Issue #28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

2 files changed, 2 insertions, 2 deletions

diff --git a/Lib/multiprocessing/context.py b/Lib/multiprocessing/context.py
index 09455e2ec7..623f6fb733 100644
--- a/Lib/multiprocessing/context.py
+++ b/Lib/multiprocessing/context.py
@@ -196,7 +196,7 @@ class BaseContext(object):
     def get_start_method(self, allow_none=False):
         return self._name
 
-    def set_start_method(self, method=None):
+    def set_start_method(self, method, force=False):
         raise ValueError('cannot set start method of concrete context')
 
     @property
diff --git a/Lib/multiprocessing/spawn.py b/Lib/multiprocessing/spawn.py
index dfb9f65270..4aba372e48 100644
--- a/Lib/multiprocessing/spawn.py
+++ b/Lib/multiprocessing/spawn.py
@@ -217,7 +217,7 @@ def prepare(data):
         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'])