From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753061Ab1GUS2O (ORCPT ); Thu, 21 Jul 2011 14:28:14 -0400 Received: from hera.kernel.org ([140.211.167.34]:49825 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751419Ab1GUS2K (ORCPT ); Thu, 21 Jul 2011 14:28:10 -0400 Date: Thu, 21 Jul 2011 18:27:57 GMT From: tip-bot for Paul Turner Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, pjt@google.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, pjt@google.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: update correct entity's runtime in check_preempt_wakeup() Git-Commit-ID: 9bbd7374361d9bfc75108c3ad1c1b6db28b1be59 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 21 Jul 2011 18:27:58 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 9bbd7374361d9bfc75108c3ad1c1b6db28b1be59 Gitweb: http://git.kernel.org/tip/9bbd7374361d9bfc75108c3ad1c1b6db28b1be59 Author: Paul Turner AuthorDate: Tue, 5 Jul 2011 19:07:21 -0700 Committer: Ingo Molnar CommitDate: Thu, 21 Jul 2011 18:01:43 +0200 sched: update correct entity's runtime in check_preempt_wakeup() While looking at check_preempt_wakeup() I realized that we are potentially updating the wrong entity in the fair-group scheduling case. In this case the current task's cfs_rq may not be the same as the one used for the comparison between the waking task and the existing task's vruntime. This potentially results in us using a stale vruntime in the pre-emption decision, providing a small false preference for the previous task. The effects of this are bounded since we always perform a hierarchal update on the tick. Signed-off-by: Paul Turner Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/CAPM31R+2Ke2urUZKao5W92_LupdR4AYEv-EZWiJ3tG=tEes2cw@mail.gmail.com Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index e7d67a9..f88720b 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1919,8 +1919,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ if (!sched_feat(WAKEUP_PREEMPT)) return; - update_curr(cfs_rq); find_matching_se(&se, &pse); + update_curr(cfs_rq_of(se)); BUG_ON(!pse); if (wakeup_preempt_entity(se, pse) == 1) { /*