Re: [RFC v2 3/7] Improve the tracking of active utilisation

Peter Zijlstra
2016-04-05T12:42:59Z

On Fri, Apr 01, 2016 at 05:12:29PM +0200, Luca Abeni wrote:
> @@ -526,7 +575,18 @@ static void update_dl_entity(struct sched_dl_entity *dl_se,
> struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> struct rq *rq = rq_of_dl_rq(dl_rq);
>
> - add_running_bw(dl_se, dl_rq);
> + /*
> + * If the "inactive timer" is still active, stop it and leave
> + * the active utilisation unchanged.
> + * Otherwise, increase the active utilisation.
> + * If the timer cannot be cancelled, inactive_task_timer() will
> + * find the task state as TASK_RUNNING, and will do nothing, so
> + * we are still safe.
> + */
> + if (hrtimer_active(&dl_se->inactive_timer))
> + hrtimer_try_to_cancel(&dl_se->inactive_timer);

_try_, what happens if that fails?

> + else
> + add_running_bw(dl_se, dl_rq);
>
> if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
> dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {