changeset:   90124:b5c91b61991a
branch:      3.4
parent:      90121:8fe2bb0c5851
user:        Vinay Sajip <vinay_sajip@yahoo.co.uk>
date:        Fri Apr 04 10:51:49 2014 +0100
files:       Lib/logging/__init__.py Misc/NEWS
description:
Issue #21149: Improved thread-safety in logging cleanup during interpreter shutdown.


diff -r 8fe2bb0c5851 -r b5c91b61991a Lib/logging/__init__.py
--- a/Lib/logging/__init__.py	Thu Apr 03 08:01:22 2014 -0700
+++ b/Lib/logging/__init__.py	Fri Apr 04 10:51:49 2014 +0100
@@ -711,16 +711,17 @@
     Remove a handler reference from the internal cleanup list.
     """
     # This function can be called during module teardown, when globals are
-    # set to None. If _acquireLock is None, assume this is the case and do
-    # nothing.
-    if (_acquireLock is not None and _handlerList is not None and
-        _releaseLock is not None):
-        _acquireLock()
+    # set to None. It can also be called from another thread. So we need to
+    # pre-emptively grab the necessary globals and check if they're None,
+    # to prevent race conditions and failures during interpreter shutdown.
+    acquire, release, handlers = _acquireLock, _releaseLock, _handlerList
+    if acquire and release and handlers:
+        acquire()
         try:
-            if wr in _handlerList:
-                _handlerList.remove(wr)
+            if wr in handlers:
+                handlers.remove(wr)
         finally:
-            _releaseLock()
+            release()
 
 def _addHandlerRef(handler):
     """
diff -r 8fe2bb0c5851 -r b5c91b61991a Misc/NEWS
--- a/Misc/NEWS	Thu Apr 03 08:01:22 2014 -0700
+++ b/Misc/NEWS	Fri Apr 04 10:51:49 2014 +0100
@@ -27,6 +27,9 @@
 Library
 -------
 
+- Issue #21149: Improved thread-safety in logging cleanup during interpreter
+  shutdown. Thanks to Devin Jeanpierre for the patch.
+
 - Issue #20145: `assertRaisesRegex` and `assertWarnsRegex` now raise a
   TypeError if the second argument is not a string or compiled regex.