python · sobolevn · Jul 8, 2026 · Jul 8, 2026 · Jul 8, 2026
diff --git a/...t_free_threading/test_func_annotations.py → ...test/test_free_threading/test_function.py b/...t_free_threading/test_func_annotations.py → ...test/test_free_threading/test_function.py
@@ -2,9 +2,8 @@
 import unittest
 import inspect
 from threading import Barrier
-from unittest import TestCase
 
-from test.support import threading_helper, Py_GIL_DISABLED
+from test.support import threading_helper
 
 threading_helper.requires_working_threading(module=True)
 
@@ -25,11 +24,48 @@ def set_func_annotation(f, b):
     return f.__annotations__
 
 
-@unittest.skipUnless(Py_GIL_DISABLED, "Enable only in FT build")
-class TestFTFuncAnnotations(TestCase):
+class TestFunction(unittest.TestCase):
     NUM_THREADS = 4
 
-    def test_concurrent_read(self):
+    def test_name_attribute_race(self):
+        # gh-153297
+        def shared_func():
+            return 1
+
+        def setter():
+            for i in range(2000):
+                shared_func.__name__ = "q_%d_%d" % (id(i), i & 15)
+
+        def reader():
+            for _ in range(2000):
+                _ = shared_func.__name__
+                repr(shared_func)
+
+        threading_helper.run_concurrently([
+            *[setter for _ in range(6)],
+            *[reader for _ in range(4)],
+        ])
+
+    def test_qualname_attribute_race(self):
+        # gh-153297
+        def shared_func():
+            return 1
+
+        def setter():
+            for i in range(2000):
+                shared_func.__qualname__ = "q_%d_%d" % (id(i), i & 15)
+
+        def reader():
+            for _ in range(2000):
+                _ = shared_func.__qualname__
+                repr(shared_func)
+
+        threading_helper.run_concurrently([
+            *[setter for _ in range(6)],
+            *[reader for _ in range(4)],
+        ])
+
+    def test_concurrent_read_annotations(self):
         def f(x: int) -> int:
             return x + 1
 
@@ -50,7 +86,7 @@ def f(x: int) -> int:
                     self.assertIsNotNone(annotate)
                     self.assertEqual(annotate, {'x': int, 'return': int})
 
-    def test_concurrent_write(self):
+    def test_concurrent_write_annotations(self):
         def bar(x: int, y: float) -> float:
             return y ** x
 

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-08-15-09-41.gh-issue-153297.hWVsUZ.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-08-15-09-41.gh-issue-153297.hWVsUZ.rst
@@ -0,0 +1,2 @@
+Fix data race on assigning ``__name__`` and ``__qualname__`` attrs to
+function objects on FT builds.
diff --git a/Objects/clinic/funcobject.c.h b/Objects/clinic/funcobject.c.h
diff --git a/Objects/funcobject.c b/Objects/funcobject.c
@@ -690,48 +690,72 @@ func_set_code(PyObject *self, PyObject *value, void *Py_UNUSED(ignored))
     return 0;
 }
 
+/*[clinic input]
+@critical_section
+@getter
+function.__name__
+[clinic start generated code]*/
+
 static PyObject *
-func_get_name(PyObject *self, void *Py_UNUSED(ignored))
+function___name___get_impl(PyFunctionObject *self)
+/*[clinic end generated code: output=436852c5b4f6d259 input=3f1d1304d3fd103b]*/
 {
-    PyFunctionObject *op = _PyFunction_CAST(self);
-    return Py_NewRef(op->func_name);
+    return Py_NewRef(self->func_name);
 }
 
+/*[clinic input]
+@critical_section
+@setter
+function.__name__
+[clinic start generated code]*/
+
 static int
-func_set_name(PyObject *self, PyObject *value, void *Py_UNUSED(ignored))
+function___name___set_impl(PyFunctionObject *self, PyObject *value)
+/*[clinic end generated code: output=2c571635b003b9cc input=705634aafaa00198]*/
 {
-    PyFunctionObject *op = _PyFunction_CAST(self);
     /* Not legal to del f.func_name or to set it to anything
      * other than a string object. */
     if (value == NULL || !PyUnicode_Check(value)) {
         PyErr_SetString(PyExc_TypeError,
                         "__name__ must be set to a string object");
         return -1;
     }
-    Py_XSETREF(op->func_name, Py_NewRef(value));
+    Py_XSETREF(self->func_name, Py_NewRef(value));
     return 0;
 }
 
+/*[clinic input]
+@critical_section
+@getter
+function.__qualname__
+[clinic start generated code]*/
+
 static PyObject *
-func_get_qualname(PyObject *self, void *Py_UNUSED(ignored))
+function___qualname___get_impl(PyFunctionObject *self)
+/*[clinic end generated code: output=8fbd60e64464da5f input=761d5ab45fc13493]*/
 {
-    PyFunctionObject *op = _PyFunction_CAST(self);
-    return Py_NewRef(op->func_qualname);
+    return Py_NewRef(self->func_qualname);
 }
 
+/*[clinic input]
+@critical_section
+@setter
+function.__qualname__
+[clinic start generated code]*/
+
 static int
-func_set_qualname(PyObject *self, PyObject *value, void *Py_UNUSED(ignored))
+function___qualname___set_impl(PyFunctionObject *self, PyObject *value)
+/*[clinic end generated code: output=4cc5e270fd55f139 input=c803ac4dfdf04c87]*/
 {
-    PyFunctionObject *op = _PyFunction_CAST(self);
     /* Not legal to del f.__qualname__ or to set it to anything
      * other than a string object. */
     if (value == NULL || !PyUnicode_Check(value)) {
         PyErr_SetString(PyExc_TypeError,
                         "__qualname__ must be set to a string object");
         return -1;
     }
-    handle_func_event(PyFunction_EVENT_MODIFY_QUALNAME, (PyFunctionObject *) op, value);
-    Py_XSETREF(op->func_qualname, Py_NewRef(value));
+    handle_func_event(PyFunction_EVENT_MODIFY_QUALNAME, self, value);
+    Py_XSETREF(self->func_qualname, Py_NewRef(value));
     return 0;
 }
 
@@ -976,8 +1000,8 @@ static PyGetSetDef func_getsetlist[] = {
     FUNCTION___ANNOTATIONS___GETSETDEF
     FUNCTION___ANNOTATE___GETSETDEF
     {"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict},
-    {"__name__", func_get_name, func_set_name},
-    {"__qualname__", func_get_qualname, func_set_qualname},
+    FUNCTION___NAME___GETSETDEF
+    FUNCTION___QUALNAME___GETSETDEF
     FUNCTION___TYPE_PARAMS___GETSETDEF
     {NULL} /* Sentinel */
 };
@@ -1147,8 +1171,12 @@ static PyObject*
 func_repr(PyObject *self)
 {
     PyFunctionObject *op = _PyFunction_CAST(self);
-    return PyUnicode_FromFormat("<function %U at %p>",
-                                op->func_qualname, op);
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(self);
+    result = PyUnicode_FromFormat("<function %U at %p>",
+                                  op->func_qualname, op);
+    Py_END_CRITICAL_SECTION();
+    return result;
 }
 
 static int
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix data race on assigning ``__name__`` and ``__qualname__`` attrs to
		function objects on FT builds.