XiaoyiPeng removed a comment on pull request #3509:
URL: https://github.com/apache/rocketmq/pull/3509#issuecomment-995780683
> Hi, @areyouok @RongtongJin @duhenglucky
>
> I reviewed the given test cases again, the broker will never hangs in your
test, @areyouok
>
> In your test case, the reason you made the judgment: **broker hangs**, is
due to your console println "begin scan, i still alive", but not println
"finish scan, i still alive" finally, or vice versa.
>
> **That's because the IDE console lied to us！** **Our naked eyes do not
perceive the tiny change in the console !**
>
> You can use `AtomicInteger` to print the times of prints before you print
"begin scan, i still alive" and "finish scan, i still alive". The code shown
below:
>
> ```java
> public class TestLinkedBlockingQueue {
> public static void main(String[] args) throws InterruptedException {
> AtomicInteger startScanTimes = new AtomicInteger();
> AtomicInteger finishScanTimes = new AtomicInteger();
> LinkedBlockingQueue<Object> queue = new LinkedBlockingQueue<>();
> for (int i = 0; i < 10; i++) {
> new Thread(() -> {
> while (true) {
> queue.offer(new Object());
> queue.remove();
> }
> }).start();
> }
>
> while (true) {
> System.out.println("begin scan, i still alive, times: " +
startScanTimes.incrementAndGet());
> queue.stream().filter(o -> o != null)
> .findFirst().isPresent();
> Thread.sleep(1000);
> System.out.println("finish scan, i still alive, times: " +
finishScanTimes.incrementAndGet());
> }
> }
> }
> ```
>
> **We can run a fatigue test with this test case, it will never hangs and
print the given info forever!**
>
> As for the **potential deadlock**, that was my initial misjudgment. In
methods of class `LinkedBlockingQueue`, `putLock` and `takeLock` are never
acquired simultaneously in a different order.
>
> best regards!
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