merge 3.4-slp (Stackless python#123)

Author: Anselm Kruis

Stackless/changelog.txt

@@ -9,6 +9,10 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://bitbucket.org/stackless-dev/stackless/issues/123
+  Fix a rare assertion violation during interpreter shutdown with active
+  daemon threads.
+
 - https://bitbucket.org/stackless-dev/stackless/issues/122
   Disable the C-stack cache, if Py_REF_DEBUG is defined. The cache causes false
   block leak errors from the test suite. The performance penalty is irrelevant in

Stackless/module/taskletobject.c

@@ -46,8 +46,12 @@ slp_current_remove(void)
     PyThreadState *ts = PyThreadState_GET();
     PyTaskletObject **chain = &ts->st.current, *ret;
 
-    /* make sure tasklet belongs to this thread */
-    assert((*chain)->cstate->tstate == ts);
+    /* Make sure that the tasklet belongs to this thread.
+     * During interpreter shutdown '(*chain)->cstate->tstate' may be already NULL.
+     * See function slp_kill_tasks_with_stacks() in stacklesseval.c
+     */
+    assert((*chain)->cstate->tstate == ts ||
+           (*chain)->cstate->tstate == NULL);
 
     --ts->st.runcount;
     assert(ts->st.runcount >= 0);