Fix EventSource shutdown deadlock #56453
Merged
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Fixes #48342
A deadlock was occuring because we held the EventListenersLock
while calling into EventUnregister which will take ETW's own native
lock. In the case of ETW sending an enable/disable notification
these locks are taken in reverse order which triggers a deadlock.
The fix is to ensure that we always order the locks so that any code
path taking both locks always takes the ETW lock first. In this case
it meant accumulating the list of event sources to dispose under
the lock but then exiting the lock prior to calling Dispose() which
will eventually call EventUnregister.