https://github.com/python/cpython/commit/3c0525126ef95efe2f578e93db09f3282e3ca08f
commit: 3c0525126ef95efe2f578e93db09f3282e3ca08f
branch: main
author: Kumar Aditya <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2025-05-26T18:26:40Z
summary:
gh-134637: Fix performance regression in calling `ctypes` function pointer in
`free threading`. (#134702)
Fix performance regression in calling `ctypes` function pointer in `free
threading`.
files:
A Misc/NEWS.d/next/Library/2025-05-26-17-06-40.gh-issue-134637.9-3zRL.rst
M Modules/_ctypes/_ctypes.c
diff --git
a/Misc/NEWS.d/next/Library/2025-05-26-17-06-40.gh-issue-134637.9-3zRL.rst
b/Misc/NEWS.d/next/Library/2025-05-26-17-06-40.gh-issue-134637.9-3zRL.rst
new file mode 100644
index 00000000000000..2a4d8725210834
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-26-17-06-40.gh-issue-134637.9-3zRL.rst
@@ -0,0 +1 @@
+Fix performance regression in calling a :mod:`ctypes` function pointer in
:term:`free threading`.
diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index 7de6bb396b084e..7e8a133caa72ac 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -3610,6 +3610,45 @@ generic_pycdata_new(ctypes_state *st,
PyCFuncPtr_Type
*/
+static inline void
+atomic_xsetref(PyObject **field, PyObject *value)
+{
+#ifdef Py_GIL_DISABLED
+ PyObject *old = *field;
+ _Py_atomic_store_ptr(field, value);
+ Py_XDECREF(old);
+#else
+ Py_XSETREF(*field, value);
+#endif
+}
+/*
+ This function atomically loads the reference from *field, and
+ tries to get a new reference to it. If the incref fails,
+ it acquires critical section of obj and returns a new reference to the
*field.
+ In the general case, this avoids contention on acquiring the critical
section.
+*/
+static inline PyObject *
+atomic_xgetref(PyObject *obj, PyObject **field)
+{
+#ifdef Py_GIL_DISABLED
+ PyObject *value = _Py_atomic_load_ptr(field);
+ if (value == NULL) {
+ return NULL;
+ }
+ if (_Py_TryIncrefCompare(field, value)) {
+ return value;
+ }
+ Py_BEGIN_CRITICAL_SECTION(obj);
+ value = Py_XNewRef(*field);
+ Py_END_CRITICAL_SECTION();
+ return value;
+#else
+ return Py_XNewRef(*field);
+#endif
+}
+
+
+
/*[clinic input]
@critical_section
@setter
@@ -3626,7 +3665,7 @@ _ctypes_CFuncPtr_errcheck_set_impl(PyCFuncPtrObject
*self, PyObject *value)
return -1;
}
Py_XINCREF(value);
- Py_XSETREF(self->errcheck, value);
+ atomic_xsetref(&self->errcheck, value);
return 0;
}
@@ -3658,12 +3697,10 @@ static int
_ctypes_CFuncPtr_restype_set_impl(PyCFuncPtrObject *self, PyObject *value)
/*[clinic end generated code: output=0be0a086abbabf18 input=683c3bef4562ccc6]*/
{
- PyObject *checker, *oldchecker;
+ PyObject *checker;
if (value == NULL) {
- oldchecker = self->checker;
- self->checker = NULL;
- Py_CLEAR(self->restype);
- Py_XDECREF(oldchecker);
+ atomic_xsetref(&self->restype, NULL);
+ atomic_xsetref(&self->checker, NULL);
return 0;
}
ctypes_state *st = get_module_state_by_def(Py_TYPE(Py_TYPE(self)));
@@ -3679,11 +3716,9 @@ _ctypes_CFuncPtr_restype_set_impl(PyCFuncPtrObject
*self, PyObject *value)
if (PyObject_GetOptionalAttr(value, &_Py_ID(_check_retval_), &checker) <
0) {
return -1;
}
- oldchecker = self->checker;
- self->checker = checker;
Py_INCREF(value);
- Py_XSETREF(self->restype, value);
- Py_XDECREF(oldchecker);
+ atomic_xsetref(&self->checker, checker);
+ atomic_xsetref(&self->restype, value);
return 0;
}
@@ -3728,16 +3763,16 @@ _ctypes_CFuncPtr_argtypes_set_impl(PyCFuncPtrObject
*self, PyObject *value)
PyObject *converters;
if (value == NULL || value == Py_None) {
- Py_CLEAR(self->converters);
- Py_CLEAR(self->argtypes);
+ atomic_xsetref(&self->argtypes, NULL);
+ atomic_xsetref(&self->converters, NULL);
} else {
ctypes_state *st = get_module_state_by_def(Py_TYPE(Py_TYPE(self)));
converters = converters_from_argtypes(st, value);
if (!converters)
return -1;
- Py_XSETREF(self->converters, converters);
+ atomic_xsetref(&self->converters, converters);
Py_INCREF(value);
- Py_XSETREF(self->argtypes, value);
+ atomic_xsetref(&self->argtypes, value);
}
return 0;
}
@@ -4533,16 +4568,11 @@ _build_result(PyObject *result, PyObject *callargs,
}
static PyObject *
-PyCFuncPtr_call_lock_held(PyObject *op, PyObject *inargs, PyObject *kwds)
+PyCFuncPtr_call(PyObject *op, PyObject *inargs, PyObject *kwds)
{
- _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(op);
- PyObject *restype;
- PyObject *converters;
- PyObject *checker;
- PyObject *argtypes;
- PyObject *result;
- PyObject *callargs;
- PyObject *errcheck;
+ PyObject *result = NULL;
+ PyObject *callargs = NULL;
+ PyObject *ret = NULL;
#ifdef MS_WIN32
IUnknown *piunk = NULL;
#endif
@@ -4560,13 +4590,24 @@ PyCFuncPtr_call_lock_held(PyObject *op, PyObject
*inargs, PyObject *kwds)
}
assert(info); /* Cannot be NULL for PyCFuncPtrObject instances */
- restype = self->restype ? self->restype : info->restype;
- converters = self->converters ? self->converters : info->converters;
- checker = self->checker ? self->checker : info->checker;
- argtypes = self->argtypes ? self->argtypes : info->argtypes;
-/* later, we probably want to have an errcheck field in stginfo */
- errcheck = self->errcheck /* ? self->errcheck : info->errcheck */;
-
+ PyObject *restype = atomic_xgetref(op, &self->restype);
+ if (restype == NULL) {
+ restype = Py_XNewRef(info->restype);
+ }
+ PyObject *converters = atomic_xgetref(op, &self->converters);
+ if (converters == NULL) {
+ converters = Py_XNewRef(info->converters);
+ }
+ PyObject *checker = atomic_xgetref(op, &self->checker);
+ if (checker == NULL) {
+ checker = Py_XNewRef(info->checker);
+ }
+ PyObject *argtypes = atomic_xgetref(op, &self->argtypes);
+ if (argtypes == NULL) {
+ argtypes = Py_XNewRef(info->argtypes);
+ }
+ /* later, we probably want to have an errcheck field in stginfo */
+ PyObject *errcheck = atomic_xgetref(op, &self->errcheck);
pProc = *(void **)self->b_ptr;
#ifdef MS_WIN32
@@ -4577,25 +4618,25 @@ PyCFuncPtr_call_lock_held(PyObject *op, PyObject
*inargs, PyObject *kwds)
if (!this) {
PyErr_SetString(PyExc_ValueError,
"native com method call without 'this' parameter");
- return NULL;
+ goto finally;
}
if (!CDataObject_Check(st, this)) {
PyErr_SetString(PyExc_TypeError,
"Expected a COM this pointer as first argument");
- return NULL;
+ goto finally;
}
/* there should be more checks? No, in Python */
/* First arg is a pointer to an interface instance */
if (!this->b_ptr || *(void **)this->b_ptr == NULL) {
PyErr_SetString(PyExc_ValueError,
"NULL COM pointer access");
- return NULL;
+ goto finally;
}
piunk = *(IUnknown **)this->b_ptr;
if (NULL == piunk->lpVtbl) {
PyErr_SetString(PyExc_ValueError,
"COM method call without VTable");
- return NULL;
+ goto finally;
}
pProc = ((void **)piunk->lpVtbl)[self->index - 0x1000];
}
@@ -4603,8 +4644,9 @@ PyCFuncPtr_call_lock_held(PyObject *op, PyObject *inargs,
PyObject *kwds)
callargs = _build_callargs(st, self, argtypes,
inargs, kwds,
&outmask, &inoutmask, &numretvals);
- if (callargs == NULL)
- return NULL;
+ if (callargs == NULL) {
+ goto finally;
+ }
if (converters) {
int required = Py_SAFE_DOWNCAST(PyTuple_GET_SIZE(converters),
@@ -4623,7 +4665,7 @@ PyCFuncPtr_call_lock_held(PyObject *op, PyObject *inargs,
PyObject *kwds)
required,
required == 1 ? "" : "s",
actual);
- return NULL;
+ goto finally;
}
} else if (required != actual) {
Py_DECREF(callargs);
@@ -4632,7 +4674,7 @@ PyCFuncPtr_call_lock_held(PyObject *op, PyObject *inargs,
PyObject *kwds)
required,
required == 1 ? "" : "s",
actual);
- return NULL;
+ goto finally;
}
}
@@ -4663,23 +4705,19 @@ PyCFuncPtr_call_lock_held(PyObject *op, PyObject
*inargs, PyObject *kwds)
if (v == NULL || v != callargs) {
Py_DECREF(result);
Py_DECREF(callargs);
- return v;
+ ret = v;
+ goto finally;
}
Py_DECREF(v);
}
-
- return _build_result(result, callargs,
- outmask, inoutmask, numretvals);
-}
-
-static PyObject *
-PyCFuncPtr_call(PyObject *op, PyObject *inargs, PyObject *kwds)
-{
- PyObject *result;
- Py_BEGIN_CRITICAL_SECTION(op);
- result = PyCFuncPtr_call_lock_held(op, inargs, kwds);
- Py_END_CRITICAL_SECTION();
- return result;
+ ret = _build_result(result, callargs, outmask, inoutmask, numretvals);
+finally:
+ Py_XDECREF(restype);
+ Py_XDECREF(converters);
+ Py_XDECREF(checker);
+ Py_XDECREF(argtypes);
+ Py_XDECREF(errcheck);
+ return ret;
}
static int
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