pythongh-121110: Fix Extension Module Tests Under Py_TRACE_REFS Builds (

pythongh-121503)

The change in pythongh-118157 (b2cd54a) should have also updated clear_singlephase_extension() but didn't.  We fix that here.  Note that clear_singlephase_extension() (AKA _PyImport_ClearExtension()) is only used in tests.

Lib/test/test_import/__init__.py

@@ -3034,13 +3034,6 @@ def test_basic_multiple_interpreters_deleted_no_reset(self):
  def test_basic_multiple_interpreters_reset_each(self):
  # resetting between each interpreter
 
- if Py_TRACE_REFS:
- # It's a Py_TRACE_REFS build.
- # This test breaks interpreter isolation a little,
- # which causes problems on Py_TRACE_REF builds.
- # See gh-121110.
- raise unittest.SkipTest('crashes on Py_TRACE_REFS builds')
-
  # At this point:
  # * alive in 0 interpreters
  # * module def may or may not be loaded already

Python/import.c

@@ -1532,6 +1532,35 @@ switch_to_main_interpreter(PyThreadState *tstate)
  return main_tstate;
 }
 
+static void
+switch_back_from_main_interpreter(PyThreadState *tstate,
+ PyThreadState *main_tstate,
+ PyObject *tempobj)
+{
+ assert(main_tstate == PyThreadState_GET());
+ assert(_Py_IsMainInterpreter(main_tstate->interp));
+ assert(tstate->interp != main_tstate->interp);
+
+ /* Handle any exceptions, which we cannot propagate directly
+ * to the subinterpreter. */
+ if (PyErr_Occurred()) {
+ if (PyErr_ExceptionMatches(PyExc_MemoryError)) {
+ /* We trust it will be caught again soon. */
+ PyErr_Clear();
+ }
+ else {
+ /* Printing the exception should be sufficient. */
+ PyErr_PrintEx(0);
+ }
+ }
+
+ Py_XDECREF(tempobj);
+
+ PyThreadState_Clear(main_tstate);
+ (void)PyThreadState_Swap(tstate);
+ PyThreadState_Delete(main_tstate);
+}
+
 static PyObject *
 get_core_module_dict(PyInterpreterState *interp,
  PyObject *name, PyObject *path)
@@ -2027,27 +2056,10 @@ import_run_extension(PyThreadState *tstate, PyModInitFunction p0,
  /* Switch back to the subinterpreter. */
  if (switched) {
  assert(main_tstate != tstate);
-
- /* Handle any exceptions, which we cannot propagate directly
- * to the subinterpreter. */
- if (PyErr_Occurred()) {
- if (PyErr_ExceptionMatches(PyExc_MemoryError)) {
- /* We trust it will be caught again soon. */
- PyErr_Clear();
- }
- else {
- /* Printing the exception should be sufficient. */
- PyErr_PrintEx(0);
- }
- }
-
+ switch_back_from_main_interpreter(tstate, main_tstate, mod);
  /* Any module we got from the init function will have to be
  * reloaded in the subinterpreter. */
- Py_CLEAR(mod);
-
- PyThreadState_Clear(main_tstate);
- (void)PyThreadState_Swap(tstate);
- PyThreadState_Delete(main_tstate);
+ mod = NULL;
  }
 
  /*****************************************************************/
@@ -2141,9 +2153,21 @@ clear_singlephase_extension(PyInterpreterState *interp,
  }
  }
 
+ /* We must use the main interpreter to clean up the cache.
+ * See the note in import_run_extension(). */
+ PyThreadState *tstate = PyThreadState_GET();
+ PyThreadState *main_tstate = switch_to_main_interpreter(tstate);
+ if (main_tstate == NULL) {
+ return -1;
+ }
+
  /* Clear the cached module def. */
  _extensions_cache_delete(path, name);
 
+ if (main_tstate != tstate) {
+ switch_back_from_main_interpreter(tstate, main_tstate, NULL);
+ }
+
  return 0;
 }