XiaoyiPeng edited a comment on pull request #3509:
URL: https://github.com/apache/rocketmq/pull/3509#issuecomment-995634452
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.
Meanwhile, the author of class LinkedBlockingQueue is **Doug Lea**, I don't
think their test team would be so lax.
best regards!
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