15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Copyright (c) 2012 The Chromium Authors. All rights reserved. 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// found in the LICENSE file. 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#ifndef GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_ 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#define GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_ 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "command_buffer.h" 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "base/atomicops.h" 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)namespace gpu { 125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This is a standard 4-slot asynchronous communication mechanism, used to 145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// ensure that the reader gets a consistent copy of what the writer wrote. 155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template<typename T> 165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)class SharedState { 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) T states_[2][2]; 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::Atomic32 reading_; 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::Atomic32 latest_; 205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::Atomic32 slots_[2]; 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)public: 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void Initialize() { 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (int i = 0; i < 2; ++i) { 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (int j = 0; j < 2; ++j) { 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) states_[i][j] = T(); 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::NoBarrier_Store(&reading_, 0); 315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::NoBarrier_Store(&latest_, 0); 325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::NoBarrier_Store(&slots_[0], 0); 332a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) base::subtle::Release_Store(&slots_[1], 0); 342a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) base::subtle::MemoryBarrier(); 355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void Write(const T& state) { 385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) int towrite = !base::subtle::Acquire_Load(&reading_); 395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) int index = !base::subtle::Acquire_Load(&slots_[towrite]); 405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) states_[towrite][index] = state; 412a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) base::subtle::Release_Store(&slots_[towrite], index); 422a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) base::subtle::Release_Store(&latest_, towrite); 435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::MemoryBarrier(); 445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Attempt to update the state, updating only if the generation counter is 475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // newer. 485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void Read(T* state) { 495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) base::subtle::MemoryBarrier(); 505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) int toread = !!base::subtle::Acquire_Load(&latest_); 512a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) base::subtle::Release_Store(&reading_, toread); 522a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) base::subtle::MemoryBarrier(); 535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) int index = !!base::subtle::Acquire_Load(&slots_[toread]); 545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (states_[toread][index].generation - state->generation < 0x80000000U) 555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *state = states_[toread][index]; 565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)typedef SharedState<CommandBuffer::State> CommandBufferSharedState; 605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} // namespace gpu 625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#endif // GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_ 64