https://github.com/python/cpython/commit/81c79961d2ee27dec90dbc0b72dfca7a5b2... commit: 81c79961d2ee27dec90dbc0b72dfca7a5b27de7a branch: main author: Dino Viehland <dinoviehland@meta.com> committer: DinoV <dinoviehland@gmail.com> date: 2024-02-28T14:53:19-08:00 summary: gh-112075: Use relaxed stores for places where we may race with when reading lock-free (#115786) files: M Objects/dictobject.c diff --git a/Objects/dictobject.c b/Objects/dictobject.c index 58fe973bc7a036..5016e255f70ef9 100644 --- a/Objects/dictobject.c +++ b/Objects/dictobject.c @@ -250,6 +250,14 @@ load_keys_nentries(PyDictObject *mp) #endif +#define STORE_KEY(ep, key) FT_ATOMIC_STORE_PTR_RELEASE(ep->me_key, key) +#define STORE_VALUE(ep, value) FT_ATOMIC_STORE_PTR_RELEASE(ep->me_value, value) +#define STORE_SPLIT_VALUE(mp, idx, value) FT_ATOMIC_STORE_PTR_RELEASE(mp->ma_values->values[idx], value) +#define STORE_HASH(ep, hash) FT_ATOMIC_STORE_SSIZE_RELAXED(ep->me_hash, hash) +#define STORE_KEYS_USABLE(keys, usable) FT_ATOMIC_STORE_SSIZE_RELAXED(keys->dk_usable, usable) +#define STORE_KEYS_NENTRIES(keys, nentries) FT_ATOMIC_STORE_SSIZE_RELAXED(keys->dk_nentries, nentries) +#define STORE_USED(mp, used) FT_ATOMIC_STORE_SSIZE_RELAXED(mp->ma_used, used) + #define PERTURB_SHIFT 5 /* @@ -1621,7 +1629,6 @@ insert_into_splitdictkeys(PyDictKeysObject *keys, PyObject *name) return ix; } - static inline int insert_combined_dict(PyInterpreterState *interp, PyDictObject *mp, Py_hash_t hash, PyObject *key, PyObject *value) @@ -1639,18 +1646,18 @@ insert_combined_dict(PyInterpreterState *interp, PyDictObject *mp, if (DK_IS_UNICODE(mp->ma_keys)) { PyDictUnicodeEntry *ep; ep = &DK_UNICODE_ENTRIES(mp->ma_keys)[mp->ma_keys->dk_nentries]; - ep->me_key = key; - ep->me_value = value; + STORE_KEY(ep, key); + STORE_VALUE(ep, value); } else { PyDictKeyEntry *ep; ep = &DK_ENTRIES(mp->ma_keys)[mp->ma_keys->dk_nentries]; - ep->me_key = key; - ep->me_hash = hash; - ep->me_value = value; + STORE_KEY(ep, key); + STORE_VALUE(ep, value); + STORE_HASH(ep, hash); } - mp->ma_keys->dk_usable--; - mp->ma_keys->dk_nentries++; + STORE_KEYS_USABLE(mp->ma_keys, mp->ma_keys->dk_usable - 1); + STORE_KEYS_NENTRIES(mp->ma_keys, mp->ma_keys->dk_nentries + 1); assert(mp->ma_keys->dk_usable >= 0); return 0; } @@ -1682,7 +1689,7 @@ insert_split_dict(PyInterpreterState *interp, PyDictObject *mp, Py_ssize_t index = keys->dk_nentries; _PyDictValues_AddToInsertionOrder(mp->ma_values, index); assert (mp->ma_values->values[index] == NULL); - mp->ma_values->values[index] = value; + STORE_SPLIT_VALUE(mp, index, value); split_keys_entry_added(keys); assert(keys->dk_usable >= 0); @@ -2013,8 +2020,8 @@ dictresize(PyInterpreterState *interp, PyDictObject *mp, } } - mp->ma_keys->dk_usable -= numentries; - mp->ma_keys->dk_nentries = numentries; + STORE_KEYS_USABLE(mp->ma_keys, mp->ma_keys->dk_usable - numentries); + STORE_KEYS_NENTRIES(mp->ma_keys, numentries); ASSERT_CONSISTENT(mp); return 0; } @@ -2507,15 +2514,15 @@ delitem_common(PyDictObject *mp, Py_hash_t hash, Py_ssize_t ix, if (DK_IS_UNICODE(mp->ma_keys)) { PyDictUnicodeEntry *ep = &DK_UNICODE_ENTRIES(mp->ma_keys)[ix]; old_key = ep->me_key; - ep->me_key = NULL; - ep->me_value = NULL; + STORE_KEY(ep, NULL); + STORE_VALUE(ep, NULL); } else { PyDictKeyEntry *ep = &DK_ENTRIES(mp->ma_keys)[ix]; old_key = ep->me_key; - ep->me_key = NULL; - ep->me_value = NULL; - ep->me_hash = 0; + STORE_KEY(ep, NULL); + STORE_VALUE(ep, NULL); + STORE_HASH(ep, 0); } Py_DECREF(old_key); } @@ -4393,8 +4400,8 @@ dict_popitem_impl(PyDictObject *self) PyTuple_SET_ITEM(res, 0, key); PyTuple_SET_ITEM(res, 1, value); /* We can't dk_usable++ since there is DKIX_DUMMY in indices */ - self->ma_keys->dk_nentries = i; - self->ma_used--; + STORE_KEYS_NENTRIES(self->ma_keys, i); + STORE_USED(self, self->ma_used - 1); self->ma_version_tag = new_version; ASSERT_CONSISTENT(self); return res;