[Python-checkins] r75126 - in python/branches/release31-maint: Lib/test/test_threading_local.py Misc/NEWS Modules/_threadmodule.c

[philip.jenvey]

Author: philip.jenvey
Date: Tue Sep 29 07:03:48 2009
New Revision: 75126

Log:
Merged revisions 75125 via svnmerge from 
svn+ssh://pythondev@svn.python.org/python/branches/py3k

................
  r75125 | philip.jenvey | 2009-09-28 21:57:18 -0700 (Mon, 28 Sep 2009) | 11 lines
  
  Recorded merge of revisions 75123 via svnmerge from 
  svn+ssh://pythondev@svn.python.org/python/trunk
  
  ........
    r75123 | philip.jenvey | 2009-09-28 21:32:44 -0700 (Mon, 28 Sep 2009) | 4 lines
    
    #6990: clear threading.local's key only after its thread state is removed:
    fixes local subclasses leaving old state around after a ref cycle GC which
    could be recycled by new locals
  ........
................


Modified:
   python/branches/release31-maint/   (props changed)
   python/branches/release31-maint/Lib/test/test_threading_local.py
   python/branches/release31-maint/Misc/NEWS
   python/branches/release31-maint/Modules/_threadmodule.c

Modified: python/branches/release31-maint/Lib/test/test_threading_local.py
==============================================================================
--- python/branches/release31-maint/Lib/test/test_threading_local.py	(original)
+++ python/branches/release31-maint/Lib/test/test_threading_local.py	Tue Sep 29 07:03:48 2009
@@ -67,6 +67,45 @@
         for t in threads:
             t.join()
 
+    def test_derived_cycle_dealloc(self):
+        # http://bugs.python.org/issue6990
+        class Local(threading.local):
+            pass
+        locals = None
+        passed = False
+        e1 = threading.Event()
+        e2 = threading.Event()
+
+        def f():
+            nonlocal passed
+            # 1) Involve Local in a cycle
+            cycle = [Local()]
+            cycle.append(cycle)
+            cycle[0].foo = 'bar'
+
+            # 2) GC the cycle (triggers threadmodule.c::local_clear
+            # before local_dealloc)
+            del cycle
+            gc.collect()
+            e1.set()
+            e2.wait()
+
+            # 4) New Locals should be empty
+            passed = all(not hasattr(local, 'foo') for local in locals)
+
+        t = threading.Thread(target=f)
+        t.start()
+        e1.wait()
+
+        # 3) New Locals should recycle the original's address. Creating
+        # them in the thread overwrites the thread state and avoids the
+        # bug
+        locals = [Local() for i in range(10)]
+        e2.set()
+        t.join()
+
+        self.assertTrue(passed)
+
 
 def test_main():
     suite = unittest.TestSuite()

Modified: python/branches/release31-maint/Misc/NEWS
==============================================================================
--- python/branches/release31-maint/Misc/NEWS	(original)
+++ python/branches/release31-maint/Misc/NEWS	Tue Sep 29 07:03:48 2009
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #6990: Fix threading.local subclasses leaving old state around
+  after a reference cycle GC which could be recycled by new locals.
+
 - Issue #6846: Fix bug where bytearray.pop() returns negative integers.
 
 - Issue #6750: A text file opened with io.open() could duplicate its output

Modified: python/branches/release31-maint/Modules/_threadmodule.c
==============================================================================
--- python/branches/release31-maint/Modules/_threadmodule.c	(original)
+++ python/branches/release31-maint/Modules/_threadmodule.c	Tue Sep 29 07:03:48 2009
@@ -239,7 +239,6 @@
 static int
 local_clear(localobject *self)
 {
-	Py_CLEAR(self->key);
 	Py_CLEAR(self->args);
 	Py_CLEAR(self->kw);
 	Py_CLEAR(self->dict);
@@ -261,6 +260,7 @@
 				PyDict_DelItem(tstate->dict, self->key);
 	}
 
+	Py_XDECREF(self->key);
 	local_clear(self);
 	Py_TYPE(self)->tp_free((PyObject*)self);
 }