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    SubjectRe: [PATCH 01/16] sched: add sched_class->task_dead.
    On 04/06, Juri Lelli wrote:
    >
    > --- a/kernel/sched.c
    > +++ b/kernel/sched.c
    > @@ -3219,6 +3219,9 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
    > if (mm)
    > mmdrop_delayed(mm);
    > if (unlikely(prev_state == TASK_DEAD)) {
    > + if (prev->sched_class->task_dead)
    > + prev->sched_class->task_dead(prev);
    > +

    And 5/16 adds

    +static void task_dead_dl(struct task_struct *p)
    +{
    + struct hrtimer *timer = &p->dl.dl_timer;
    +
    + if (hrtimer_active(timer))
    + hrtimer_try_to_cancel(timer);
    +}

    This looks suspicious. finish_task_switch() does put_task_struct()
    after that, it is quite possible this actually frees the memory.

    What if hrtimer_try_to_cancel() fails because the timer is running?
    In this case __run_hrtimer() can play with the freed timer. Say, to
    clear HRTIMER_STATE_CALLBACK. Not to mention dl_task_timer() itself.

    Oleg.



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