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gh-142048: Fix lost allocations on thread cleanup #142233

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Merged
kumaraditya303 merged 2 commits into from
Dec 10, 2025
Merged

gh-142048: Fix lost allocations on thread cleanup #142233

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da77101
Fix lost allocations on thread cleanup
kevmo314 Dec 3, 2025
d361e77
Merge branch 'main' into fix-lost-allocations
kumaraditya303 Dec 10, 2025
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11 changes: 9 additions & 2 deletions Python/pystate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1765,16 +1765,23 @@ PyThreadState_Clear(PyThreadState *tstate)
struct _Py_freelists *freelists = _Py_freelists_GET();
_PyObject_ClearFreeLists(freelists, 1);

// Flush the thread's local GC allocation count to the global count
// before the thread state is cleared, otherwise the count is lost.
_PyThreadStateImpl *tstate_impl = (_PyThreadStateImpl *)tstate;
_Py_atomic_add_int(&tstate->interp->gc.young.count,
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@kevmo314 kevmo314 Dec 3, 2025

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Since this is less common perhaps it's ok to allow the global GC count to go negative here? The compare-and-exchange loop is more accurate though, I can update to use that if preferred.

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@colesbury colesbury Dec 4, 2025

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Yeah, I think going negative here is fine

(int)tstate_impl->gc.alloc_count);
tstate_impl->gc.alloc_count = 0;

// Merge our thread-local refcounts into the type's own refcount and
// free our local refcount array.
_PyObject_FinalizePerThreadRefcounts((_PyThreadStateImpl *)tstate);
_PyObject_FinalizePerThreadRefcounts(tstate_impl);

// Remove ourself from the biased reference counting table of threads.
_Py_brc_remove_thread(tstate);

// Release our thread-local copies of the bytecode for reuse by another
// thread
_Py_ClearTLBCIndex((_PyThreadStateImpl *)tstate);
_Py_ClearTLBCIndex(tstate_impl);
#endif

// Merge our queue of pointers to be freed into the interpreter queue.
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