Issue #28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.
diff --git a/Lib/multiprocessing/spawn.py b/Lib/multiprocessing/spawn.py
index 4d76951..392c1599 100644
--- a/Lib/multiprocessing/spawn.py
+++ b/Lib/multiprocessing/spawn.py
@@ -218,7 +218,7 @@
process.ORIGINAL_DIR = data['orig_dir']
if 'start_method' in data:
- set_start_method(data['start_method'])
+ set_start_method(data['start_method'], force=True)
if 'init_main_from_name' in data:
_fixup_main_from_name(data['init_main_from_name'])