Merged revisions 76119 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/branches/py3k

................
  r76119 | antoine.pitrou | 2009-11-05 14:49:14 +0100 (jeu., 05 nov. 2009) | 10 lines

  Merged revisions 76117 via svnmerge from
  svn+ssh://pythondev@svn.python.org/python/trunk

  ........
    r76117 | antoine.pitrou | 2009-11-05 14:42:29 +0100 (jeu., 05 nov. 2009) | 5 lines

    Issue #7264: Fix a possible deadlock when deallocating thread-local objects
    which are part of a reference cycle.
  ........
................

Lib/_threading_local.py

@@ -217,10 +217,12 @@ def __del__(self):
         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
 

Lib/threading.py

@@ -798,6 +798,10 @@ def active_count():
 
 activeCount = active_count
 
+def _enumerate():
+    # Same as enumerate(), but without the lock. Internal use only.
+    return list(_active.values()) + list(_limbo.values())
+
 def enumerate():
     with _active_limbo_lock:
         return list(_active.values()) + list(_limbo.values())

Misc/NEWS

@@ -40,6 +40,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #7264: Fix a possible deadlock when deallocating thread-local objects
+  which are part of a reference cycle.
+
 - Issue #6896: mailbox.Maildir now invalidates its internal cache each time
   a modification is done through it.  This fixes inconsistencies and test
   failures on systems with slightly bogus mtime behaviour.