From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753264Ab1ARTGl (ORCPT ); Tue, 18 Jan 2011 14:06:41 -0500 Received: from hera.kernel.org ([140.211.167.34]:53096 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752854Ab1ARTGi (ORCPT ); Tue, 18 Jan 2011 14:06:38 -0500 Date: Tue, 18 Jan 2011 19:06:14 GMT From: tip-bot for Mike Galbraith Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, efault@gmx.de, tglx@linutronix.de, venki@google.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, efault@gmx.de, tglx@linutronix.de, venki@google.com, mingo@elte.hu In-Reply-To: <1294202477.9384.5.camel@marge.simson.net> References: <1294202477.9384.5.camel@marge.simson.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched: Fix signed unsigned comparison in check_preempt_tick() Message-ID: Git-Commit-ID: d7d8294415f0ce4254827d4a2a5ee88b00be52a8 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]); Tue, 18 Jan 2011 19:06:14 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: d7d8294415f0ce4254827d4a2a5ee88b00be52a8 Gitweb: http://git.kernel.org/tip/d7d8294415f0ce4254827d4a2a5ee88b00be52a8 Author: Mike Galbraith AuthorDate: Wed, 5 Jan 2011 05:41:17 +0100 Committer: Ingo Molnar CommitDate: Tue, 18 Jan 2011 15:09:44 +0100 sched: Fix signed unsigned comparison in check_preempt_tick() Signed unsigned comparison may lead to superfluous resched if leftmost is right of the current task, wasting a few cycles, and inadvertently _lengthening_ the current task's slice. Reported-by: Venkatesh Pallipadi Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra LKML-Reference: <1294202477.9384.5.camel@marge.simson.net> Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 414145c..77e9166 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1062,6 +1062,9 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) struct sched_entity *se = __pick_next_entity(cfs_rq); s64 delta = curr->vruntime - se->vruntime; + if (delta < 0) + return; + if (delta > ideal_runtime) resched_task(rq_of(cfs_rq)->curr); }