> * Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
>
>> On Sun, Jun 29, 2008 at 12:16:56AM +0200, Dmitry Adamushko wrote:
>>> Hello,
>>>
>>>
>>> it seems to be related to migrate_dead_tasks().
>>>
>>> Firstly I added traces to see all tasks being migrated with
>>> migrate_live_tasks() and migrate_dead_tasks(). On my setup the problem
>>> pops up (the one with "se == NULL" in the loop of
>>> pick_next_task_fair()) shortly after the traces indicate that some has
>>> been migrated with migrate_dead_tasks()). btw., I can reproduce it
>>> much faster now with just a plain cpu down/up loop.
>>>
>>> [disclaimer] Well, unless I'm really missing something important in
>>> this late hour [/desclaimer] pick_next_task() is not something
>>> appropriate for migrate_dead_tasks() :-)
>>>
>>> the following change seems to eliminate the problem on my setup
>>> (although, I kept it running only for a few minutes to get a few
>>> messages indicating migrate_dead_tasks() does move tasks and the
>>> system is still ok)
>>>
>>> [ quick hack ]
>>>
>>> @@ -5887,6 +5907,7 @@ static void migrate_dead_tasks(unsigned int dead_cpu)
>>> next = pick_next_task(rq, rq->curr);
>>> if (!next)
>>> break;
>>> + next->sched_class->put_prev_task(rq, next);
>>> migrate_dead(dead_cpu, next);
>>>
>>> }
>> Thanks Dmitry! With your patch I cannot reproduce the bug anymore.
>
> thanks - it passed my testing too. It's lined up for v2.6.26 merge, in
> tip/sched/urgent.
>
> Avi, does this patch fix your CPU hotplug problems too?
>
> Ingo
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