Hi, On 18/11/14 02:32, Wanpeng Li wrote: > Queued ticks are scheduled to match the budget, which means the budget > is overall consumed and the dl task should be throttled. > > Dl task will be replenished immediately if fail to start a dl timer. > So the curr maybe not the left most dl task in the rb tree any more > after this immediately replenished since reschedule is needed. > > The parameter of task_tick_dl() queued == 1 means that hrtick is fired. > hrtick() => task_tick_dl( , ,1), so p->dl.runtime should be <= 0 if > queued == 1. If replenished immediately(fail to start dl timer), > hrtick is start for task w/ queued == 1 && p->dl.runtime > 0 && p is > not the left most task. > > Start high-res preemption tick for this upcoming rescheduled dl task > is not correct. This patch fix it by not starting high-res preemption > tick for a non-leftmost dl task. > > Signed-off-by: Wanpeng Li <[email protected]> > --- > v1 -> v2: > * add a more explanatory changelog > * add a comment just above the check > > kernel/sched/deadline.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index e5db8c6..981479a 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -1090,7 +1090,18 @@ static void task_tick_dl(struct rq *rq, struct > task_struct *p, int queued) > { > update_curr_dl(rq); > > - if (hrtick_enabled(rq) && queued && p->dl.runtime > 0) > + /* > + * Queued tick means that hrtick is fired, when the budget is > + * consumed the task has to be throttled. However, task will > + * be replenished immediately if fail to start a dl timer, in > + * addition, the task maybe not the left most any more. Don't > + * start high-res preemption tick for the task who is not the > + * left most. The high-res preemption tick will be started for > + * this task just when it can be picked in pick_next_task_dl() > + * again. > + */ > + if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 && > + is_leftmost(p, &rq->dl)) > start_hrtick_dl(rq, p); > } > >
Acked-by: Juri Lelli <[email protected]> Thanks, - Juri -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
