Re: [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up()

[Kirill Tkhai]

25.08.2014, 20:01, "Oleg Nesterov" <oleg@xxxxxxxxxx>:
> Peter, do you remember another problem with TASK_DEAD we discussed recently?
> (prev_state == TASK_DEAD detection in finish_task_switch() still looks racy).

One more problem with task_dead just to mention it here.

Below is racy with the change of sched_class:

        if (prev->sched_class->task_dead)
                prev->sched_class->task_dead(prev);

switched_from_dl() does not cancel running timers.

So, if dl_task_timer() is slow (it is unhappy with rq->lock acquiring),
the timer is executing when tasks is already dead.

Kirill
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