XiaoyiPeng commented on pull request #3509:
URL: https://github.com/apache/rocketmq/pull/3509#issuecomment-991684075
> This commit cause critical problem. we should rollback it. And I sugguest
review PR #3540 again.
>
Thanks for your review. @areyouok , @RongtongJin
I know the reason. This is a potential **Lock Ordering Deadlock** caused by
`putLock` and `takeLock` of `LinkedBlockingQueue`
The method `offer()` will grab the `LinkedBlockingQueue#putLock` and method
`remove()` will grab the `LinkedBlockingQueue#takeLock` .
Meanwhile, in this PR, stream operation of `LinkedBlockingQueue` will
invoking `LinkedBlockingQueue#fullyLock()` method in
`LinkedBlockingQueue$LBQSpliterator#tryAdvance()` as shown below:
```java
public boolean tryAdvance(Consumer<? super E> action) {
if (action == null) throw new NullPointerException();
final LinkedBlockingQueue<E> q = this.queue;
if (!exhausted) {
E e = null;
q.fullyLock();
try {
if (current == null)
current = q.head.next;
while (current != null) {
e = current.item;
current = current.next;
if (e != null)
break;
}
} finally {
q.fullyUnlock();
}
if (current == null)
exhausted = true;
if (e != null) {
action.accept(e);
return true;
}
}
return false;
}
```
I will fix it!
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