Fix the tests.

Author: ZeroIntensity

Lib/test/test_atexit.py

@@ -52,10 +52,6 @@ def test_atexit_instances(self):
     @unittest.skipUnless(support.Py_GIL_DISABLED, "only meaningful without the GIL")
     def test_atexit_thread_safety(self):
         # GH-126907: atexit was not thread safe on the free-threaded build
-
-        # I'm not certain this needs to be in a script runner, but
-        # let's do it anyway.
-        code = textwrap.dedent("""
         from threading import Thread
 
         def dummy():
@@ -70,10 +66,9 @@ def thready():
                 atexit.unregister(dummy)
 
 
-        for x in range(100):
-            Thread(target=thready, args=()).start()
-        """)
-        script_helper.assert_python_ok("-c", code)
+        threads = [Thread(target=thready) for _ in range(100)]
+        with threading_helper.start_threads(threads):
+            pass
 
 
 @support.cpython_only

Modules/atexitmodule.c

@@ -62,9 +62,12 @@ atexit_delete_cb(struct atexit_state *state, int i)
     atexit_py_callback *cb = state->callbacks[i];
     state->callbacks[i] = NULL;
 
+    // This can execute code via finalizers
+    _PyAtExit_UNLOCK(state);
     Py_DECREF(cb->func);
     Py_DECREF(cb->args);
     Py_XDECREF(cb->kwargs);
+    _PyAtExit_LOCK(state);
     PyMem_Free(cb);
 }
 
@@ -143,8 +146,12 @@ atexit_callfuncs(struct atexit_state *state)
         }
 
         // bpo-46025: Increment the refcount of cb->func as the call itself may unregister it
-        PyObject* the_func = Py_NewRef(cb->func);
-        PyObject *res = PyObject_Call(cb->func, cb->args, cb->kwargs);
+        PyObject *the_func = Py_NewRef(cb->func);
+        PyObject *the_args = cb->args;
+        PyObject *the_kwargs = cb->kwargs;
+        // Unlock for re-entrancy problems
+        _PyAtExit_UNLOCK(state);
+        PyObject *res = PyObject_Call(the_func, the_args, the_kwargs);
         if (res == NULL) {
             PyErr_FormatUnraisable(
                 "Exception ignored in atexit callback %R", the_func);
@@ -153,6 +160,7 @@ atexit_callfuncs(struct atexit_state *state)
             Py_DECREF(res);
         }
         Py_DECREF(the_func);
+        _PyAtExit_LOCK(state);
     }
 
     atexit_cleanup(state);