From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932950AbbA0Mpw (ORCPT ); Tue, 27 Jan 2015 07:45:52 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:34961 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758382AbbA0MRk (ORCPT ); Tue, 27 Jan 2015 07:17:40 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Luca Abeni , "Peter Zijlstra (Intel)" , Dario Faggioli , Linus Torvalds , Ingo Molnar , Luis Henriques Subject: [PATCH 3.16.y-ckt 028/126] sched/deadline: Fix migration of SCHED_DEADLINE tasks Date: Tue, 27 Jan 2015 12:15:33 +0000 Message-Id: <1422361031-19364-29-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1422361031-19364-1-git-send-email-luis.henriques@canonical.com> References: <1422361031-19364-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt5 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Luca Abeni commit 6a503c3be937d275113b702e0421e5b0720abe8a upstream. 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: 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 Signed-off-by: Luis Henriques --- 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 fc4f98b1258f..a07b08ce8307 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -823,10 +823,10 @@ 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); } -- 2.1.4