From 5c10c365fef3ca480c930cb379bf1d0ebadcd911 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Thu, 16 Jun 2022 07:07:30 -0700
Subject: [PATCH] gh-91577: SharedMemory move imports out of methods (GH-91579)

SharedMemory.unlink() uses the unregister() function from resource_tracker. Previously it was imported in the method, but this can fail if the method is called during interpreter shutdown, for example when unlink is part of a __del__() method.

Moving the import to the top of the file, means that the unregister() method is available during interpreter shutdown.

The register call in SharedMemory.__init__() can also use this imported resource_tracker.
(cherry picked from commit 9a458befdd68625d088f4fea7df135a57d147deb)

Co-authored-by: samtygier <samtygier@yahoo.co.uk>
---
 Lib/multiprocessing/shared_memory.py                       | 7 +++----
 .../Library/2022-04-15-17-38-55.gh-issue-91577.Ah7cLL.rst  | 1 +
 2 files changed, 4 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2022-04-15-17-38-55.gh-issue-91577.Ah7cLL.rst

diff --git a/Lib/multiprocessing/shared_memory.py b/Lib/multiprocessing/shared_memory.py
index 122b3fcebf3fed..881f2001dd5980 100644
--- a/Lib/multiprocessing/shared_memory.py
+++ b/Lib/multiprocessing/shared_memory.py
@@ -23,6 +23,7 @@
     import _posixshmem
     _USE_POSIX = True
 
+from . import resource_tracker
 
 _O_CREX = os.O_CREAT | os.O_EXCL
 
@@ -116,8 +117,7 @@ def __init__(self, name=None, create=False, size=0):
                 self.unlink()
                 raise
 
-            from .resource_tracker import register
-            register(self._name, "shared_memory")
+            resource_tracker.register(self._name, "shared_memory")
 
         else:
 
@@ -237,9 +237,8 @@ def unlink(self):
         called once (and only once) across all processes which have access
         to the shared memory block."""
         if _USE_POSIX and self._name:
-            from .resource_tracker import unregister
             _posixshmem.shm_unlink(self._name)
-            unregister(self._name, "shared_memory")
+            resource_tracker.unregister(self._name, "shared_memory")
 
 
 _encoding = "utf8"
diff --git a/Misc/NEWS.d/next/Library/2022-04-15-17-38-55.gh-issue-91577.Ah7cLL.rst b/Misc/NEWS.d/next/Library/2022-04-15-17-38-55.gh-issue-91577.Ah7cLL.rst
new file mode 100644
index 00000000000000..0f44f34011f9c7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-04-15-17-38-55.gh-issue-91577.Ah7cLL.rst
@@ -0,0 +1 @@
+Move imports in :class:`~multiprocessing.SharedMemory` methods to module level so that they can be executed late in python finalization.