Issue #14548: Make multiprocessing finalizers check pid before

running to cope with possibility of gc running just after fork.
(Backport from 3.x.)

Lib/multiprocessing/util.py

@@ -32,6 +32,7 @@
 # SUCH DAMAGE.
 #
 
+import os
 import itertools
 import weakref
 import atexit
@@ -184,6 +185,7 @@ class Finalize(object):
         self._args = args
         self._kwargs = kwargs or {}
         self._key = (exitpriority, _finalizer_counter.next())
+        self._pid = os.getpid()
 
         _finalizer_registry[self._key] = self
 
@@ -196,9 +198,13 @@ class Finalize(object):
         except KeyError:
             sub_debug('finalizer no longer registered')
         else:
-            sub_debug('finalizer calling %s with args %s and kwargs %s',
-                     self._callback, self._args, self._kwargs)
-            res = self._callback(*self._args, **self._kwargs)
+            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)
+                res = self._callback(*self._args, **self._kwargs)
             self._weakref = self._callback = self._args = \
                             self._kwargs = self._key = None
             return res

Misc/NEWS

@@ -38,6 +38,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #14548: Make multiprocessing finalizers check pid before
+  running to cope with possibility of gc running just after fork.
+  (Backport from 3.x.)
+
 - Issue #20262: Warnings are raised now when duplicate names are added in the
   ZIP file or too long ZIP file comment is truncated.