be copied into.
-  void SetSharedStateBuffer(int32 transfer_buffer_id);
-
-  // Copy the current state into the shared state transfer buffer.
-  void UpdateState();
-
  private:
   int32 ring_buffer_id_;
   Buffer ring_buffer_;
-  CommandBufferSharedState* shared_state_;
   int32 num_entries_;
   int32 get_offset_;
   int32 put_offset_;
diff --git a/gpu/gpu.gyp b/gpu/gpu.gyp
index 7af8343..c24c4d1 100644
--- a/gpu/gpu.gyp
+++ b/gpu/gpu.gyp
@@ -317,7 +317,6 @@
         'command_buffer/common/bitfield_helpers_test.cc',
         'command_buffer/common/command_buffer_mock.cc',
         'command_buffer/common/command_buffer_mock.h',
-        'command_buffer/common/command_buffer_shared_test.cc',
         'command_buffer/common/gles2_cmd_format_test.cc',
         'command_buffer/common/gles2_cmd_format_test_autogen.h',
         'command_buffer/common/gles2_cmd_utils_unittest.cc',