Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754708AbaKRRak (ORCPT ); Tue, 18 Nov 2014 12:30:40 -0500 Received: from service87.mimecast.com ([91.220.42.44]:33928 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754413AbaKRRah convert rfc822-to-8bit (ORCPT ); Tue, 18 Nov 2014 12:30:37 -0500 Message-ID: <546B8251.5080805@arm.com> Date: Tue, 18 Nov 2014 17:30:57 +0000 From: Juri Lelli User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Wanpeng Li , Ingo Molnar , Peter Zijlstra CC: Kirill Tkhai , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2] sched/deadline: fix start high-res preemption tick for a non-leftmost task References: <1416277974-11962-1-git-send-email-wanpeng.li@linux.intel.com> In-Reply-To: <1416277974-11962-1-git-send-email-wanpeng.li@linux.intel.com> X-OriginalArrivalTime: 18 Nov 2014 17:30:32.0754 (UTC) FILETIME=[5AFF7920:01D00355] X-MC-Unique: 114111817303413701 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 Thanks, - Juri -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/