#Issue3088 in-progress: Race condition with instances of classes derived from threading.local: When a thread touches such an object for the first time, a new thread-local __dict__ is created, and the __init__ method is run. But a thread switch can occur here; if the other thread touches the same object, it installs another __dict__; when the first thread resumes, it updates the dictionary of the second... This is the deep cause of the failures in test_multiprocessing involving "managers" objects. Also a 2.5 backport candidate.

--- a/Modules/threadmodule.c	Mon Jun 30 07:01:09 2008 +0000
+++ b/Modules/threadmodule.c	Mon Jun 30 22:42:40 2008 +0000
@@ -293,7 +293,10 @@
 		}
 		
 	}
-	else if (self->dict != ldict) {
+
+	/* The call to tp_init above may have caused another thread to run.
+	   Install our ldict again. */
+	if (self->dict != ldict) {
 		Py_CLEAR(self->dict);
 		Py_INCREF(ldict);
 		self->dict = ldict;