1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ANDROID_BARRIER_H 18 #define ANDROID_BARRIER_H 19 20 #include <stdint.h> 21 #include <sys/types.h> 22 #include <utils/threads.h> 23 24 namespace android { 25 26 class Barrier 27 { 28 public: 29 inline Barrier() : state(CLOSED) { } 30 inline ~Barrier() { } 31 32 // Release any threads waiting at the Barrier. 33 // Provides release semantics: preceding loads and stores will be visible 34 // to other threads before they wake up. 35 void open() { 36 Mutex::Autolock _l(lock); 37 state = OPENED; 38 cv.broadcast(); 39 } 40 41 // Reset the Barrier, so wait() will block until open() has been called. 42 void close() { 43 Mutex::Autolock _l(lock); 44 state = CLOSED; 45 } 46 47 // Wait until the Barrier is OPEN. 48 // Provides acquire semantics: no subsequent loads or stores will occur 49 // until wait() returns. 50 void wait() const { 51 Mutex::Autolock _l(lock); 52 while (state == CLOSED) { 53 cv.wait(lock); 54 } 55 } 56 private: 57 enum { OPENED, CLOSED }; 58 mutable Mutex lock; 59 mutable Condition cv; 60 volatile int state; 61 }; 62 63 }; // namespace android 64 65 #endif // ANDROID_BARRIER_H 66
