From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756933AbaJHMcX (ORCPT ); Wed, 8 Oct 2014 08:32:23 -0400 Received: from mail-pd0-f174.google.com ([209.85.192.174]:54159 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756490AbaJHMcT (ORCPT ); Wed, 8 Oct 2014 08:32:19 -0400 Message-ID: <54352ECB.5030507@gmail.com> Date: Wed, 08 Oct 2014 20:32:11 +0800 From: Wanpeng Li User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Juri Lelli , peterz@infradead.org CC: mingo@redhat.com, juri.lelli@gmail.com, raistlin@linux.it, michael@amarulasolutions.com, fchecconi@gmail.com, daniel.wagner@bmw-carit.de, vincent@legout.info, luca.abeni@unitn.it, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling to different class References: <1411118561-26323-1-git-send-email-juri.lelli@arm.com> <1411118561-26323-2-git-send-email-juri.lelli@arm.com> In-Reply-To: <1411118561-26323-2-git-send-email-juri.lelli@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Juri, 于 9/19/14, 5:22 PM, Juri Lelli 写道: > When a task is using SCHED_DEADLINE and the user setschedules it to a different > class its sched_dl_entity static parameters are not cleaned up. This causes a > bug if the user sets it back to SCHED_DEADLINE with the same parameters again. > The problem resides in the check we perform at the very beginning of > dl_overflow(): > > if (new_bw == p->dl.dl_bw) > return 0; > > This condition is met in the case depicted above, so the function returns and > dl_b->total_bw is not updated (the p->dl.dl_bw is not added to it). After this, As you know there is no static parameter clear before this patch, so if p->dl.dl_bw will decrease from dl_b->total_bw when the user setschedules to a different class instead of dl? Regards, Wanpeng Li > admission control is broken. > > This patch fixes the thing, properly clearing static parameters for a task > that ceases to use SCHED_DEADLINE. > > Reported-by: Daniele Alessandrelli > Reported-by: Daniel Wagner > Reported-by: Vincent Legout > Tested-by: Luca Abeni > Signed-off-by: Juri Lelli > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Juri Lelli > Cc: Dario Faggioli > Cc: Michael Trimarchi > Cc: Fabio Checconi > Cc: linux-kernel@vger.kernel.org > --- > kernel/sched/core.c | 19 +++++++++++++++---- > kernel/sched/deadline.c | 2 ++ > kernel/sched/sched.h | 3 +++ > 3 files changed, 20 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index ec1a286..581a429 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1776,6 +1776,20 @@ int wake_up_state(struct task_struct *p, unsigned int state) > } > > /* > + * This function clears the sched_dl_entity static params. > + */ > +void __dl_clear_params(struct task_struct *p) > +{ > + struct sched_dl_entity *dl_se = &p->dl; > + > + dl_se->dl_runtime = 0; > + dl_se->dl_deadline = 0; > + dl_se->dl_period = 0; > + dl_se->flags = 0; > + dl_se->dl_bw = 0; > +} > + > +/* > * Perform scheduler related setup for a newly forked process p. > * p is forked by current. > * > @@ -1799,10 +1813,7 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) > > RB_CLEAR_NODE(&p->dl.rb_node); > hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > - p->dl.dl_runtime = p->dl.runtime = 0; > - p->dl.dl_deadline = p->dl.deadline = 0; > - p->dl.dl_period = 0; > - p->dl.flags = 0; > + __dl_clear_params(p); > > INIT_LIST_HEAD(&p->rt.run_list); > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 255ce13..4a51b14 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -1569,6 +1569,8 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p) > if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy)) > hrtimer_try_to_cancel(&p->dl.dl_timer); > > + __dl_clear_params(p); > + > #ifdef CONFIG_SMP > /* > * Since this might be the only -deadline task on the rq, > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 579712f..4890484 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -126,6 +126,9 @@ struct rt_bandwidth { > u64 rt_runtime; > struct hrtimer rt_period_timer; > }; > + > +void __dl_clear_params(struct task_struct *p); > + > /* > * To keep the bandwidth of -deadline tasks and groups under control > * we need some place where: