codelipenghui commented on a change in pull request #12654:
URL: https://github.com/apache/pulsar/pull/12654#discussion_r744478204
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File path:
pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java
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@@ -474,7 +475,13 @@ public void registerListener(TopicName topicName,
TopicPolicyListener<TopicPolic
@Override
public void unregisterListener(TopicName topicName,
TopicPolicyListener<TopicPolicies> listener) {
- listeners.computeIfAbsent(topicName, k ->
Lists.newCopyOnWriteArrayList()).remove(listener);
Review comment:
It should be a problem if thread A reaches line 478 first, then thread B
reaches line 473 and then add a listener. After that, thread A continues to
remove the listener, finally, the added listener will be removed, but actually,
the `unregisterListener` operation happens first, we will get unexpected
behavior.
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