concurrent-7-AQS-CountDownLatch，CyclicBarrier

CountDownLatch

CountDownLatch#tryAcquireShared

   protected int tryAcquireShared(int acquires) {            return (getState() == 0) ? 1 : -1;   //获取状态是不是达到条件        }

CountDownLatch#tryReleaseShared

protected boolean tryReleaseShared(int releases) {            // Decrement count; signal when transition to zero            for (;;) {                int c = getState();  //获取状态                if (c == 0)     //表示已达到条件                    return false;                int nextc = c-1;                if (compareAndSetState(c, nextc))  //循环cas操作释放资源                    return nextc == 0; //如果为true 需要唤醒等待的await节点            }        }

CyclicBarrier

CyclicBarrier#dowait

private int dowait(boolean timed, long nanos)        throws InterruptedException, BrokenBarrierException,               TimeoutException {        final ReentrantLock lock = this.lock;        lock.lock();        try {            final Generation g = generation;            if (g.broken)                throw new BrokenBarrierException();            if (Thread.interrupted()) {                breakBarrier();   //唤醒条件等待队列，设置broken = true  重置资源数量                throw new InterruptedException();            }            int index = --count;    //如果为0，则开启栅栏            if (index == 0) {  // tripped                boolean ranAction = false;                try {                    final Runnable command = barrierCommand;                    if (command != null)                        command.run();   //执行栅栏开启后的方法                    ranAction = true;                    nextGeneration();   //开启下一个栅栏循环                    return 0;                } finally {                    if (!ranAction)   //如果失败重置                        breakBarrier();                }            }            //如果index ＞０　            // loop until tripped, broken, interrupted, or timed out            for (;;) {                try {                    if (!timed)  //如果没有时间限制则一直等待被唤醒                        trip.await();                    else if (nanos > 0L)                        nanos = trip.awaitNanos(nanos);                } catch (InterruptedException ie) {                    if (g == generation && ! g.broken) {                        breakBarrier();                        throw ie;                    } else {                        // We're about to finish waiting even if we had not                        // been interrupted, so this interrupt is deemed to                        // "belong" to subsequent execution.                        Thread.currentThread().interrupt();                    }                }                if (g.broken)                    throw new BrokenBarrierException();                if (g != generation)  //开启了下一个栅栏则return                    return index;                if (timed && nanos <= 0L) {  //超过了时间限制，则抛出异常                    breakBarrier();                    throw new TimeoutException();                }            }        } finally {            lock.unlock();        }    }