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gh-104252: Immortalize Py_EMPTY_KEYS (gh-104253) 

This was missed in gh-19474.  It matters for with a per-interpreter GIL since PyDictKeysObject.dk_refcnt breaks isolation and leads to races.
This commit is contained in:
Eric Snow 2023-05-10 07:28:40 -06:00 committed by GitHub
parent 2dcb289ed0
commit b8f7ab5783
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 27 additions and 14 deletions
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5
Include/internal/pycore_dict_state.h
View File

@ -38,6 +38,11 @@ struct _Py_dict_state {
PyDict_WatchCallback watchers[DICT_MAX_WATCHERS];
};
#define _dict_state_INIT \
{ \
.next_keys_version = 2, \
}
#ifdef __cplusplus
}

4
Include/internal/pycore_runtime_init.h
View File

@ -107,9 +107,7 @@ extern PyTypeObject _PyExc_MemoryError;
}, \
}, \
.dtoa = _dtoa_state_INIT(&(INTERP)), \
.dict_state = { \
.next_keys_version = 2, \
}, \
.dict_state = _dict_state_INIT, \
.func_state = { \
.next_version = 1, \
}, \

32
Objects/dictobject.c
View File

@ -300,9 +300,19 @@ _PyDict_DebugMallocStats(FILE *out)
static void free_keys_object(PyInterpreterState *interp, PyDictKeysObject *keys);
/* PyDictKeysObject has refcounts like PyObject does, so we have the
following two functions to mirror what Py_INCREF() and Py_DECREF() do.
(Keep in mind that PyDictKeysObject isn't actually a PyObject.)
Likewise a PyDictKeysObject can be immortal (e.g. Py_EMPTY_KEYS),
so we apply a naive version of what Py_INCREF() and Py_DECREF() do
for immortal objects. */
static inline void
dictkeys_incref(PyDictKeysObject *dk)
{
if (dk->dk_refcnt == _Py_IMMORTAL_REFCNT) {
return;
}
#ifdef Py_REF_DEBUG
_Py_IncRefTotal(_PyInterpreterState_GET());
#endif
@ -312,6 +322,9 @@ dictkeys_incref(PyDictKeysObject *dk)
static inline void
dictkeys_decref(PyInterpreterState *interp, PyDictKeysObject *dk)
{
if (dk->dk_refcnt == _Py_IMMORTAL_REFCNT) {
return;
}
assert(dk->dk_refcnt > 0);
#ifdef Py_REF_DEBUG
_Py_DecRefTotal(_PyInterpreterState_GET());
@ -447,7 +460,7 @@ estimate_log2_keysize(Py_ssize_t n)
* (which cannot fail and thus can do no allocation).
*/
static PyDictKeysObject empty_keys_struct = {
1, /* dk_refcnt */
_Py_IMMORTAL_REFCNT, /* dk_refcnt */
0, /* dk_log2_size */
0, /* dk_log2_index_bytes */
DICT_KEYS_UNICODE, /* dk_kind */
@ -779,6 +792,7 @@ clone_combined_dict_keys(PyDictObject *orig)
assert(PyDict_Check(orig));
assert(Py_TYPE(orig)->tp_iter == (getiterfunc)dict_iter);
assert(orig->ma_values == NULL);
assert(orig->ma_keys != Py_EMPTY_KEYS);
assert(orig->ma_keys->dk_refcnt == 1);
size_t keys_size = _PyDict_KeysSize(orig->ma_keys);
@ -833,7 +847,7 @@ PyObject *
PyDict_New(void)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
dictkeys_incref(Py_EMPTY_KEYS);
/* We don't incref Py_EMPTY_KEYS here because it is immortal. */
return new_dict(interp, Py_EMPTY_KEYS, NULL, 0, 0);
}
@ -1331,7 +1345,7 @@ insert_to_emptydict(PyInterpreterState *interp, PyDictObject *mp,
Py_DECREF(value);
return -1;
}
dictkeys_decref(interp, Py_EMPTY_KEYS);
/* We don't decref Py_EMPTY_KEYS here because it is immortal. */
mp->ma_keys = newkeys;
mp->ma_values = NULL;
@ -1529,14 +1543,10 @@ dictresize(PyInterpreterState *interp, PyDictObject *mp,
// We can not use free_keys_object here because key's reference
// are moved already.
if (oldkeys != Py_EMPTY_KEYS) {
#ifdef Py_REF_DEBUG
_Py_DecRefTotal(_PyInterpreterState_GET());
_Py_DecRefTotal(_PyInterpreterState_GET());
#endif
if (oldkeys == Py_EMPTY_KEYS) {
oldkeys->dk_refcnt--;
assert(oldkeys->dk_refcnt > 0);
}
else {
assert(oldkeys->dk_kind != DICT_KEYS_SPLIT);
assert(oldkeys->dk_refcnt == 1);
#if PyDict_MAXFREELIST > 0
@ -2080,8 +2090,8 @@ PyDict_Clear(PyObject *op)
dictkeys_decref(interp, oldkeys);
}
else {
assert(oldkeys->dk_refcnt == 1);
dictkeys_decref(interp, oldkeys);
assert(oldkeys->dk_refcnt == 1);
dictkeys_decref(interp, oldkeys);
}
ASSERT_CONSISTENT(mp);
}