[3.10] bpo-45021: Fix a hang in forked children (GH-28007) (GH-28480)

[3.10] bpo-45021: Fix a hang in forked children (GH-28007) (GH-28480) · python/cpython@d0d83a9

Original file line number	Diff line number	Diff line change
`@@ -36,6 +36,12 @@ def _python_exit():`
`36`	`36`	`# See bpo-39812 for context.`
`37`	`37`	`threading._register_atexit(_python_exit)`
`38`	`38`
	`39`	+# At fork, reinitialize the `_global_shutdown_lock` lock in the child process
	`40`	`+if hasattr(os, 'register_at_fork'):`
	`41`	`+os.register_at_fork(before=_global_shutdown_lock.acquire,`
	`42`	`+after_in_child=_global_shutdown_lock._at_fork_reinit,`
	`43`	`+after_in_parent=_global_shutdown_lock.release)`
	`44`	`+`
`39`	`45`
`40`	`46`	`class _WorkItem(object):`
`41`	`47`	`def __init__(self, future, fn, args, kwargs):`