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gh-112075: _Py_dict_lookup needs to lock shared keys (#117528) 

Lock shared keys in `Py_dict_lookup` and use thread-safe lookup in `insertdict`

Co-authored-by: Sam Gross <colesbury@gmail.com>
This commit is contained in:
Dino Viehland 2024-04-25 15:34:05 -07:00 committed by GitHub
parent c379de224c
commit d5df25268b
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GPG Key ID: B5690EEEBB952194
1 changed files with 159 additions and 128 deletions
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287
Objects/dictobject.c
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@ -162,6 +162,16 @@ ASSERT_DICT_LOCKED(PyObject *op)
assert(_Py_IsOwnedByCurrentThread((PyObject *)mp) || IS_DICT_SHARED(mp));
#define LOAD_KEYS_NENTRIES(d)
#define LOCK_KEYS_IF_SPLIT(keys, kind) \
if (kind == DICT_KEYS_SPLIT) { \
LOCK_KEYS(dk); \
}
#define UNLOCK_KEYS_IF_SPLIT(keys, kind) \
if (kind == DICT_KEYS_SPLIT) { \
UNLOCK_KEYS(dk); \
}
static inline Py_ssize_t
load_keys_nentries(PyDictObject *mp)
{
@ -195,6 +205,9 @@ set_values(PyDictObject *mp, PyDictValues *values)
#define DECREF_KEYS(dk) _Py_atomic_add_ssize(&dk->dk_refcnt, -1)
#define LOAD_KEYS_NENTIRES(keys) _Py_atomic_load_ssize_relaxed(&keys->dk_nentries)
#define INCREF_KEYS_FT(dk) dictkeys_incref(dk)
#define DECREF_KEYS_FT(dk, shared) dictkeys_decref(_PyInterpreterState_GET(), dk, shared)
static inline void split_keys_entry_added(PyDictKeysObject *keys)
{
ASSERT_KEYS_LOCKED(keys);
@ -216,6 +229,10 @@ static inline void split_keys_entry_added(PyDictKeysObject *keys)
#define INCREF_KEYS(dk) dk->dk_refcnt++
#define DECREF_KEYS(dk) dk->dk_refcnt--
#define LOAD_KEYS_NENTIRES(keys) keys->dk_nentries
#define INCREF_KEYS_FT(dk)
#define DECREF_KEYS_FT(dk, shared)
#define LOCK_KEYS_IF_SPLIT(keys, kind)
#define UNLOCK_KEYS_IF_SPLIT(keys, kind)
#define IS_DICT_SHARED(mp) (false)
#define SET_DICT_SHARED(mp)
#define LOAD_INDEX(keys, size, idx) ((const int##size##_t*)(keys->dk_indices))[idx]
@ -1171,6 +1188,14 @@ _PyDictKeys_StringLookup(PyDictKeysObject* dk, PyObject *key)
return unicodekeys_lookup_unicode(dk, key, hash);
}
#ifdef Py_GIL_DISABLED
static Py_ssize_t
unicodekeys_lookup_unicode_threadsafe(PyDictKeysObject* dk, PyObject *key,
Py_hash_t hash);
#endif
/*
The basic lookup function used by all operations.
This is based on Algorithm D from Knuth Vol. 3, Sec. 6.4.
@ -1200,10 +1225,33 @@ start:
if (kind != DICT_KEYS_GENERAL) {
if (PyUnicode_CheckExact(key)) {
#ifdef Py_GIL_DISABLED
if (kind == DICT_KEYS_SPLIT) {
// A split dictionaries keys can be mutated by other
// dictionaries but if we have a unicode key we can avoid
// locking the shared keys.
ix = unicodekeys_lookup_unicode_threadsafe(dk, key, hash);
if (ix == DKIX_KEY_CHANGED) {
LOCK_KEYS(dk);
ix = unicodekeys_lookup_unicode(dk, key, hash);
UNLOCK_KEYS(dk);
}
}
else {
ix = unicodekeys_lookup_unicode(dk, key, hash);
}
#else
ix = unicodekeys_lookup_unicode(dk, key, hash);
#endif
}
else {
INCREF_KEYS_FT(dk);
LOCK_KEYS_IF_SPLIT(dk, kind);
ix = unicodekeys_lookup_generic(mp, dk, key, hash);
UNLOCK_KEYS_IF_SPLIT(dk, kind);
DECREF_KEYS_FT(dk, IS_DICT_SHARED(mp));
if (ix == DKIX_KEY_CHANGED) {
goto start;
}
@ -1607,31 +1655,6 @@ insertion_resize(PyInterpreterState *interp, PyDictObject *mp, int unicode)
return dictresize(interp, mp, calculate_log2_keysize(GROWTH_RATE(mp)), unicode);
}
static Py_ssize_t
insert_into_splitdictkeys(PyDictKeysObject *keys, PyObject *name, Py_hash_t hash)
{
assert(PyUnicode_CheckExact(name));
ASSERT_KEYS_LOCKED(keys);
Py_ssize_t ix = unicodekeys_lookup_unicode(keys, name, hash);
if (ix == DKIX_EMPTY) {
if (keys->dk_usable <= 0) {
return DKIX_EMPTY;
}
/* Insert into new slot. */
keys->dk_version = 0;
Py_ssize_t hashpos = find_empty_slot(keys, hash);
ix = keys->dk_nentries;
PyDictUnicodeEntry *ep = &DK_UNICODE_ENTRIES(keys)[ix];
dictkeys_set_index(keys, hashpos, ix);
assert(ep->me_key == NULL);
ep->me_key = Py_NewRef(name);
split_keys_entry_added(keys);
}
assert (ix < SHARED_KEYS_MAX_SIZE);
return ix;
}
static inline int
insert_combined_dict(PyInterpreterState *interp, PyDictObject *mp,
Py_hash_t hash, PyObject *key, PyObject *value)
@ -1665,39 +1688,57 @@ insert_combined_dict(PyInterpreterState *interp, PyDictObject *mp,
return 0;
}
static int
insert_split_dict(PyInterpreterState *interp, PyDictObject *mp,
Py_hash_t hash, PyObject *key, PyObject *value)
static Py_ssize_t
insert_split_key(PyDictKeysObject *keys, PyObject *key, Py_hash_t hash)
{
PyDictKeysObject *keys = mp->ma_keys;
LOCK_KEYS(keys);
if (keys->dk_usable <= 0) {
/* Need to resize. */
UNLOCK_KEYS(keys);
int ins = insertion_resize(interp, mp, 1);
if (ins < 0) {
return -1;
}
assert(!_PyDict_HasSplitTable(mp));
return insert_combined_dict(interp, mp, hash, key, value);
assert(PyUnicode_CheckExact(key));
Py_ssize_t ix;
#ifdef Py_GIL_DISABLED
ix = unicodekeys_lookup_unicode_threadsafe(keys, key, hash);
if (ix >= 0) {
return ix;
}
#endif
Py_ssize_t hashpos = find_empty_slot(keys, hash);
dictkeys_set_index(keys, hashpos, keys->dk_nentries);
PyDictUnicodeEntry *ep;
ep = &DK_UNICODE_ENTRIES(keys)[keys->dk_nentries];
STORE_SHARED_KEY(ep->me_key, key);
Py_ssize_t index = keys->dk_nentries;
_PyDictValues_AddToInsertionOrder(mp->ma_values, index);
assert (mp->ma_values->values[index] == NULL);
STORE_SPLIT_VALUE(mp, index, value);
split_keys_entry_added(keys);
assert(keys->dk_usable >= 0);
LOCK_KEYS(keys);
ix = unicodekeys_lookup_unicode(keys, key, hash);
if (ix == DKIX_EMPTY && keys->dk_usable > 0) {
// Insert into new slot
keys->dk_version = 0;
Py_ssize_t hashpos = find_empty_slot(keys, hash);
ix = keys->dk_nentries;
dictkeys_set_index(keys, hashpos, ix);
PyDictUnicodeEntry *ep = &DK_UNICODE_ENTRIES(keys)[ix];
STORE_SHARED_KEY(ep->me_key, Py_NewRef(key));
split_keys_entry_added(keys);
}
assert (ix < SHARED_KEYS_MAX_SIZE);
UNLOCK_KEYS(keys);
return 0;
return ix;
}
static void
insert_split_value(PyInterpreterState *interp, PyDictObject *mp, PyObject *key, PyObject *value, Py_ssize_t ix)
{
assert(PyUnicode_CheckExact(key));
MAINTAIN_TRACKING(mp, key, value);
PyObject *old_value = mp->ma_values->values[ix];
if (old_value == NULL) {
uint64_t new_version = _PyDict_NotifyEvent(interp, PyDict_EVENT_ADDED, mp, key, value);
STORE_SPLIT_VALUE(mp, ix, Py_NewRef(value));
_PyDictValues_AddToInsertionOrder(mp->ma_values, ix);
mp->ma_used++;
mp->ma_version_tag = new_version;
}
else {
uint64_t new_version = _PyDict_NotifyEvent(interp, PyDict_EVENT_MODIFIED, mp, key, value);
STORE_SPLIT_VALUE(mp, ix, Py_NewRef(value));
mp->ma_version_tag = new_version;
Py_DECREF(old_value);
}
ASSERT_CONSISTENT(mp);
}
/*
@ -1720,6 +1761,21 @@ insertdict(PyInterpreterState *interp, PyDictObject *mp,
assert(mp->ma_keys->dk_kind == DICT_KEYS_GENERAL);
}
if (_PyDict_HasSplitTable(mp)) {
Py_ssize_t ix = insert_split_key(mp->ma_keys, key, hash);
if (ix != DKIX_EMPTY) {
insert_split_value(interp, mp, key, value, ix);
Py_DECREF(key);
Py_DECREF(value);
return 0;
}
/* No space in shared keys. Resize and continue below. */
if (insertion_resize(interp, mp, 1) < 0) {
goto Fail;
}
}
Py_ssize_t ix = _Py_dict_lookup(mp, key, hash, &old_value);
if (ix == DKIX_ERROR)
goto Fail;
@ -1727,24 +1783,17 @@ insertdict(PyInterpreterState *interp, PyDictObject *mp,
MAINTAIN_TRACKING(mp, key, value);
if (ix == DKIX_EMPTY) {
assert(!_PyDict_HasSplitTable(mp));
uint64_t new_version = _PyDict_NotifyEvent(
interp, PyDict_EVENT_ADDED, mp, key, value);
/* Insert into new slot. */
mp->ma_keys->dk_version = 0;
assert(old_value == NULL);
if (!_PyDict_HasSplitTable(mp)) {
if (insert_combined_dict(interp, mp, hash, key, value) < 0) {
goto Fail;
}
if (insert_combined_dict(interp, mp, hash, key, value) < 0) {
goto Fail;
}
else {
if (insert_split_dict(interp, mp, hash, key, value) < 0)
goto Fail;
}
mp->ma_used++;
mp->ma_version_tag = new_version;
mp->ma_used++;
ASSERT_CONSISTENT(mp);
return 0;
}
@ -1752,23 +1801,15 @@ insertdict(PyInterpreterState *interp, PyDictObject *mp,
if (old_value != value) {
uint64_t new_version = _PyDict_NotifyEvent(
interp, PyDict_EVENT_MODIFIED, mp, key, value);
if (_PyDict_HasSplitTable(mp)) {
STORE_SPLIT_VALUE(mp, ix, value);
if (old_value == NULL) {
_PyDictValues_AddToInsertionOrder(mp->ma_values, ix);
mp->ma_used++;
}
assert(old_value != NULL);
assert(!_PyDict_HasSplitTable(mp));
if (DK_IS_UNICODE(mp->ma_keys)) {
PyDictUnicodeEntry *ep = &DK_UNICODE_ENTRIES(mp->ma_keys)[ix];
STORE_VALUE(ep, value);
}
else {
assert(old_value != NULL);
if (DK_IS_UNICODE(mp->ma_keys)) {
PyDictUnicodeEntry *ep = &DK_UNICODE_ENTRIES(mp->ma_keys)[ix];
STORE_VALUE(ep, value);
}
else {
PyDictKeyEntry *ep = &DK_ENTRIES(mp->ma_keys)[ix];
STORE_VALUE(ep, value);
}
PyDictKeyEntry *ep = &DK_ENTRIES(mp->ma_keys)[ix];
STORE_VALUE(ep, value);
}
mp->ma_version_tag = new_version;
}
@ -4177,6 +4218,29 @@ dict_setdefault_ref_lock_held(PyObject *d, PyObject *key, PyObject *default_valu
}
}
if (_PyDict_HasSplitTable(mp)) {
Py_ssize_t ix = insert_split_key(mp->ma_keys, key, hash);
if (ix != DKIX_EMPTY) {
PyObject *value = mp->ma_values->values[ix];
int already_present = value != NULL;
if (!already_present) {
insert_split_value(interp, mp, key, default_value, ix);
value = default_value;
}
if (result) {
*result = incref_result ? Py_NewRef(value) : value;
}
return already_present;
}
/* No space in shared keys. Resize and continue below. */
if (insertion_resize(interp, mp, 1) < 0) {
goto error;
}
}
assert(!_PyDict_HasSplitTable(mp));
Py_ssize_t ix = _Py_dict_lookup(mp, key, hash, &value);
if (ix == DKIX_ERROR) {
if (result) {
@ -4186,29 +4250,17 @@ dict_setdefault_ref_lock_held(PyObject *d, PyObject *key, PyObject *default_valu
}
if (ix == DKIX_EMPTY) {
assert(!_PyDict_HasSplitTable(mp));
uint64_t new_version = _PyDict_NotifyEvent(
interp, PyDict_EVENT_ADDED, mp, key, default_value);
interp, PyDict_EVENT_ADDED, mp, key, default_value);
mp->ma_keys->dk_version = 0;
value = default_value;
if (!_PyDict_HasSplitTable(mp)) {
if (insert_combined_dict(interp, mp, hash, Py_NewRef(key), Py_NewRef(value)) < 0) {
Py_DECREF(key);
Py_DECREF(value);
if (result) {
*result = NULL;
}
return -1;
}
}
else {
if (insert_split_dict(interp, mp, hash, Py_NewRef(key), Py_NewRef(value)) < 0) {
Py_DECREF(key);
Py_DECREF(value);
if (result) {
*result = NULL;
}
return -1;
if (insert_combined_dict(interp, mp, hash, Py_NewRef(key), Py_NewRef(value)) < 0) {
Py_DECREF(key);
Py_DECREF(value);
if (result) {
*result = NULL;
}
}
@ -4222,29 +4274,19 @@ dict_setdefault_ref_lock_held(PyObject *d, PyObject *key, PyObject *default_valu
}
return 0;
}
else if (value == NULL) {
uint64_t new_version = _PyDict_NotifyEvent(
interp, PyDict_EVENT_ADDED, mp, key, default_value);
value = default_value;
assert(_PyDict_HasSplitTable(mp));
assert(mp->ma_values->values[ix] == NULL);
MAINTAIN_TRACKING(mp, key, value);
STORE_SPLIT_VALUE(mp, ix, Py_NewRef(value));
_PyDictValues_AddToInsertionOrder(mp->ma_values, ix);
mp->ma_used++;
mp->ma_version_tag = new_version;
ASSERT_CONSISTENT(mp);
if (result) {
*result = incref_result ? Py_NewRef(value) : value;
}
return 0;
}
assert(value != NULL);
ASSERT_CONSISTENT(mp);
if (result) {
*result = incref_result ? Py_NewRef(value) : value;
}
return 1;
error:
if (result) {
*result = NULL;
}
return -1;
}
int
@ -6699,18 +6741,7 @@ store_instance_attr_lock_held(PyObject *obj, PyDictValues *values,
assert(hash != -1);
}
#ifdef Py_GIL_DISABLED
// Try a thread-safe lookup to see if the index is already allocated
ix = unicodekeys_lookup_unicode_threadsafe(keys, name, hash);
if (ix == DKIX_EMPTY || ix == DKIX_KEY_CHANGED) {
// Lock keys and do insert
LOCK_KEYS(keys);
ix = insert_into_splitdictkeys(keys, name, hash);
UNLOCK_KEYS(keys);
}
#else
ix = insert_into_splitdictkeys(keys, name, hash);
#endif
ix = insert_split_key(keys, name, hash);
#ifdef Py_STATS
if (ix == DKIX_EMPTY) {