Re: [Xenomai-help] Re: Re: What happens if task entry function returns?

[Philippe Gerum <rpm@xenomai.org>]

On Fri, 2006-11-17 at 15:17 +0100, M. Koehrer wrote:
> Hi Jan, 
> 
> First, I give you some more information about the error.
> The output is the following:
> Hi, I am task A Hello
> Hi, I am task B World
> Main waits for A
> This is the end of A
> Main waits for B
> 
> Then the system hangs.
> 

Confirmed here on a two-way PIII. Well, _this_ was a nice one.
Basically, the softlock was due to a missing rescheduling call after
task A has exited, leaving task B in ready state, somewhere in the
Twilight Zone. The patch below fixes it on my setup:

--- ksrc/nucleus/shadow.c	(revision 1854)
+++ ksrc/nucleus/shadow.c	(working copy)
@@ -1631,7 +1631,8 @@
 
 static inline void do_taskexit_event(struct task_struct *p)
 {
-	xnthread_t *thread = xnshadow_thread(p);	/* p == current */
+	xnthread_t *thread = xnshadow_thread(p); /* p == current */
+	spl_t s;
 
 	if (!thread)
 		return;
@@ -1639,12 +1640,15 @@
 	if (xnpod_shadow_p())
 		xnshadow_relax(0);
 
-	/* So that we won't attempt to further wakeup the exiting task in
-	   xnshadow_unmap(). */
-
+	xnlock_get_irqsave(&nklock, s);
+	/* Prevent wakeup call from xnshadow_unmap(). */
 	xnshadow_thrptd(p) = NULL;
 	xnthread_archtcb(thread)->user_task = NULL;
-	xnpod_delete_thread(thread);	/* Should indirectly call xnshadow_unmap(). */
+	/* xnpod_delete_thread() -> hook -> xnshadow_unmap(). */
+	xnpod_delete_thread(thread);
+	xnsched_set_resched(thread->sched);
+	xnpod_schedule();
+	xnlock_put_irqrestore(&nklock, s);
 
 	xnltt_log_event(xeno_ev_shadowexit, thread->name);
 }

-- 
Philippe.