[Issue 7168][C++] Fix pattern consumer's deadlock for topics auto discovery #7206
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Fixes #7168
Motivation
When a pattern consumer is blocked by
receive()
, themutex_
will be held until new messages arrived. If the auto discovery timer task found new topics and tried to subscribe them,mutex_
must be acquired first, then the deadlock happened.Modifications
mutex_
after the consumer's state was verified.receive(Message&)
orreceive(Message&, int)
methods.Verifying this change
This change is already covered by existing tests, such as BasicEndToEndTest.testPatternMultiTopicsConsumerAutoDiscovery.