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[3.13] gh-117657: Fix data races reported by TSAN in some set methods (…
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…GH-120914) (#121240)

Refactor the fast Unicode hash check into `_PyObject_HashFast` and use relaxed
atomic loads in the free-threaded build.

After this change, the TSAN doesn't report data races for this method.
(cherry picked from commit 294e724)

Co-authored-by: AN Long <aisk@users.noreply.github.com>
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@miss-islington @aisk
miss-islington and aisk authored Jul 1, 2024
1 parent fc0b1cb commit 06fd745
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Showing 6 changed files with 81 additions and 121 deletions.
14 changes: 14 additions & 0 deletions Include/internal/pycore_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -628,6 +628,20 @@ _PyObject_IS_GC(PyObject *obj)
&& (type->tp_is_gc == NULL || type->tp_is_gc(obj)));
}

// Fast inlined version of PyObject_Hash()
static inline Py_hash_t
_PyObject_HashFast(PyObject *op)
{
if (PyUnicode_CheckExact(op)) {
Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(
_PyASCIIObject_CAST(op)->hash);
if (hash != -1) {
return hash;
}
}
return PyObject_Hash(op);
}

// Fast inlined version of PyType_IS_GC()
#define _PyType_IS_GC(t) _PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)

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9 changes: 3 additions & 6 deletions Modules/_collectionsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2537,12 +2537,9 @@ _collections__count_elements_impl(PyObject *module, PyObject *mapping,
if (key == NULL)
break;

if (!PyUnicode_CheckExact(key) ||
(hash = _PyASCIIObject_CAST(key)->hash) == -1)
{
hash = PyObject_Hash(key);
if (hash == -1)
goto done;
hash = _PyObject_HashFast(key);
if (hash == -1) {
goto done;
}

oldval = _PyDict_GetItem_KnownHash(mapping, key, hash);
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135 changes: 51 additions & 84 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -427,7 +427,7 @@ static inline Py_hash_t
unicode_get_hash(PyObject *o)
{
assert(PyUnicode_CheckExact(o));
return _PyASCIIObject_CAST(o)->hash;
return FT_ATOMIC_LOAD_SSIZE_RELAXED(_PyASCIIObject_CAST(o)->hash);
}

/* Print summary info about the state of the optimized allocator */
Expand Down Expand Up @@ -2170,13 +2170,10 @@ dict_getitem(PyObject *op, PyObject *key, const char *warnmsg)
}
PyDictObject *mp = (PyDictObject *)op;

Py_hash_t hash;
if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
PyErr_FormatUnraisable(warnmsg);
return NULL;
}
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
PyErr_FormatUnraisable(warnmsg);
return NULL;
}

PyThreadState *tstate = _PyThreadState_GET();
Expand Down Expand Up @@ -2225,12 +2222,9 @@ _PyDict_LookupIndex(PyDictObject *mp, PyObject *key)
assert(PyDict_CheckExact((PyObject*)mp));
assert(PyUnicode_CheckExact(key));

Py_hash_t hash = unicode_get_hash(key);
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
return -1;
}
return -1;
}

return _Py_dict_lookup(mp, key, hash, &value);
Expand Down Expand Up @@ -2301,14 +2295,10 @@ PyDict_GetItemRef(PyObject *op, PyObject *key, PyObject **result)
return -1;
}

Py_hash_t hash;
if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1)
{
hash = PyObject_Hash(key);
if (hash == -1) {
*result = NULL;
return -1;
}
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
*result = NULL;
return -1;
}

return _PyDict_GetItemRef_KnownHash((PyDictObject *)op, key, hash, result);
Expand All @@ -2320,13 +2310,10 @@ _PyDict_GetItemRef_Unicode_LockHeld(PyDictObject *op, PyObject *key, PyObject **
ASSERT_DICT_LOCKED(op);
assert(PyUnicode_CheckExact(key));

Py_hash_t hash;
if ((hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
*result = NULL;
return -1;
}
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
*result = NULL;
return -1;
}

PyObject *value;
Expand Down Expand Up @@ -2360,12 +2347,9 @@ PyDict_GetItemWithError(PyObject *op, PyObject *key)
PyErr_BadInternalCall();
return NULL;
}
if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1)
{
hash = PyObject_Hash(key);
if (hash == -1) {
return NULL;
}
hash = _PyObject_HashFast(key);
if (hash == -1) {
return NULL;
}

#ifdef Py_GIL_DISABLED
Expand Down Expand Up @@ -2433,10 +2417,9 @@ _PyDict_LoadGlobal(PyDictObject *globals, PyDictObject *builtins, PyObject *key)
Py_hash_t hash;
PyObject *value;

if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return NULL;
hash = _PyObject_HashFast(key);
if (hash == -1) {
return NULL;
}

/* namespace 1: globals */
Expand All @@ -2461,14 +2444,11 @@ setitem_take2_lock_held(PyDictObject *mp, PyObject *key, PyObject *value)
assert(key);
assert(value);
assert(PyDict_Check(mp));
Py_hash_t hash;
if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
Py_DECREF(key);
Py_DECREF(value);
return -1;
}
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
Py_DECREF(key);
Py_DECREF(value);
return -1;
}

PyInterpreterState *interp = _PyInterpreterState_GET();
Expand Down Expand Up @@ -2617,12 +2597,10 @@ delitem_common(PyDictObject *mp, Py_hash_t hash, Py_ssize_t ix,
int
PyDict_DelItem(PyObject *op, PyObject *key)
{
Py_hash_t hash;
assert(key);
if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return -1;
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
return -1;
}

return _PyDict_DelItem_KnownHash(op, key, hash);
Expand Down Expand Up @@ -2946,15 +2924,12 @@ pop_lock_held(PyObject *op, PyObject *key, PyObject **result)
return 0;
}

Py_hash_t hash;
if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
if (result) {
*result = NULL;
}
return -1;
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
if (result) {
*result = NULL;
}
return -1;
}
return _PyDict_Pop_KnownHash(dict, key, hash, result);
}
Expand Down Expand Up @@ -3285,10 +3260,9 @@ dict_subscript(PyObject *self, PyObject *key)
Py_hash_t hash;
PyObject *value;

if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return NULL;
hash = _PyObject_HashFast(key);
if (hash == -1) {
return NULL;
}
ix = _Py_dict_lookup_threadsafe(mp, key, hash, &value);
if (ix == DKIX_ERROR)
Expand Down Expand Up @@ -4172,10 +4146,9 @@ dict_get_impl(PyDictObject *self, PyObject *key, PyObject *default_value)
Py_hash_t hash;
Py_ssize_t ix;

if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return NULL;
hash = _PyObject_HashFast(key);
if (hash == -1) {
return NULL;
}
ix = _Py_dict_lookup_threadsafe(self, key, hash, &val);
if (ix == DKIX_ERROR)
Expand Down Expand Up @@ -4205,14 +4178,12 @@ dict_setdefault_ref_lock_held(PyObject *d, PyObject *key, PyObject *default_valu
return -1;
}

if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
if (result) {
*result = NULL;
}
return -1;
hash = _PyObject_HashFast(key);
if (hash == -1) {
if (result) {
*result = NULL;
}
return -1;
}

if (mp->ma_keys == Py_EMPTY_KEYS) {
Expand Down Expand Up @@ -4642,12 +4613,10 @@ static PyMethodDef mapp_methods[] = {
int
PyDict_Contains(PyObject *op, PyObject *key)
{
Py_hash_t hash;
Py_hash_t hash = _PyObject_HashFast(key);

if (!PyUnicode_CheckExact(key) || (hash = unicode_get_hash(key)) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return -1;
if (hash == -1) {
return -1;
}

return _PyDict_Contains_KnownHash(op, key, hash);
Expand Down Expand Up @@ -6727,11 +6696,9 @@ int
_PyDict_SetItem_LockHeld(PyDictObject *dict, PyObject *name, PyObject *value)
{
if (value == NULL) {
Py_hash_t hash;
if (!PyUnicode_CheckExact(name) || (hash = unicode_get_hash(name)) == -1) {
hash = PyObject_Hash(name);
if (hash == -1)
return -1;
Py_hash_t hash = _PyObject_HashFast(name);
if (hash == -1) {
return -1;
}
return delitem_knownhash_lock_held((PyObject *)dict, name, hash);
} else {
Expand Down
30 changes: 9 additions & 21 deletions Objects/setobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -365,41 +365,29 @@ set_discard_entry(PySetObject *so, PyObject *key, Py_hash_t hash)
static int
set_add_key(PySetObject *so, PyObject *key)
{
Py_hash_t hash;

if (!PyUnicode_CheckExact(key) ||
(hash = _PyASCIIObject_CAST(key)->hash) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return -1;
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
return -1;
}
return set_add_entry(so, key, hash);
}

static int
set_contains_key(PySetObject *so, PyObject *key)
{
Py_hash_t hash;

if (!PyUnicode_CheckExact(key) ||
(hash = _PyASCIIObject_CAST(key)->hash) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return -1;
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
return -1;
}
return set_contains_entry(so, key, hash);
}

static int
set_discard_key(PySetObject *so, PyObject *key)
{
Py_hash_t hash;

if (!PyUnicode_CheckExact(key) ||
(hash = _PyASCIIObject_CAST(key)->hash) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return -1;
Py_hash_t hash = _PyObject_HashFast(key);
if (hash == -1) {
return -1;
}
return set_discard_entry(so, key, hash);
}
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13 changes: 4 additions & 9 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5069,15 +5069,10 @@ find_name_in_mro(PyTypeObject *type, PyObject *name, int *error)
{
ASSERT_TYPE_LOCK_HELD();

Py_hash_t hash;
if (!PyUnicode_CheckExact(name) ||
(hash = _PyASCIIObject_CAST(name)->hash) == -1)
{
hash = PyObject_Hash(name);
if (hash == -1) {
*error = -1;
return NULL;
}
Py_hash_t hash = _PyObject_HashFast(name);
if (hash == -1) {
*error = -1;
return NULL;
}

/* Look in tp_dict of types in MRO */
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1 change: 0 additions & 1 deletion Tools/tsan/suppressions_free_threading.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,6 @@ race_top:assign_version_tag
race_top:insertdict
race_top:lookup_tp_dict
race_top:new_reference
race_top:set_contains_key
# https://gist.github.com/colesbury/d13d033f413b4ad07929d044bed86c35
race_top:set_discard_entry
race_top:_PyDict_CheckConsistency
Expand Down

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