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Date: Mon, 16 Mar 2015 21:00:43 +0100
From: Philippe Gerum <rpm@xenomai.org>
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Subject: Re: [Xenomai] Xenomai 3: smokey test sched_tp causes oops when run
	in gdb
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To: Jan Kiszka <jan.kiszka@siemens.com>, Xenomai <xenomai@xenomai.org>

On 03/16/2015 08:44 PM, Jan Kiszka wrote:
> On 2015-03-16 20:41, Philippe Gerum wrote:
>> On 03/16/2015 08:35 PM, Jan Kiszka wrote:
>>> On 2015-03-16 20:24, Philippe Gerum wrote:
>>>> On 03/16/2015 06:16 PM, Jan Kiszka wrote:
>>>>> Don't understand the reason for this multiple calls in details yet, but
>>>>> you can also trigger the bug by invoking pthread_setschedparam_ex twice
>>>>> in smokey's sched-tp.c. Fix pushed to for-forge.
>>>>>
>>>>
>>>> This is what has to be fixed, because guarding would only paper over the
>>>> issue for TP, but the latter would bite the same way with other existing
>>>> or future policies.
>>>
>>> You mean push the guard into xnsched_set_policy, e.g.?
>>>
>>
>> Or fix what might be a signal restart issue so that we don't end up
>> twice in xnsched_set_policy().
> 
> Again, already calling pthread_setschedparam_ex twice in a row on the
> same thread triggers the bug. There is no way around such a guard.
> 

Then yes, the proper fix should be pushed to xnsched_set_policy() instead:

diff --git a/kernel/cobalt/sched.c b/kernel/cobalt/sched.c
index a6469db..093e3be 100644
--- a/kernel/cobalt/sched.c
+++ b/kernel/cobalt/sched.c
@@ -387,9 +387,11 @@ int xnsched_set_policy(struct xnthread *thread,
 	 * affect the previous class (such as touching thread->rlink
 	 * for instance).
 	 */
-	ret = xnsched_declare(sched_class, thread, p);
-	if (ret)
-		return ret;
+	if (sched_class != thread->base_class) {
+		ret = xnsched_declare(sched_class, thread, p);
+		if (ret)
+			return ret;
+	}

 	/*
 	 * As a special case, we may be called from __xnthread_init()

-- 
Philippe.