Barrier.h revision be48137beb68893870c26b7f8c59eac5d0bf517a 
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
24namespace android {
25
26class Barrier
27{
28public:
29    inline Barrier() : state(CLOSED) { }
30    inline ~Barrier() { }
31    void open() {
32        // gcc memory barrier, this makes sure all memory writes
33        // have been issued by gcc. On an SMP system we'd need a real
34        // h/w barrier.
35        asm volatile ("":::"memory");
36        Mutex::Autolock _l(lock);
37        state = OPENED;
38        cv.broadcast();
39    }
40    void close() {
41        Mutex::Autolock _l(lock);
42        state = CLOSED;
43    }
44    void wait() const {
45        Mutex::Autolock _l(lock);
46        while (state == CLOSED) {
47            cv.wait(lock);
48        }
49    }
50private:
51    enum { OPENED, CLOSED };
52    mutable     Mutex       lock;
53    mutable     Condition   cv;
54    volatile    int         state;
55};
56
57}; // namespace android
58
59#endif // ANDROID_BARRIER_H
60