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[3.14] gh-132917: fix data race on last_mem in free-threading gc (GH-134692) #134802

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Merged
merged 1 commit into from
May 27, 2025
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[3.14] gh-132917: fix data race on last_mem in free-threading gc (GH-134692) #134802

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5 changes: 3 additions & 2 deletions Python/gc_free_threading.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2062,7 +2062,7 @@ gc_should_collect_mem_usage(GCState *gcstate)
// 70,000 new container objects.
return true;
}
Py_ssize_t last_mem = gcstate->last_mem;
Py_ssize_t last_mem = _Py_atomic_load_ssize_relaxed(&gcstate->last_mem);
Py_ssize_t mem_threshold = Py_MAX(last_mem / 10, 128);
if ((mem - last_mem) > mem_threshold) {
// The process memory usage has increased too much, do a collection.
Expand Down Expand Up @@ -2245,7 +2245,8 @@ gc_collect_internal(PyInterpreterState *interp, struct collection_state *state,

// Store the current memory usage, can be smaller now if breaking cycles
// freed some memory.
state->gcstate->last_mem = get_process_mem_usage();
Py_ssize_t last_mem = get_process_mem_usage();
_Py_atomic_store_ssize_relaxed(&state->gcstate->last_mem, last_mem);

// Append objects with legacy finalizers to the "gc.garbage" list.
handle_legacy_finalizers(state);
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