gh-151646: Fix data race between gc.get_stats() and GC in free-threading builds#151766
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zangjiucheng wants to merge 1 commit into
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gh-151646: Fix data race between gc.get_stats() and GC in free-threading builds#151766zangjiucheng wants to merge 1 commit into
zangjiucheng wants to merge 1 commit into
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In free-threading builds,
gc_get_stats_impl()reads per-generation statswith plain struct copies while
gc_collect_main()writes the same fieldsafter
_Py_StartTheWorld()— no synchronisation on either side.Fix: add
PyMutex stats_mutexto_gc_runtime_state(underPy_GIL_DISABLED) and hold it around both the seven field writes in thewriter and the three struct copies in the reader. The lock is acquired after
_Py_StartTheWorld(), so no deadlock with stop-the-world. GIL build isunchanged.
Also adds
Lib/test/test_free_threading/test_gc_get_stats_race.py.Verified with TSAN on Linux: race confirmed on
main, clean on the patch.🤖 Generated with Claude Code
gc.get_stats()and a concurrent collection under free-threading #151646