The Android Open Source Project | edbf3b6 | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 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() { } |
Jesse Hall | c615767 | 2014-07-13 12:47:02 -0700 | [diff] [blame] | 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. |
The Android Open Source Project | edbf3b6 | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 35 | void open() { |
The Android Open Source Project | edbf3b6 | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 36 | Mutex::Autolock _l(lock); |
| 37 | state = OPENED; |
| 38 | cv.broadcast(); |
| 39 | } |
Jesse Hall | c615767 | 2014-07-13 12:47:02 -0700 | [diff] [blame] | 40 | |
| 41 | // Reset the Barrier, so wait() will block until open() has been called. |
The Android Open Source Project | edbf3b6 | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 42 | void close() { |
| 43 | Mutex::Autolock _l(lock); |
| 44 | state = CLOSED; |
| 45 | } |
Jesse Hall | c615767 | 2014-07-13 12:47:02 -0700 | [diff] [blame] | 46 | |
| 47 | // Wait until the Barrier is OPEN. |
| 48 | // Provides acquire semantics: no subsequent loads or stores will occur |
| 49 | // until wait() returns. |
The Android Open Source Project | edbf3b6 | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 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 |