mirror of https://github.com/python/cpython
gh-117657: Fix TSan race in _PyDict_CheckConsistency (#121551)
The only remaining race in dictobject.c was in _PyDict_CheckConsistency when the dictionary has shared keys.
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@ -169,16 +169,15 @@ ASSERT_DICT_LOCKED(PyObject *op)
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#define STORE_INDEX(keys, size, idx, value) _Py_atomic_store_int##size##_relaxed(&((int##size##_t*)keys->dk_indices)[idx], (int##size##_t)value);
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#define ASSERT_OWNED_OR_SHARED(mp) \
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assert(_Py_IsOwnedByCurrentThread((PyObject *)mp) || IS_DICT_SHARED(mp));
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#define LOAD_KEYS_NENTRIES(d)
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#define LOCK_KEYS_IF_SPLIT(keys, kind) \
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if (kind == DICT_KEYS_SPLIT) { \
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LOCK_KEYS(dk); \
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LOCK_KEYS(keys); \
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}
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#define UNLOCK_KEYS_IF_SPLIT(keys, kind) \
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if (kind == DICT_KEYS_SPLIT) { \
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UNLOCK_KEYS(dk); \
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UNLOCK_KEYS(keys); \
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}
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static inline Py_ssize_t
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@ -212,7 +211,7 @@ set_values(PyDictObject *mp, PyDictValues *values)
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#define INCREF_KEYS(dk) _Py_atomic_add_ssize(&dk->dk_refcnt, 1)
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// Dec refs the keys object, giving the previous value
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#define DECREF_KEYS(dk) _Py_atomic_add_ssize(&dk->dk_refcnt, -1)
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#define LOAD_KEYS_NENTIRES(keys) _Py_atomic_load_ssize_relaxed(&keys->dk_nentries)
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#define LOAD_KEYS_NENTRIES(keys) _Py_atomic_load_ssize_relaxed(&keys->dk_nentries)
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#define INCREF_KEYS_FT(dk) dictkeys_incref(dk)
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#define DECREF_KEYS_FT(dk, shared) dictkeys_decref(_PyInterpreterState_GET(), dk, shared)
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@ -239,7 +238,7 @@ static inline void split_keys_entry_added(PyDictKeysObject *keys)
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#define STORE_SHARED_KEY(key, value) key = value
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#define INCREF_KEYS(dk) dk->dk_refcnt++
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#define DECREF_KEYS(dk) dk->dk_refcnt--
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#define LOAD_KEYS_NENTIRES(keys) keys->dk_nentries
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#define LOAD_KEYS_NENTRIES(keys) keys->dk_nentries
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#define INCREF_KEYS_FT(dk)
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#define DECREF_KEYS_FT(dk, shared)
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#define LOCK_KEYS_IF_SPLIT(keys, kind)
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@ -694,10 +693,15 @@ _PyDict_CheckConsistency(PyObject *op, int check_content)
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int splitted = _PyDict_HasSplitTable(mp);
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Py_ssize_t usable = USABLE_FRACTION(DK_SIZE(keys));
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// In the free-threaded build, shared keys may be concurrently modified,
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// so use atomic loads.
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Py_ssize_t dk_usable = FT_ATOMIC_LOAD_SSIZE_ACQUIRE(keys->dk_usable);
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Py_ssize_t dk_nentries = FT_ATOMIC_LOAD_SSIZE_ACQUIRE(keys->dk_nentries);
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CHECK(0 <= mp->ma_used && mp->ma_used <= usable);
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CHECK(0 <= keys->dk_usable && keys->dk_usable <= usable);
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CHECK(0 <= keys->dk_nentries && keys->dk_nentries <= usable);
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CHECK(keys->dk_usable + keys->dk_nentries <= usable);
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CHECK(0 <= dk_usable && dk_usable <= usable);
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CHECK(0 <= dk_nentries && dk_nentries <= usable);
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CHECK(dk_usable + dk_nentries <= usable);
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if (!splitted) {
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/* combined table */
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@ -714,6 +718,7 @@ _PyDict_CheckConsistency(PyObject *op, int check_content)
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}
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if (check_content) {
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LOCK_KEYS_IF_SPLIT(keys, keys->dk_kind);
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for (Py_ssize_t i=0; i < DK_SIZE(keys); i++) {
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Py_ssize_t ix = dictkeys_get_index(keys, i);
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CHECK(DKIX_DUMMY <= ix && ix <= usable);
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@ -769,6 +774,7 @@ _PyDict_CheckConsistency(PyObject *op, int check_content)
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CHECK(mp->ma_values->values[index] != NULL);
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}
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}
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UNLOCK_KEYS_IF_SPLIT(keys, keys->dk_kind);
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}
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return 1;
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@ -4037,7 +4043,7 @@ dict_equal_lock_held(PyDictObject *a, PyDictObject *b)
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/* can't be equal if # of entries differ */
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return 0;
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/* Same # of entries -- check all of 'em. Exit early on any diff. */
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for (i = 0; i < LOAD_KEYS_NENTIRES(a->ma_keys); i++) {
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for (i = 0; i < LOAD_KEYS_NENTRIES(a->ma_keys); i++) {
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PyObject *key, *aval;
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Py_hash_t hash;
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if (DK_IS_UNICODE(a->ma_keys)) {
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@ -27,16 +27,8 @@ race_top:_add_to_weak_set
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race_top:_in_weak_set
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race_top:_PyEval_EvalFrameDefault
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race_top:assign_version_tag
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race_top:insertdict
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race_top:lookup_tp_dict
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race_top:new_reference
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race_top:_PyDict_CheckConsistency
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race_top:_Py_dict_lookup_threadsafe
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race_top:_multiprocessing_SemLock_acquire_impl
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race_top:dictiter_new
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race_top:dictresize
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race_top:insert_to_emptydict
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race_top:insertdict
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race_top:list_get_item_ref
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race_top:make_pending_calls
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race_top:_Py_slot_tp_getattr_hook
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