Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753116AbaKQLCa (ORCPT ); Mon, 17 Nov 2014 06:02:30 -0500 Received: from mail-pa0-f41.google.com ([209.85.220.41]:46204 "EHLO mail-pa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752720AbaKQLC0 (ORCPT ); Mon, 17 Nov 2014 06:02:26 -0500 Message-ID: <5469D5B2.8040009@gmail.com> Date: Mon, 17 Nov 2014 19:02:10 +0800 From: Wanpeng Li User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Juri Lelli , Wanpeng Li , Ingo Molnar , Peter Zijlstra CC: Kirill Tkhai , "linux-kernel@vger.kernel.org" , "juri.lelli@gmail.com" Subject: Re: [PATCH 2/2] sched/deadline: fix start high-res preemption tick for a non-running task References: <1415670747-58726-1-git-send-email-wanpeng.li@linux.intel.com> <1415670747-58726-2-git-send-email-wanpeng.li@linux.intel.com> <54647BDC.6050804@arm.com> <5464882D.40504@gmail.com> <5469C503.9010007@arm.com> In-Reply-To: <5469C503.9010007@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Juri, On 11/17/14, 5:50 PM, Juri Lelli wrote: > Hi, > > On 13/11/14 10:30, Wanpeng Li wrote: >> Hi Juri, >> On 11/13/14, 5:37 PM, Juri Lelli wrote: >>> Hi, >>> >>> not sure I understand what the problem is here. >>> >>> On 11/11/14 01:52, 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. >>> ... enforce the budget? It means that when the budget is consumed the >>> task has to be throttled... >> Agreed. >> >>>> Dl task will >>>> be replenished immediately if fail to start a dl timer. >>>> >>>> However, the curr maybe not the left most dl task in the rb tree any >>>> more after this immediately replenished and reschedule is needed. >>>> Start high-res preemption tick for this upcoming rescheduled dl task >>>> is not correct. >>>> >>> So, the task that is going to preempt curr is picked by >>> pick_next_task_dl(), that correctly starts the hrtick for this new task. >>> >>> Maybe you can add more information about what you are seeing? A callpath >>> maybe? >> 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. What I see is queued == 1 && p->dl.runtime > 0 && p is not >> the left most task and hrtick is start for this task. >> > Oh, right, now it makes sense. Good catch! :) > > Could you please post a second version with a more explanatory changelog > and maybe a comment just above the check? Ok, I will do it and send out a new version tomorrow. ;-) Btw, could you review this patch? https://lkml.org/lkml/2014/11/13/51 The bug is introduced by deadline. Regards, Wanpeng Li > > Thanks, > > - Juri > >> Regards, >> Wanpeng Li >> >>> Thanks, >>> >>> - Juri >>> >>>> This patch fix it by not starting high-res preemption tick for a >>>> non-running dl task. >>>> >>>> Signed-off-by: Wanpeng Li >>>> --- >>>> kernel/sched/deadline.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >>>> index 56674f6..2a6a5bb 100644 >>>> --- a/kernel/sched/deadline.c >>>> +++ b/kernel/sched/deadline.c >>>> @@ -1090,7 +1090,8 @@ 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) >>>> + if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 && >>>> + is_leftmost(p, &rq->dl)) >>>> start_hrtick_dl(rq, p); >>>> } >>>> >>>> >>> -- >>> 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/ >> -- 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/