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Deadlock in loader lock (CoreCLR) from background GC in XAML apps #114182
Description
Description
We're hitting random hangs in the Microsoft Store in debug builds on CoreCLR.
Context from @hoyosjs:
"This is a loader lock deadlock
[...]
- Thread 3 tries to do a GC from the added pressure, which tries to start the background GC thread.
- BG thread (and a ton of others) fail to start - they are stuck in LdrpInitializeThread on LdrpAcquireLoaderLock
- They can't start bc thread 16 has the lock (LdrShutdownThread) and it's doing TLS destruction. Part of it must happen in COOP GC. Transitioning to coop means it waits for the original GC...
Crash dump (MSFT only): loader_hang_dmp.zip
Reproduction Steps
It just happens when using the app for a while.
Configuration
- .NET 9.0.202
Activity
jkotas commentedon Apr 3, 2025
Duplicate of #110350 . cc @VSadov
jkotas commentedon Apr 3, 2025
@Sergio0694 Could you please validate that it is fixed in 9.0.5?
(backport PR #113055)
Sergio0694 commentedon Apr 3, 2025
Oh that's nice! I can try, yes, though it might be slightly tricky as I can't repro this myself.
Just to confirm, is this only affecting CoreCLR, or does this affect Native AOT as well?
VSadov commentedon Apr 3, 2025
Yes, this looks like #110350 . The fix has been backported to 9.0, but may not be available till the next servicing release.
As Jan suggested - it would be very helpful if you could try with 9.0.5 bits (i.e. #113055)
jkotas commentedon Apr 3, 2025
It does not affect Native AOT. The fix was to switch regular CoreCLR to how Native AOT works.
Sergio0694 commentedon Apr 3, 2025
Perfect, thank you for confirming! At least we know this only affects our dev inner loop then 🙂
VSadov commentedon Apr 3, 2025
NativeAOT had a remotely related issue, fixed in #113194
But that is related to COM and is pretty hard to observe, even intentionally.
It would not show up as a deadlock though. In fact, in most cases it would not have any adverse effects, so is unlikely to bother you.
Sergio0694 commentedon Apr 7, 2025
I assume I can test the fix by installing the latest nightly SDK from the 9.0 branch from the SDK repo?
jkotas commentedon Apr 7, 2025
Yes, you can do that if you do not want to wait for official release.
dotnet-policy-service commentedon Apr 7, 2025
This issue has been marked
needs-author-actionand may be missing some important information.dotnet-policy-service commentedon Apr 22, 2025
This issue has been automatically marked
no-recent-activitybecause it has not had any activity for 14 days. It will be closed if no further activity occurs within 14 more days. Any new comment (by anyone, not necessarily the author) will removeno-recent-activity.dotnet-policy-service commentedon May 6, 2025
This issue will now be closed since it had been marked
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