Fix EventSource shutdown deadlock #56453
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Fixes dotnet#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.
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Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti Issue DetailsFixes #48342 A deadlock was occuring because we held the EventListenersLock The fix is to ensure that we always order the locks so that any code
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stephentoub
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Jul 28, 2021
src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventSource.cs
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josalem
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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.