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gh-129069: Fix listobject.c data races due to memmove #142957

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Merged
colesbury merged 4 commits into from
Dec 19, 2025
Merged

gh-129069: Fix listobject.c data races due to memmove #142957

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97e8d13
gh-129069: Fix listobject.c data races due to memmove
colesbury Dec 17, 2025
11c64a6
Add _Py_IsOwnedByCurrentThread() special case for list_atomic_memmove
colesbury Dec 19, 2025
44226b4
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colesbury Dec 19, 2025
761cad1
Merge branch 'main' into gh-129069-list-memmove
colesbury Dec 19, 2025
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Add _Py_IsOwnedByCurrentThread() special case for list_atomic_memmove
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@colesbury
colesbury committed Dec 19, 2025
commit 11c64a682e2601afffc64fdda3bc9681e85b4394
6 changes: 6 additions & 0 deletions Objects/listobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -896,6 +896,12 @@ list_atomic_memmove(PyListObject *a, PyObject **dest, PyObject **src, Py_ssize_t
#ifndef Py_GIL_DISABLED
memmove(dest, src, n * sizeof(PyObject *));
#else
_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
if (_Py_IsOwnedByCurrentThread((PyObject *)a) && !_PyObject_GC_IS_SHARED(a)) {
// No other threads can read this list concurrently
memmove(dest, src, n * sizeof(PyObject *));
return;
}
if (dest < src) {
for (Py_ssize_t i = 0; i != n; i++) {
_Py_atomic_store_ptr_release(&dest[i], src[i]);
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