[3.7] bpo-42406: Fix whichmodule() with multiprocessing (pythonGH-23403)

faucct · web-flow · commit 3eb809577439 · 2021-09-21T14:16:27.000+03:00
diff --git a/Lib/pickle.py b/Lib/pickle.py
@@ -307,7 +307,9 @@ def whichmodule(obj, name):
     # Protect the iteration by using a list copy of sys.modules against dynamic
     # modules that trigger imports of other modules upon calls to getattr.
     for module_name, module in list(sys.modules.items()):
-        if module_name == '__main__' or module is None:
+        if (module_name == '__main__'
+             or module_name == '__mp_main__'  # bpo-42406
+             or module is None):
             continue
         try:
             if _getattribute(module, name)[0] is obj:
