From cc6a7babd4bfbcb3b6fa958737a8eb15dc77012c Mon Sep 17 00:00:00 2001
From: "antoine.pitrou" <antoine.pitrou@6015fed2-1504-0410-9fe1-9d1591cc4771>
Date: Thu, 5 Nov 2009 13:42:29 +0000
Subject: [PATCH] Issue #7264: Fix a possible deadlock when deallocating
 thread-local objects which are part of a reference cycle.

git-svn-id: http://svn.python.org/projects/python/trunk@76117 6015fed2-1504-0410-9fe1-9d1591cc4771
---
 Lib/_threading_local.py | 8 +++++---
 Lib/threading.py        | 4 ++++
 Misc/NEWS               | 3 +++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/Lib/_threading_local.py b/Lib/_threading_local.py
index 4eda630bbd..243d84ef7c 100644
--- a/Lib/_threading_local.py
+++ b/Lib/_threading_local.py
@@ -218,10 +218,12 @@ class local(_localbase):
         key = object.__getattribute__(self, '_local__key')
 
         try:
-            threads = list(threading.enumerate())
+            # We use the non-locking API since we might already hold the lock
+            # (__del__ can be called at any point by the cyclic GC).
+            threads = threading._enumerate()
         except:
-            # If enumerate fails, as it seems to do during
-            # shutdown, we'll skip cleanup under the assumption
+            # If enumerating the current threads fails, as it seems to do
+            # during shutdown, we'll skip cleanup under the assumption
             # that there is nothing to clean up.
             return
 
diff --git a/Lib/threading.py b/Lib/threading.py
index cf20152b4d..9ad5122c8f 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -810,6 +810,10 @@ def activeCount():
 
 active_count = activeCount
 
+def _enumerate():
+    # Same as enumerate(), but without the lock. Internal use only.
+    return _active.values() + _limbo.values()
+
 def enumerate():
     with _active_limbo_lock:
         return _active.values() + _limbo.values()
diff --git a/Misc/NEWS b/Misc/NEWS
index 183aa7a588..8ae9afba4f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -426,6 +426,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #7264: Fix a possible deadlock when deallocating thread-local objects
+  which are part of a reference cycle.
+
 - Issue #7211: Allow 64-bit values for the `ident` and `data` fields of kevent
   objects on 64-bit systems.  Patch by Michael Broghton.
 
-- 
2.11.4.GIT