Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754108AbaGHLX3 (ORCPT ); Tue, 8 Jul 2014 07:23:29 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:13508 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752768AbaGHLX2 (ORCPT ); Tue, 8 Jul 2014 07:23:28 -0400 Message-ID: <53BBD4A7.5050701@huawei.com> Date: Tue, 8 Jul 2014 19:23:19 +0800 From: "xiaofeng.yan" User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Peter Zijlstra CC: , , , Subject: Re: [PATCH] sched/deadline: overrun could happen in start_hrtick_dl References: <1404809607-26197-1-git-send-email-xiaofeng.yan@huawei.com> <20140708093334.GD6758@twins.programming.kicks-ass.net> In-Reply-To: <20140708093334.GD6758@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.111.68.133] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/7/8 17:33, Peter Zijlstra wrote: > On Tue, Jul 08, 2014 at 08:53:27AM +0000, xiaofeng.yan wrote: >> static void start_hrtick_dl(struct rq *rq, struct task_struct *p) >> { >> - s64 delta = p->dl.dl_runtime - p->dl.runtime; >> - >> - if (delta > 10000) >> - hrtick_start(rq, p->dl.runtime); >> + delta = max_t(s64, 10000LL, delta); >> + hrtick_start(rq, delta); >> } > no, no, no. I said to unify the test. I understand your idea after reading the next patch. This is good solution. I will test it with your patch. > --- > kernel/sched/core.c | 9 ++++++++- > kernel/sched/deadline.c | 3 +-- > kernel/sched/fair.c | 7 ------- > 3 files changed, 9 insertions(+), 10 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index e1a2f31bb0cb..c7b8a6fbac66 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -444,7 +444,14 @@ static void __hrtick_start(void *arg) > void hrtick_start(struct rq *rq, u64 delay) > { > struct hrtimer *timer = &rq->hrtick_timer; > - ktime_t time = ktime_add_ns(timer->base->get_time(), delay); > + ktime_t time; > + > + /* > + * Don't schedule slices shorter than 10000ns, that just > + * doesn't make sense and can cause timer DoS. > + */ > + delta = max_t(s64, delta, 10000LL); transfer the argument delta to delay > + time = ktime_add_ns(timer->base->get_time(), delay); > > hrtimer_set_expires(timer, time); > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index fc4f98b1258f..e1e24eea8061 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -999,8 +999,7 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p) > { > s64 delta = p->dl.dl_runtime - p->dl.runtime; > > - if (delta > 10000) > - hrtick_start(rq, p->dl.runtime); > + hrtick_start(rq, p->dl.runtime); > } > #endif > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 923fe32db6b3..713c58d2a7b0 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3901,13 +3901,6 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) > return; > } > > - /* > - * Don't schedule slices shorter than 10000ns, that just > - * doesn't make sense. Rely on vruntime for fairness. > - */ > - if (rq->curr != p) > - delta = max_t(s64, 10000LL, delta); > - > hrtick_start(rq, delta); > } > } -- 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/