Re: [BUG] TASK_DEAD task is able to be woken up in specialcondition

[Peter Zijlstra]

On Wed, 2011-12-28 at 16:07 -0500, KOSAKI Motohiro wrote:
> I looked at scheduler code today briefly. now I'm afraid following code 
> have similar race.
> 
> 
>          if (task_contributes_to_load(p))
>                  rq->nr_uninterruptible--;
> 
> 
> 
> Can't following schenario be happen?
> 
> 
> CPU0                    CPU1
> --------------------------------------------------------
> deactivate_task()
>                         task->state = TASK_UNINTERRUPTIBLE;
> activate_task()
>    rq->nr_uninterruptible--;
> 
>                         schedule()
>                           deactivate_task()
>                             rq->nr_uninterruptible++;
> 
> Totally, nr_uninterruptible wasn't incremented.
> 
> 
> I'm still not sure. I need to read more sched code. 

You shouldn't ever set another tasks ->state. 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/