[3.14] gh-145446: Add critical section in functools module for PyDict_Next (GH-145487) (GH-145879)

(cherry picked from commit 17eb035)

Author: bkap123

Misc/NEWS.d/next/Library/2026-03-03-23-21-40.gh-issue-145446.0c-TJX.rst

@@ -0,0 +1 @@
+Now :mod:`functools` is safer in free-threaded build when using keywords in :func:`functools.partial`

Modules/_functoolsmodule.c

@@ -646,16 +646,23 @@ partial_repr(PyObject *self)
         }
     }
     /* Pack keyword arguments */
+    int error = 0;
+    Py_BEGIN_CRITICAL_SECTION(kw);
     for (i = 0; PyDict_Next(kw, &i, &key, &value);) {
         /* Prevent key.__str__ from deleting the value. */
         Py_INCREF(value);
         Py_SETREF(arglist, PyUnicode_FromFormat("%U, %S=%R", arglist,
                                                 key, value));
         Py_DECREF(value);
         if (arglist == NULL) {
-            goto done;
+            error = 1;
+            break;
         }
     }
+    Py_END_CRITICAL_SECTION();
+    if (error) {
+        goto done;
+    }
 
     mod = PyType_GetModuleName(Py_TYPE(pto));
     if (mod == NULL) {