[3.14] gh-137433: Fix deadlock with stop-the-world and daemon threads (gh-137735)#138965
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…ythongh-137735) There was a deadlock originally seen by Memray when a daemon thread enabled or disabled profiling while the interpreter was shutting down. I think this could also happen with garbage collection, but I haven't seen that in practice. The daemon thread could be hung while trying acquire the global rwmutex that prevents overlapping global and per-interpreter stop-the-world events. Since it already held the main interpreter's stop-the-world lock, it also deadlocked the main thread, which is trying to perform interpreter finalization. Swap the order of lock acquisition to prevent this deadlock. Additionally, refactor `_PyParkingLot_Park` so that the global buckets hashtable is left in a clean state if the thread is hung in `PyEval_AcquireThread`. (cherry picked from commit 90fe325) Co-authored-by: Sam Gross <colesbury@gmail.com>
This was referenced Sep 16, 2025
colesbury approved these changes Sep 16, 2025
ZeroIntensity approved these changes Sep 16, 2025
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Up to Hugo if he wants to include this in the RC.
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colesbury commented Sep 16, 2025
I think this can wait until 3.14.1 |
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colesbury commented Sep 16, 2025
The added test is failing because we'll need to merge: Before landing this PR to avoid an additional deadlock |
kumaraditya303 approved these changes Oct 7, 2025
encukou merged commit e09f33e into python:3.14 52 checks passed
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There was a deadlock originally seen by Memray when a daemon thread
enabled or disabled profiling while the interpreter was shutting down.
I think this could also happen with garbage collection, but I haven't
seen that in practice.
The daemon thread could be hung while trying acquire the global rwmutex
that prevents overlapping global and per-interpreter stop-the-world events.
Since it already held the main interpreter's stop-the-world lock, it
also deadlocked the main thread, which is trying to perform interpreter
finalization.
Swap the order of lock acquisition to prevent this deadlock.
Additionally, refactor
_PyParkingLot_Parkso that the global bucketshashtable is left in a clean state if the thread is hung in
PyEval_AcquireThread.(cherry picked from commit 90fe325)
Co-authored-by: Sam Gross colesbury@gmail.com