CyclicBarrier LockSupport学习

学习CyclicBarrier可以了解下LockSupport

主要是这个方法

/**
 * Disables the current thread for thread scheduling purposes unless the
 * permit is available.
 *
 * <p>If the permit is available then it is consumed and the call
 * returns immediately; otherwise the current thread becomes disabled
 * for thread scheduling purposes and lies dormant until one of three
 * things happens:
 *
 * <ul>
 *
 * <li>Some other thread invokes {@link #unpark unpark} with the
 * current thread as the target; or
 *
 * <li>Some other thread {@linkplain Thread#interrupt interrupts}
 * the current thread; or
 *
 * <li>The call spuriously (that is, for no reason) returns.
 * </ul>
 *
 * <p>This method does <em>not</em> report which of these caused the
 * method to return. Callers should re-check the conditions which caused
 * the thread to park in the first place. Callers may also determine,
 * for example, the interrupt status of the thread upon return.
 */
public static void park() {
    unsafe.park(false, 0L);
}

/**
 * Makes available the permit for the given thread, if it
 * was not already available.  If the thread was blocked on
 * {@code park} then it will unblock.  Otherwise, its next call
 * to {@code park} is guaranteed not to block. This operation
 * is not guaranteed to have any effect at all if the given
 * thread has not been started.
 *
 * @param thread the thread to unpark, or {@code null}, in which case
 *        this operation has no effect
 */
public static void unpark(Thread thread) {
    if (thread != null)
        unsafe.unpark(thread);
}

 

然后就是

/** The lock for guarding barrier entry */
private final ReentrantLock lock = new ReentrantLock();
/** Condition to wait on until tripped */
private final Condition trip = lock.newCondition();

/**
 * Implements interruptible condition wait.
 * <ol>
 * <li> If current thread is interrupted, throw InterruptedException.
 * <li> Save lock state returned by {@link #getState}.
 * <li> Invoke {@link #release} with
 *      saved state as argument, throwing
 *      IllegalMonitorStateException if it fails.
 * <li> Block until signalled or interrupted.
 * <li> Reacquire by invoking specialized version of
 *      {@link #acquire} with saved state as argument.
 * <li> If interrupted while blocked in step 4, throw InterruptedException.
 * </ol>
 */
public final void await() throws InterruptedException {
    if (Thread.interrupted())
        throw new InterruptedException();
    Node node = addConditionWaiter();
    long savedState = fullyRelease(node);
    int interruptMode = 0;
    while (!isOnSyncQueue(node)) {
        LockSupport.park(this);
        if ((interruptMode = checkInterruptWhileWaiting(node)) != 0)
            break;
    }
    if (acquireQueued(node, savedState) && interruptMode != THROW_IE)
        interruptMode = REINTERRUPT;
    if (node.nextWaiter != null) // clean up if cancelled
        unlinkCancelledWaiters();
    if (interruptMode != 0)
        reportInterruptAfterWait(interruptMode);
}