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gh-141510: Avoid critical section on frozendict copy #145920

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gh-141510: Avoid critical section on frozendict copy #145920

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836ad73
gh-141510: Avoid critical section on frozendict copy
vstinner Mar 5, 2026
02fe87f
Fix assertion in clone_combined_dict_keys()
vstinner Mar 13, 2026
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31 changes: 23 additions & 8 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -968,7 +968,9 @@ clone_combined_dict_keys(PyDictObject *orig)
assert(orig->ma_keys != Py_EMPTY_KEYS);
assert(orig->ma_keys->dk_refcnt == 1);

ASSERT_DICT_LOCKED(orig);
if (!PyFrozenDict_Check(orig)) {
ASSERT_DICT_LOCKED(orig);
}

size_t keys_size = _PyDict_KeysSize(orig->ma_keys);
PyDictKeysObject *keys = PyMem_Malloc(keys_size);
Expand Down Expand Up @@ -4322,7 +4324,10 @@ copy_lock_held(PyObject *o, int as_frozendict)
PyObject *copy;
PyDictObject *mp;

ASSERT_DICT_LOCKED(o);
// frozendict is immutable and so doesn't need critical section
if (!PyFrozenDict_Check(o)) {
ASSERT_DICT_LOCKED(o);
}

mp = (PyDictObject *)o;
if (mp->ma_used == 0) {
Expand Down Expand Up @@ -4445,9 +4450,14 @@ anydict_copy(PyObject *o)
assert(PyAnyDict_Check(o));

PyObject *res;
Py_BEGIN_CRITICAL_SECTION(o);
res = copy_lock_held(o, PyFrozenDict_Check(o));
Py_END_CRITICAL_SECTION();
if (PyFrozenDict_Check(o)) {
res = copy_lock_held(o, 1);
}
else {
Py_BEGIN_CRITICAL_SECTION(o);
res = copy_lock_held(o, 0);
Py_END_CRITICAL_SECTION();
}
return res;
}

Expand All @@ -4459,9 +4469,14 @@ _PyDict_CopyAsDict(PyObject *o)
assert(PyAnyDict_Check(o));

PyObject *res;
Py_BEGIN_CRITICAL_SECTION(o);
res = copy_lock_held(o, 0);
Py_END_CRITICAL_SECTION();
if (PyFrozenDict_Check(o)) {
res = copy_lock_held(o, 0);
}
else {
Py_BEGIN_CRITICAL_SECTION(o);
res = copy_lock_held(o, 0);
Py_END_CRITICAL_SECTION();
}
return res;
}

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