8000 gh-112075: Fix race in constructing dict for instance by DinoV · Pull Request #118499 · python/cpython · GitHub
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gh-112075: Fix race in constructing dict for instance #118499

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Merged
merged 4 commits into from
May 6, 2024
Merged

gh-112075: Fix race in constructing dict for instance #118499

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05092ed
Fix race in constructing dict for instance
DinoV Apr 30, 2024
2db4a3c
Fix PyObject_GenericGetDict, PyObject_GenericSetDict, and add test cases
DinoV May 2, 2024
f3f3445
Simplify incref's around new_dict_with_shared_keys, fix stats
DinoV May 6, 2024
9547a5f
remove stale comment and use requires_working_threading
DinoV May 6, 2024
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Simplify incref's around new_dict_with_shared_keys, fix stats 
Lock obj instead of using atomic, and fix reads/writes
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@DinoV
DinoV committed May 6, 2024
commit f3f3445bdbb67c71eba0bf5acdcfeb66296bee85
16 changes: 4 additions & 12 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -931,9 +931,9 @@ new_dict_with_shared_keys(PyInterpreterState *interp, PyDictKeysObject *keys)
size_t size = shared_keys_usable_size(keys);
PyDictValues *values = new_values(size);
if (values == NULL) {
dictkeys_decref(interp, keys, false);
return PyErr_NoMemory();
}
dictkeys_incref(keys);
for (size_t i = 0; i < size; i++) {
values->values[i] = NULL;
}
Expand Down Expand Up @@ -6693,8 +6693,6 @@ materialize_managed_dict_lock_held(PyObject *obj)
{
_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(obj);

OBJECT_STAT_INC(dict_materialized_on_request);

PyDictValues *values = _PyObject_InlineValues(obj);
PyInterpreterState *interp = _PyInterpreterState_GET();
PyDictKeysObject *keys = CACHED_KEYS(Py_TYPE(obj));
Expand Down Expand Up @@ -7205,8 +7203,6 @@ ensure_managed_dict(PyObject *obj)
goto done;
}
#endif
OBJECT_STAT_INC(dict_materialized_on_request);
dictkeys_incref(CACHED_KEYS(tp));
dict = (PyDictObject *)new_dict_with_shared_keys(_PyInterpreterState_GET(),
CACHED_KEYS(tp));
FT_ATOMIC_STORE_PTR_RELEASE(_PyObject_ManagedDictPointer(obj)->dict,
Expand All @@ -7226,7 +7222,7 @@ ensure_nonmanaged_dict(PyObject *obj, PyObject **dictptr)
{
PyDictKeysObject *cached;

PyObject *dict = FT_ATOMIC_LOAD_PTR_RELAXED(*dictptr);
PyObject *dict = FT_ATOMIC_LOAD_PTR_ACQUIRE(*dictptr);
if (dict == NULL) {
#ifdef Py_GIL_DISABLED
Py_BEGIN_CRITICAL_SECTION(obj);
Expand All @@ -7236,19 +7232,15 @@ ensure_nonmanaged_dict(PyObject *obj, PyObject **dictptr)
}
#endif
PyTypeObject *tp = Py_TYPE(obj);
if ((tp->tp_flags & Py_TPFLAGS_HEAPTYPE) && (cached = CACHED_KEYS(tp))) {
if (_PyType_HasFeature(tp, Py_TPFLAGS_HEAPTYPE) && (cached = CACHED_KEYS(tp))) {
PyInterpreterState *interp = _PyInterpreterState_GET();
assert(!_PyType_HasFeature(tp, Py_TPFLAGS_INLINE_VALUES));
dictkeys_incref(cached);
dict = new_dict_with_shared_keys(interp, cached);
if (dict == NULL) {
dictkeys_decref(interp, cached, false);
}
}
else {
dict = PyDict_New();
}
FT_ATOMIC_STORE_PTR_RELAXED(*dictptr, dict);
FT_ATOMIC_STORE_PTR_RELEASE(*dictptr, dict);
#ifdef Py_GIL_DISABLED
done:
Py_END_CRITICAL_SECTION();
Expand Down
6 changes: 2 additions & 4 deletions Objects/object.c
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Expand Up @@ -1789,11 +1789,9 @@ PyObject_GenericSetDict(PyObject *obj, PyObject *value, void *context)
"not a '%.200s'", Py_TYPE(value)->tp_name);
return -1;
}
#ifdef Py_GIL_DISABLED
Py_XDECREF(_Py_atomic_exchange_ptr(dictptr, Py_NewRef(value)));
#else
Py_BEGIN_CRITICAL_SECTION(obj);
Py_XSETREF(*dictptr, Py_NewRef(value));
#endif
Py_END_CRITICAL_SECTION();
return 0;
}

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