我看了一下JDK的LinkedBlockingQueue
类,感到很困惑。
public void put(E e) throws InterruptedException {
if (e == null) throw new NullPointerException();
// Note: convention in all put/take/etc is to preset local var
// holding count negative to indicate failure unless set.
int c = -1;
final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count;
putLock.lockInterruptibly();
try {
/*
* Note that count is used in wait guard even though it is
* not protected by lock. This works because count can
* only decrease at this point (all other puts are shut
* out by lock), and we (or some other waiting put) are
* signalled if it ever changes from
* capacity. Similarly for all other uses of count in
* other wait guards.
*/
while (count.get() == capacity) {
notFull.await();
}
enqueue(e);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
}
请看最后一个条件(c == 0),我认为应该是(c != 0)。
谢谢,我明白了。但我有另一个问题关于LinkedBlockingQueue的实现。enqueue和dequeue函数不能相互干扰。我发现当put()被执行时,take()也可以被执行。而head和tail对象没有同步,因此在不同线程中,enqueue和dequeue可以同时工作。这不是线程安全的,可能会导致故障。
while (count.get() == 0) notEmpty.await();
在take中。 - bestsss