Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754494AbaGHLue (ORCPT ); Tue, 8 Jul 2014 07:50:34 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:58549 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752768AbaGHLud (ORCPT ); Tue, 8 Jul 2014 07:50:33 -0400 Message-ID: <53BBDAFE.1070309@huawei.com> Date: Tue, 8 Jul 2014 19:50:22 +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> <53BBD4A7.5050701@huawei.com> In-Reply-To: <53BBD4A7.5050701@huawei.com> 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 19:23, xiaofeng.yan wrote: > 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. > I have tested this solution, It can work very well with deadline schedule class. kernel/sched/core.c | 9 ++++++++- kernel/sched/deadline.c | 5 +---- kernel/sched/fair.c | 8 -------- 3 files changed, 9 insertions(+), 13 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3bdf01b..cc9a058 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -442,8 +442,15 @@ 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. + */ + s64 delta = max_t(s64, delay, 10000LL); + time = ktime_add_ns(timer->base->get_time(), delta); hrtimer_set_expires(timer, time); if (rq == this_rq()) { diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fc4f98b1..9135771 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -997,10 +997,7 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, #ifdef CONFIG_SCHED_HRTICK 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 fea7d33..e5cfd57 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3857,14 +3857,6 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) resched_task(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); } } -- >> --- >> 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/ > > . > -- 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/