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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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