From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751127AbdE3L3r (ORCPT ); Tue, 30 May 2017 07:29:47 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:46316 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750902AbdE3L3q (ORCPT ); Tue, 30 May 2017 07:29:46 -0400 Date: Tue, 30 May 2017 13:29:32 +0200 From: Peter Zijlstra To: Daniel Bristot de Oliveira Cc: linux-kernel@vger.kernel.org, Xunlei Pang , Ingo Molnar , Juri Lelli , Steven Rostedt , Luca Abeni , Tommaso Cucinotta , Romulo Silva de Oliveira Subject: Re: [PATCH V2 2/2] sched/deadline: Use the revised wakeup rule for suspending constrained dl tasks Message-ID: <20170530112932.yjw2dobbvhpyd2mp@hirez.programming.kicks-ass.net> References: <5c800ab3a74a168a84ee5f3f84d12a02e11383be.1495803804.git.bristot@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5c800ab3a74a168a84ee5f3f84d12a02e11383be.1495803804.git.bristot@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 29, 2017 at 04:24:03PM +0200, Daniel Bristot de Oliveira wrote: > +/* > + * Regarding the deadline, a task with implicit deadline has a relative > + * deadline == relative period. A task with constrained deadline has a > + * relative deadline <= relative period. > + * > + * Linux supports constrained deadline tasks. However, there are some > + * restrictions applied only for tasks with constrained deadline which are > + * not implicit deadline tasks. See update_dl_entity() to know more about > + * such restrictions. > + * > + * The dl_is_constrained() returns true if the task has a constrained but > + * not implicit deadline. > + */ > +static inline bool dl_is_constrained(struct sched_dl_entity *dl_se) > +{ > + return dl_se->dl_deadline < dl_se->dl_period; > +} OK, given that: implicit - deadline == period constrained - deadline <= period and thus constrained can still be implicit, our function dl_is_constrained() is wrong. I've replaced the above with dl_is_implicit(). --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -740,19 +740,17 @@ update_dl_revised_wakeup(struct sched_dl /* * Regarding the deadline, a task with implicit deadline has a relative * deadline == relative period. A task with constrained deadline has a - * relative deadline < relative period. + * relative deadline <= relative period. * - * We supports constrained deadline tasks. However, there are some - * restrictions applied only for tasks with constrained deadline which are - * not implicit deadline tasks. See update_dl_entity() to know more about - * such restrictions. + * We support constrained deadline tasks. However, there are some restrictions + * applied only for tasks which do not have an implicit deadline. See + * update_dl_entity() to know more about such restrictions. * - * The dl_is_constrained() returns true if the task has a constrained - * (not implicit) deadline. + * The dl_is_implicit() returns true if the task has an implicit deadline. */ -static inline bool dl_is_constrained(struct sched_dl_entity *dl_se) +static inline bool dl_is_implicit(struct sched_dl_entity *dl_se) { - return dl_se->dl_deadline < dl_se->dl_period; + return dl_se->dl_deadline == dl_se->dl_period; } /* @@ -794,7 +792,7 @@ static void update_dl_entity(struct sche if (dl_time_before(dl_se->deadline, rq_clock(rq)) || dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) { - if (unlikely(dl_is_constrained(dl_se) && + if (unlikely(!dl_is_implicit(dl_se) && !dl_time_before(dl_se->deadline, rq_clock(rq)) && !dl_se->dl_boosted)){ update_dl_revised_wakeup(dl_se, rq); @@ -1386,7 +1384,7 @@ static void enqueue_task_dl(struct rq *r * If that is the case, the task will be throttled and * the replenishment timer will be set to the next period. */ - if (!p->dl.dl_throttled && dl_is_constrained(&p->dl)) + if (!p->dl.dl_throttled && !dl_is_implicit(&p->dl)) dl_check_constrained_dl(&p->dl); if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE) {