https://github.com/python/cpython/commit/4c12a2db15639fe1b28f1f0f807a18fb7b71d851
commit: 4c12a2db15639fe1b28f1f0f807a18fb7b71d851
branch: main
author: Tomasz Pytel <tompy...@gmail.com>
committer: vstinner <vstin...@python.org>
date: 2025-04-14T18:31:19+02:00
summary:
gh-131757: allow lru_cache functions to execute concurrently (#131758)
files:
A Misc/NEWS.d/next/Library/2025-03-26-10-56-22.gh-issue-131757.pFRdmN.rst
M Include/internal/pycore_pyatomic_ft_wrappers.h
M Modules/_functoolsmodule.c
diff --git a/Include/internal/pycore_pyatomic_ft_wrappers.h
b/Include/internal/pycore_pyatomic_ft_wrappers.h
index d755d03a5fa190..3e41e2fd1569ca 100644
--- a/Include/internal/pycore_pyatomic_ft_wrappers.h
+++ b/Include/internal/pycore_pyatomic_ft_wrappers.h
@@ -109,6 +109,8 @@ extern "C" {
_Py_atomic_store_ullong_relaxed(&value, new_value)
#define FT_ATOMIC_LOAD_ULLONG_RELAXED(value) \
_Py_atomic_load_ullong_relaxed(&value)
+#define FT_ATOMIC_ADD_SSIZE(value, new_value) \
+ (void)_Py_atomic_add_ssize(&value, new_value)
#else
#define FT_ATOMIC_LOAD_PTR(value) value
@@ -156,6 +158,7 @@ extern "C" {
#define FT_ATOMIC_STORE_LLONG_RELAXED(value, new_value) value = new_value
#define FT_ATOMIC_LOAD_ULLONG_RELAXED(value) value
#define FT_ATOMIC_STORE_ULLONG_RELAXED(value, new_value) value = new_value
+#define FT_ATOMIC_ADD_SSIZE(value, new_value) (void)(value += new_value)
#endif
diff --git
a/Misc/NEWS.d/next/Library/2025-03-26-10-56-22.gh-issue-131757.pFRdmN.rst
b/Misc/NEWS.d/next/Library/2025-03-26-10-56-22.gh-issue-131757.pFRdmN.rst
new file mode 100644
index 00000000000000..89f71ca113aa3d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-03-26-10-56-22.gh-issue-131757.pFRdmN.rst
@@ -0,0 +1 @@
+Make :func:`functools.lru_cache` call the cached function unlocked to allow
concurrency.
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index c84779268eb12e..e6c454faf4b16f 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -4,6 +4,7 @@
#include "pycore_long.h" // _PyLong_GetZero()
#include "pycore_moduleobject.h" // _PyModule_GetState()
#include "pycore_object.h" // _PyObject_GC_TRACK
+#include "pycore_pyatomic_ft_wrappers.h"
#include "pycore_pystate.h" // _PyThreadState_GET()
#include "pycore_tuple.h" // _PyTuple_ITEMS()
@@ -40,7 +41,6 @@ get_functools_state(PyObject *module)
return (_functools_state *)state;
}
-
/* partial object **********************************************************/
@@ -1016,7 +1016,7 @@ _functools_reduce_impl(PyObject *module, PyObject *func,
PyObject *seq,
if (result == NULL)
PyErr_SetString(PyExc_TypeError,
- "reduce() of empty iterable with no initial value");
+ "reduce() of empty iterable with no initial value");
Py_DECREF(it);
return result;
@@ -1173,7 +1173,7 @@ uncached_lru_cache_wrapper(lru_cache_object *self,
PyObject *args, PyObject *kwd
{
PyObject *result;
- self->misses++;
+ FT_ATOMIC_ADD_SSIZE(self->misses, 1);
result = PyObject_Call(self->func, args, kwds);
if (!result)
return NULL;
@@ -1193,18 +1193,17 @@ infinite_lru_cache_wrapper(lru_cache_object *self,
PyObject *args, PyObject *kwd
Py_DECREF(key);
return NULL;
}
- result = _PyDict_GetItem_KnownHash(self->cache, key, hash);
- if (result) {
- Py_INCREF(result);
- self->hits++;
+ int res = _PyDict_GetItemRef_KnownHash((PyDictObject *)self->cache, key,
hash, &result);
+ if (res > 0) {
+ FT_ATOMIC_ADD_SSIZE(self->hits, 1);
Py_DECREF(key);
return result;
}
- if (PyErr_Occurred()) {
+ if (res < 0) {
Py_DECREF(key);
return NULL;
}
- self->misses++;
+ FT_ATOMIC_ADD_SSIZE(self->misses, 1);
result = PyObject_Call(self->func, args, kwds);
if (!result) {
Py_DECREF(key);
@@ -1279,50 +1278,65 @@ lru_cache_prepend_link(lru_cache_object *self,
lru_list_elem *link)
so that we know the cache is a consistent state.
*/
-static PyObject *
-bounded_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject
*kwds)
+static int
+bounded_lru_cache_get_lock_held(lru_cache_object *self, PyObject *args,
PyObject *kwds,
+ PyObject **result, PyObject **key, Py_hash_t
*hash)
{
+ _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
lru_list_elem *link;
- PyObject *key, *result, *testresult;
- Py_hash_t hash;
- key = lru_cache_make_key(self->kwd_mark, args, kwds, self->typed);
- if (!key)
- return NULL;
- hash = PyObject_Hash(key);
- if (hash == -1) {
- Py_DECREF(key);
- return NULL;
+ PyObject *key_ = *key = lru_cache_make_key(self->kwd_mark, args, kwds,
self->typed);
+ if (!key_)
+ return -1;
+ Py_hash_t hash_ = *hash = PyObject_Hash(key_);
+ if (hash_ == -1) {
+ Py_DECREF(key_); /* dead reference left in *key, is not used */
+ return -1;
}
- link = (lru_list_elem *)_PyDict_GetItem_KnownHash(self->cache, key, hash);
- if (link != NULL) {
+ int res = _PyDict_GetItemRef_KnownHash_LockHeld((PyDictObject
*)self->cache, key_, hash_,
+ (PyObject **)&link);
+ if (res > 0) {
lru_cache_extract_link(link);
lru_cache_append_link(self, link);
- result = link->result;
- self->hits++;
- Py_INCREF(result);
- Py_DECREF(key);
- return result;
+ *result = link->result;
+ FT_ATOMIC_ADD_SSIZE(self->hits, 1);
+ Py_INCREF(link->result);
+ Py_DECREF(link);
+ Py_DECREF(key_);
+ return 1;
}
- if (PyErr_Occurred()) {
- Py_DECREF(key);
- return NULL;
+ if (res < 0) {
+ Py_DECREF(key_);
+ return -1;
}
- self->misses++;
- result = PyObject_Call(self->func, args, kwds);
+ FT_ATOMIC_ADD_SSIZE(self->misses, 1);
+ return 0;
+}
+
+static PyObject *
+bounded_lru_cache_update_lock_held(lru_cache_object *self,
+ PyObject *result, PyObject *key, Py_hash_t
hash)
+{
+ _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
+ lru_list_elem *link;
+ PyObject *testresult;
+ int res;
+
if (!result) {
Py_DECREF(key);
return NULL;
}
- testresult = _PyDict_GetItem_KnownHash(self->cache, key, hash);
- if (testresult != NULL) {
+ res = _PyDict_GetItemRef_KnownHash_LockHeld((PyDictObject *)self->cache,
key, hash,
+ &testresult);
+ if (res > 0) {
/* Getting here means that this same key was added to the cache
during the PyObject_Call(). Since the link update is already
done, we need only return the computed result. */
+ Py_DECREF(testresult);
Py_DECREF(key);
return result;
}
- if (PyErr_Occurred()) {
+ if (res < 0) {
/* This is an unusual case since this same lookup
did not previously trigger an error during lookup.
Treat it the same as an error in user function
@@ -1386,8 +1400,8 @@ bounded_lru_cache_wrapper(lru_cache_object *self,
PyObject *args, PyObject *kwds
The cache dict holds one reference to the link.
We created one other reference when the link was created.
The linked list only has borrowed references. */
- int res = _PyDict_Pop_KnownHash((PyDictObject*)self->cache, link->key,
- link->hash, &popresult);
+ res = _PyDict_Pop_KnownHash((PyDictObject*)self->cache, link->key,
+ link->hash, &popresult);
if (res < 0) {
/* An error arose while trying to remove the oldest key (the one
being evicted) from the cache. We restore the link to its
@@ -1445,6 +1459,37 @@ bounded_lru_cache_wrapper(lru_cache_object *self,
PyObject *args, PyObject *kwds
return result;
}
+static PyObject *
+bounded_lru_cache_wrapper(lru_cache_object *self, PyObject *args, PyObject
*kwds)
+{
+ PyObject *key, *result;
+ Py_hash_t hash;
+ int res;
+
+ Py_BEGIN_CRITICAL_SECTION(self);
+ res = bounded_lru_cache_get_lock_held(self, args, kwds, &result, &key,
&hash);
+ Py_END_CRITICAL_SECTION();
+
+ if (res < 0) {
+ return NULL;
+ }
+ if (res > 0) {
+ return result;
+ }
+
+ result = PyObject_Call(self->func, args, kwds);
+
+ Py_BEGIN_CRITICAL_SECTION(self);
+ /* Note: key will be stolen in the below function, and
+ result may be stolen or sometimes re-returned as a passthrough.
+ Treat both as being stolen.
+ */
+ result = bounded_lru_cache_update_lock_held(self, result, key, hash);
+ Py_END_CRITICAL_SECTION();
+
+ return result;
+}
+
static PyObject *
lru_cache_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
@@ -1577,9 +1622,7 @@ lru_cache_call(PyObject *op, PyObject *args, PyObject
*kwds)
{
lru_cache_object *self = lru_cache_object_CAST(op);
PyObject *result;
- Py_BEGIN_CRITICAL_SECTION(self);
result = self->wrapper(self, args, kwds);
- Py_END_CRITICAL_SECTION();
return result;
}
@@ -1606,11 +1649,15 @@ _functools__lru_cache_wrapper_cache_info_impl(PyObject
*self)
lru_cache_object *_self = (lru_cache_object *) self;
if (_self->maxsize == -1) {
return PyObject_CallFunction(_self->cache_info_type, "nnOn",
- _self->hits, _self->misses, Py_None,
+ FT_ATOMIC_LOAD_SSIZE_RELAXED(_self->hits),
+
FT_ATOMIC_LOAD_SSIZE_RELAXED(_self->misses),
+ Py_None,
PyDict_GET_SIZE(_self->cache));
}
return PyObject_CallFunction(_self->cache_info_type, "nnnn",
- _self->hits, _self->misses, _self->maxsize,
+ FT_ATOMIC_LOAD_SSIZE_RELAXED(_self->hits),
+ FT_ATOMIC_LOAD_SSIZE_RELAXED(_self->misses),
+ _self->maxsize,
PyDict_GET_SIZE(_self->cache));
}
@@ -1627,7 +1674,8 @@ _functools__lru_cache_wrapper_cache_clear_impl(PyObject
*self)
{
lru_cache_object *_self = (lru_cache_object *) self;
lru_list_elem *list = lru_cache_unlink_list(_self);
- _self->hits = _self->misses = 0;
+ FT_ATOMIC_STORE_SSIZE_RELAXED(_self->hits, 0);
+ FT_ATOMIC_STORE_SSIZE_RELAXED(_self->misses, 0);
PyDict_Clear(_self->cache);
lru_cache_clear_list(list);
Py_RETURN_NONE;
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