Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756924AbaJXPMT (ORCPT ); Fri, 24 Oct 2014 11:12:19 -0400 Received: from relay.parallels.com ([195.214.232.42]:48443 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756856AbaJXPMQ (ORCPT ); Fri, 24 Oct 2014 11:12:16 -0400 Message-ID: <1414163521.19914.167.camel@tkhai> Subject: Re: [PATCH v4 1/6] sched/fair: Fix reschedule which is generated on throttled cfs_rq From: Kirill Tkhai To: Wanpeng Li CC: , , , , , , , , , Date: Fri, 24 Oct 2014 19:12:01 +0400 In-Reply-To: <544A1C96.10009@gmail.com> References: <20140806075138.24858.23816.stgit@tkhai> <1407312361.8424.35.camel@tkhai> <54498ED2.1070308@gmail.com> <1414130514.21462.2.camel@yandex.ru> <544A1C96.10009@gmail.com> Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org В Пт, 24/10/2014 в 17:32 +0800, Wanpeng Li пишет: > Hi Kirill, > 10/24/14, 2:01 PM, Kirill Tkhai: > > Hi, Wanpeng, > > > > the commit commentary confuses, I'm agree. Really it's just a cleanup. > > > > On Пт, 2014-10-24 at 07:27 +0800, Wanpeng Li wrote: > >> Hi Kirill, > >> 8/6/14, 4:06 PM, Kirill Tkhai: > >>> (sched_entity::on_rq == 1) does not guarantee the task is pickable; > >>> changes on throttled cfs_rq must not lead to reschedule. > >> Why (sched_entity::on_rq == 1) doesn't guarantee the task is pickable > >> since entity will be dequeued during throttling cfs_rq? > > Because one of task's (grand)parents in hierarhy may be throtthed and > > dequeued. > > > > But task_struct::on_rq check doesn't guarantee this too. So, just ignore > > commit commentary; the commentary is wrong. > > > >>> Check for task_struct::on_rq instead. > >> Do you mean task_struct::on_rq will be cleared during throttling cfs_rq? > >> I can't find codes do this. > > No, it not cleared. The commit commentary should be: > > "sched: Cleanup. Check task_struct::on_rq instead of sched_entity::on_rq, > > because it is the same for a task" > > IIUR, for fair class, sched_entity::on_rq will be set/clear during > enqueue/dequeue, task_struct::on_rq will changed during task migration, > I'm not sure why they are the same. prio_changed_fair() and switched_to_fair() can't be called during migration. They are called under pi_lock, and migration needs this lock too. > >>> Signed-off-by: Kirill Tkhai > >>> --- > >>> kernel/sched/fair.c | 6 +++--- > >>> 1 file changed, 3 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >>> index bfa3c86..6f0ce2b 100644 > >>> --- a/kernel/sched/fair.c > >>> +++ b/kernel/sched/fair.c > >>> @@ -7465,7 +7465,7 @@ static void task_fork_fair(struct task_struct *p) > >>> static void > >>> prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) > >>> { > >>> - if (!p->se.on_rq) > >>> + if (!p->on_rq) > >>> return; > >>> > >>> /* > >>> @@ -7521,15 +7521,15 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p) > >>> */ > >>> static void switched_to_fair(struct rq *rq, struct task_struct *p) > >>> { > >>> - struct sched_entity *se = &p->se; > >>> #ifdef CONFIG_FAIR_GROUP_SCHED > >>> + struct sched_entity *se = &p->se; > >>> /* > >>> * Since the real-depth could have been changed (only FAIR > >>> * class maintain depth value), reset depth properly. > >>> */ > >>> se->depth = se->parent ? se->parent->depth + 1 : 0; > >>> #endif > >>> - if (!se->on_rq) > >>> + if (!p->on_rq) > >>> return; > >>> > >>> /* > >>> > >>> > >>> > >>> -- > >>> 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/