15c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten/* 25c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * Copyright (C) 2012 The Android Open Source Project 35c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * 45c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * Licensed under the Apache License, Version 2.0 (the "License"); 55c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * you may not use this file except in compliance with the License. 65c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * You may obtain a copy of the License at 75c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * 85c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * http://www.apache.org/licenses/LICENSE-2.0 95c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * 105c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * Unless required by applicable law or agreed to in writing, software 115c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * distributed under the License is distributed on an "AS IS" BASIS, 125c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 135c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * See the License for the specific language governing permissions and 145c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten * limitations under the License. 155c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten */ 165c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 175c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#include <new> 185c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#include <cutils/atomic.h> 195c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#include <cutils/atomic-inline.h> // for android_memory_barrier() 205c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#include <media/SingleStateQueue.h> 215c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 225c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastennamespace android { 235c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 245c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> SingleStateQueue<T>::Mutator::Mutator(Shared *shared) 255c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten : mSequence(0), mShared((Shared *) shared) 265c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 275c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten // exactly one of Mutator and Observer must initialize, currently it is Observer 285c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten //shared->init(); 295c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 305c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 315c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> int32_t SingleStateQueue<T>::Mutator::push(const T& value) 325c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 335c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten Shared *shared = mShared; 345c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten int32_t sequence = mSequence; 355c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten sequence++; 365c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten android_atomic_acquire_store(sequence, &shared->mSequence); 375c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten shared->mValue = value; 385c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten sequence++; 395c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten android_atomic_release_store(sequence, &shared->mSequence); 405c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten mSequence = sequence; 415c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten // consider signalling a futex here, if we know that observer is waiting 425c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return sequence; 435c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 445c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 455c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> bool SingleStateQueue<T>::Mutator::ack() 465c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 475c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return mShared->mAck - mSequence == 0; 485c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 495c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 505c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> bool SingleStateQueue<T>::Mutator::ack(int32_t sequence) 515c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 525c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten // this relies on 2's complement rollover to detect an ancient sequence number 535c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return mShared->mAck - sequence >= 0; 545c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 555c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 565c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> SingleStateQueue<T>::Observer::Observer(Shared *shared) 575c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten : mSequence(0), mSeed(1), mShared((Shared *) shared) 585c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 595c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten // exactly one of Mutator and Observer must initialize, currently it is Observer 605c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten shared->init(); 615c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 625c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 635c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> bool SingleStateQueue<T>::Observer::poll(T& value) 645c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 655c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten Shared *shared = mShared; 665c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten int32_t before = shared->mSequence; 675c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten if (before == mSequence) { 685c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return false; 695c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } 705c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten for (int tries = 0; ; ) { 715c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten const int MAX_TRIES = 5; 725c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten if (before & 1) { 735c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten if (++tries >= MAX_TRIES) { 745c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return false; 755c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } 765c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten before = shared->mSequence; 775c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } else { 785c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten android_memory_barrier(); 795c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten T temp = shared->mValue; 805c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten int32_t after = android_atomic_release_load(&shared->mSequence); 815c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten if (after == before) { 825c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten value = temp; 835c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten shared->mAck = before; 845c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten mSequence = before; 855c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return true; 865c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } 875c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten if (++tries >= MAX_TRIES) { 885c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten return false; 895c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } 905c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten before = after; 915c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } 925c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten } 935c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 945c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 955c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#if 0 965c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kastentemplate<typename T> SingleStateQueue<T>::SingleStateQueue(void /*Shared*/ *shared) 975c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten{ 985c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten ((Shared *) shared)->init(); 995c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} 1005c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#endif 1015c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 1025c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten} // namespace android 1035c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten 1045c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten// hack for gcc 1055c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#ifdef SINGLE_STATE_QUEUE_INSTANTIATIONS 1065c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#include SINGLE_STATE_QUEUE_INSTANTIATIONS 1075c4cc0d99d3b1cb35c5d7c237272ee53142745fbGlenn Kasten#endif 108