Author: philip.jenvey Date: Tue Sep 29 06:32:44 2009 New Revision: 75123 Log: #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/trunk/Lib/test/test_threading_local.py python/trunk/Misc/NEWS python/trunk/Modules/threadmodule.c Modified: python/trunk/Lib/test/test_threading_local.py ============================================================================== --- python/trunk/Lib/test/test_threading_local.py (original) +++ python/trunk/Lib/test/test_threading_local.py Tue Sep 29 06:32:44 2009 @@ -67,6 +67,44 @@ 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(): + # 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[0] = 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[0]) + def test_main(): suite = unittest.TestSuite() Modified: python/trunk/Misc/NEWS ============================================================================== --- python/trunk/Misc/NEWS (original) +++ python/trunk/Misc/NEWS Tue Sep 29 06:32:44 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 #6300: unicode.encode, unicode.decode, str.decode, and str.encode now take keyword arguments. Modified: python/trunk/Modules/threadmodule.c ============================================================================== --- python/trunk/Modules/threadmodule.c (original) +++ python/trunk/Modules/threadmodule.c Tue Sep 29 06:32:44 2009 @@ -244,7 +244,6 @@ static int local_clear(localobject *self) { - Py_CLEAR(self->key); Py_CLEAR(self->args); Py_CLEAR(self->kw); Py_CLEAR(self->dict); @@ -266,6 +265,7 @@ PyDict_DelItem(tstate->dict, self->key); } + Py_XDECREF(self->key); local_clear(self); Py_TYPE(self)->tp_free((PyObject*)self); }