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gh-130373: Avoid locking in _LOAD_ATTR_WITH_HINT #130372

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Merged
merged 2 commits into from
Mar 28, 2025
Merged

gh-130373: Avoid locking in _LOAD_ATTR_WITH_HINT #130372

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14eb91d
Avoid locking in _LOAD_ATTR_WITH_HINT
DinoV Feb 19, 2025
aeb389d
Deopt if not owned, and mark as shared in specializer
DinoV Mar 19, 2025
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4 changes: 4 additions & 0 deletions Include/internal/pycore_dict.h
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Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,10 @@ extern int _PyDict_Pop_KnownHash(
Py_hash_t hash,
PyObject **result);

#ifdef Py_GIL_DISABLED
PyAPI_FUNC(void) _PyDict_EnsureSharedOnRead(PyDictObject *mp);
#endif

#define DKIX_EMPTY (-1)
#define DKIX_DUMMY (-2) /* Used internally */
#define DKIX_ERROR (-3)
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6 changes: 6 additions & 0 deletions Objects/dictobject.c
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Expand Up @@ -1325,6 +1325,12 @@ ensure_shared_on_read(PyDictObject *mp)
Py_END_CRITICAL_SECTION();
}
}

void
_PyDict_EnsureSharedOnRead(PyDictObject *mp)
{
ensure_shared_on_read(mp);
}
#endif

static inline void
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28 changes: 15 additions & 13 deletions Python/bytecodes.c
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Expand Up @@ -2291,34 +2291,36 @@ dummy_func(
assert(Py_TYPE(owner_o)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
PyDictObject *dict = _PyObject_GetManagedDict(owner_o);
DEOPT_IF(dict == NULL);
PyDictKeysObject *dk = FT_ATOMIC_LOAD_PTR(dict->ma_keys);
assert(PyDict_CheckExact((PyObject *)dict));
#ifdef Py_GIL_DISABLED
DEOPT_IF(!_Py_IsOwnedByCurrentThread((PyObject *)dict) && !_PyObject_GC_IS_SHARED(dict));
#endif
PyObject *attr_o;
if (!LOCK_OBJECT(dict)) {
if (hint >= (size_t)FT_ATOMIC_LOAD_SSIZE_RELAXED(dk->dk_nentries)) {
DEOPT_IF(true);
}

if (hint >= (size_t)dict->ma_keys->dk_nentries) {
UNLOCK_OBJECT(dict);
DEOPT_IF(true);
}
PyObject *name = GETITEM(FRAME_CO_NAMES, oparg>>1);
if (dict->ma_keys->dk_kind != DICT_KEYS_UNICODE) {
UNLOCK_OBJECT(dict);
if (dk->dk_kind != DICT_KEYS_UNICODE) {
DEOPT_IF(true);
}
PyDictUnicodeEntry *ep = DK_UNICODE_ENTRIES(dict->ma_keys) + hint;
if (ep->me_key != name) {
UNLOCK_OBJECT(dict);
PyDictUnicodeEntry *ep = DK_UNICODE_ENTRIES(dk) + hint;
if (FT_ATOMIC_LOAD_PTR_RELAXED(ep->me_key) != name) {
DEOPT_IF(true);
}
attr_o = ep->me_value;
attr_o = FT_ATOMIC_LOAD_PTR(ep->me_value);
if (attr_o == NULL) {
UNLOCK_OBJECT(dict);
DEOPT_IF(true);
}
STAT_INC(LOAD_ATTR, hit);
#ifdef Py_GIL_DISABLED
if (!_Py_TryIncrefCompareStackRef(&ep->me_value, attr_o, &attr)) {
DEOPT_IF(true);
}
#else
attr = PyStackRef_FromPyObjectNew(attr_o);
UNLOCK_OBJECT(dict);
#endif
PyStackRef_CLOSE(owner);
}

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33 changes: 19 additions & 14 deletions Python/executor_cases.c.h
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34 changes: 20 additions & 14 deletions Python/generated_cases.c.h
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3 changes: 3 additions & 0 deletions Python/specialize.c
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Expand Up @@ -1009,6 +1009,9 @@ specialize_dict_access_hint(
_PyAttrCache *cache = (_PyAttrCache *)(instr + 1);

_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(dict);
#ifdef Py_GIL_DISABLED
_PyDict_EnsureSharedOnRead(dict);
#endif

// We found an instance with a __dict__.
if (_PyDict_HasSplitTable(dict)) {
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