Re: kernel BUG at kernel/sched/core.c:3490!

[Oleg Nesterov <oleg@redhat.com>]

On 01/12, Kohli, Gaurav wrote:
>
> HI Peter, Oleg,
>
> as per flag and state this seems to be possible only from below code:

Not sure I understand you,

> XXX: 0 1 0x40844c
> PF_NOFREEZE
> PF_RANDOMIZE
> PF_SIGNALED
> PF_FORKNOEXEC
> PF_EXITING
> PF_EXITPIDONE
>
> above state shows do_exit runs properely and  if somehow after parked stated
> , TASK_WAKEKILL got set and signal_pending_state returns 1 in below case:
>
>  switch_count = &prev->nivcsw;
>         if (!preempt && prev->state) {
>                 if (unlikely(signal_pending_state(prev->state, prev))) {
>                         prev->state = TASK_RUNNING;
>                 } else {
>                         deactivate_task(rq, prev, DEQUEUE_SLEEP |
> DEQUEUE_NOCLOCK);

or task->state was TASK_RUNNING when __schedule() was called, or the deactivated
dead task was woken up later...

The only problem is that every case looks "obviously impossible" ;) I have no
idea whats going on, I can only suggest more stupid debugging patches which might
narrow the problem.

Oleg.