Issue #14548: Make multiprocessing finalizers check pid before running

This protects from possibilty of gc running just after fork.

Lib/multiprocessing/util.py

@@ -9,6 +9,7 @@
 
 import sys
 import functools
+import os
 import itertools
 import weakref
 import atexit
@@ -161,6 +162,7 @@ class Finalize(object):
         self._args = args
         self._kwargs = kwargs or {}
         self._key = (exitpriority, next(_finalizer_counter))
+        self._pid = os.getpid()
 
         _finalizer_registry[self._key] = self
 
@@ -176,6 +178,10 @@ class Finalize(object):
             del _finalizer_registry[self._key]
         except KeyError:
             sub_debug('finalizer no longer registered')
+        else:
+            if self._pid != os.getpid():
+                sub_debug('finalizer ignored because different process')
+                res = None
             else:
                 sub_debug('finalizer calling %s with args %s and kwargs %s',
                           self._callback, self._args, self._kwargs)

Misc/NEWS

@@ -44,6 +44,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #14548: Make multiprocessing finalizers check pid before
+  running to cope with possibility of gc running just after fork.
+
 - Issue #14863: Update the documentation of os.fdopen() to reflect the
   fact that it's only a thin wrapper around open() anymore.