[release/9.0-staging] [Profiler] Avoid Recursive ThreadStoreLock in Profiling Thread Enumerator #110665
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Profiling Enumerators look to acquire the ThreadStoreLock. In release config, re-acquiring the ThreadStoreLock and releasing it in ProfilerThreadEnum::Init will cause problems if the callback invoking EnumThread has logic that depends on the ThreadStoreLock being held. To avoid recursively acquiring the ThreadStoreLock, expand the condition when the profiling thread enumerator shouldn't acquire the ThreadStoreLock.
There was a potential race condition when setting the flag before suspending and resetting the flag after restarting. For example, if the thread restarting runtime is preempted right after resuming runtime, the flag could remain unset by the time another thread looks to suspend runtime, which would see that the flag as set.
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Tagging subscribers to this area: @tommcdon |
tommcdon
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Dec 17, 2024
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Backport of #110548 to release/9.0-staging
/cc @mdh1418
Customer Impact
#110062
Profiler users invoking
EnumThreadswithin aRuntimeSuspendFinishedcallback will cause an infinite wait because theEnumThreadswill recursively acquire/release the ThreadStore lock.Regression
This did not occur in .NET 8.0. The recursive ThreadStoreLock acquire/release was always there, but the condition that previously prevented this case causing an infinite wait was removed in #101782
Testing
The issue was reproduced locally and the fix was confirmed locally.
The issue was missed previously because there were no profiler tests covering this edge-case scenario. It is hard to cover all the ways our customers will use Profiler APIs.
A runtime test was added for this particular scenario, invoking the
EnumThreadsAPI within aRuntimeSuspendFinishedcallback.Risk
Low. The changes only affect Profiler users that specifically invoke
EnumThreadswithin aRuntimeSuspendFinishedcallback and trigger a GC.IMPORTANT: If this backport is for a servicing release, please verify that:
release/X.0-staging, notrelease/X.0.Package authoring no longer needed in .NET 9
IMPORTANT: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version.
Keep in mind that we still need package authoring in .NET 8 and older versions.