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Issue #28969: Fixed race condition in C implementation of functools.lru_cache.

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KeyError could be raised when cached function with full cache was
simultaneously called from differen threads with the same uncached arguments.
This commit is contained in:
Serhiy Storchaka 2017-01-12 19:12:21 +02:00
commit 42e1ea9a10
5 changed files with 78 additions and 29 deletions
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31
Objects/dictobject.c
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@ -1829,9 +1829,8 @@ PyDict_Next(PyObject *op, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue)
/* Internal version of dict.pop(). */
PyObject *
_PyDict_Pop(PyObject *dict, PyObject *key, PyObject *deflt)
_PyDict_Pop_KnownHash(PyObject *dict, PyObject *key, Py_hash_t hash, PyObject *deflt)
{
Py_hash_t hash;
Py_ssize_t ix, hashpos;
PyObject *old_value, *old_key;
PyDictKeyEntry *ep;
@ -1849,12 +1848,6 @@ _PyDict_Pop(PyObject *dict, PyObject *key, PyObject *deflt)
_PyErr_SetKeyError(key);
return NULL;
}
if (!PyUnicode_CheckExact(key) ||
(hash = ((PyASCIIObject *) key)->hash) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return NULL;
}
ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &value_addr, &hashpos);
if (ix == DKIX_ERROR)
return NULL;
@ -1892,6 +1885,28 @@ _PyDict_Pop(PyObject *dict, PyObject *key, PyObject *deflt)
return old_value;
}
PyObject *
_PyDict_Pop(PyObject *dict, PyObject *key, PyObject *deflt)
{
Py_hash_t hash;
if (((PyDictObject *)dict)->ma_used == 0) {
if (deflt) {
Py_INCREF(deflt);
return deflt;
}
_PyErr_SetKeyError(key);
return NULL;
}
if (!PyUnicode_CheckExact(key) ||
(hash = ((PyASCIIObject *) key)->hash) == -1) {
hash = PyObject_Hash(key);
if (hash == -1)
return NULL;
}
return _PyDict_Pop_KnownHash(dict, key, hash, deflt);
}
/* Internal version of dict.from_keys(). It is subclass-friendly. */
PyObject *
_PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)