From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932881AbbAIMee (ORCPT ); Fri, 9 Jan 2015 07:34:34 -0500 Received: from terminus.zytor.com ([198.137.202.10]:60269 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932755AbbAIMe3 (ORCPT ); Fri, 9 Jan 2015 07:34:29 -0500 Date: Fri, 9 Jan 2015 04:33:43 -0800 From: tip-bot for Luca Abeni Message-ID: Cc: hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, tglx@linutronix.de, luca.abeni@unitn.it, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, raistlin@linux.it, stable@vger.kernel.org Reply-To: raistlin@linux.it, juri.lelli@gmail.com, stable@vger.kernel.org, luca.abeni@unitn.it, linux-kernel@vger.kernel.org, peterz@infradead.org, torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com, mingo@kernel.org In-Reply-To: <1418813432-20797-2-git-send-email-luca.abeni@unitn.it> References: <1418813432-20797-2-git-send-email-luca.abeni@unitn.it> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/deadline: Fix migration of SCHED_DEADLINE tasks Git-Commit-ID: 6a503c3be937d275113b702e0421e5b0720abe8a X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 6a503c3be937d275113b702e0421e5b0720abe8a Gitweb: http://git.kernel.org/tip/6a503c3be937d275113b702e0421e5b0720abe8a Author: Luca Abeni AuthorDate: Wed, 17 Dec 2014 11:50:31 +0100 Committer: Ingo Molnar CommitDate: Fri, 9 Jan 2015 11:18:56 +0100 sched/deadline: Fix migration of SCHED_DEADLINE tasks According to global EDF, tasks should be migrated between runqueues without checking if their scheduling deadlines and runtimes are valid. However, SCHED_DEADLINE currently performs such a check: a migration happens doing: deactivate_task(rq, next_task, 0); set_task_cpu(next_task, later_rq->cpu); activate_task(later_rq, next_task, 0); which ends up calling dequeue_task_dl(), setting the new CPU, and then calling enqueue_task_dl(). enqueue_task_dl() then calls enqueue_dl_entity(), which calls update_dl_entity(), which can modify scheduling deadline and runtime, breaking global EDF scheduling. As a result, some of the properties of global EDF are not respected: for example, a taskset {(30, 80), (40, 80), (120, 170)} scheduled on two cores can have unbounded response times for the third task even if 30/80+40/80+120/170 = 1.5809 < 2 This can be fixed by invoking update_dl_entity() only in case of wakeup, or if this is a new SCHED_DEADLINE task. Signed-off-by: Luca Abeni Signed-off-by: Peter Zijlstra (Intel) Acked-by: Juri Lelli Cc: Cc: Dario Faggioli Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1418813432-20797-2-git-send-email-luca.abeni@unitn.it Signed-off-by: Ingo Molnar --- kernel/sched/deadline.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index e5db8c6..55af498 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -826,10 +826,10 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, * parameters of the task might need updating. Otherwise, * we want a replenishment of its runtime. */ - if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH) - replenish_dl_entity(dl_se, pi_se); - else + if (dl_se->dl_new || flags & ENQUEUE_WAKEUP) update_dl_entity(dl_se, pi_se); + else if (flags & ENQUEUE_REPLENISH) + replenish_dl_entity(dl_se, pi_se); __enqueue_dl_entity(dl_se); }