Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753943AbaDRNHS (ORCPT ); Fri, 18 Apr 2014 09:07:18 -0400 Received: from terminus.zytor.com ([198.137.202.10]:38753 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753760AbaDRNHJ (ORCPT ); Fri, 18 Apr 2014 09:07:09 -0400 Date: Fri, 18 Apr 2014 06:06:08 -0700 From: tip-bot for Peter Zijlstra Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, bitbucket@online.de, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, bitbucket@online.de, tglx@linutronix.de In-Reply-To: <20140227094035.GZ9987@twins.programming.kicks-ass.net> References: <20140227094035.GZ9987@twins.programming.kicks-ass.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: Make scale_rt_power() deal with backward clocks Git-Commit-ID: cadefd3d6cc914d95163ba1eda766bfe7ce1e5b7 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: cadefd3d6cc914d95163ba1eda766bfe7ce1e5b7 Gitweb: http://git.kernel.org/tip/cadefd3d6cc914d95163ba1eda766bfe7ce1e5b7 Author: Peter Zijlstra AuthorDate: Thu, 27 Feb 2014 10:40:35 +0100 Committer: Ingo Molnar CommitDate: Fri, 18 Apr 2014 12:07:21 +0200 sched: Make scale_rt_power() deal with backward clocks Mike reported that, while unlikely, its entirely possible for scale_rt_power() to see the time go backwards. This yields rather 'interesting' results. So like all other sites that deal with clocks; make this one ignore backward clock movement too. Reported-by: Mike Galbraith Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20140227094035.GZ9987@twins.programming.kicks-ass.net Cc: Linus Torvalds Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7570dd9..5e157f1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5564,6 +5564,7 @@ static unsigned long scale_rt_power(int cpu) { struct rq *rq = cpu_rq(cpu); u64 total, available, age_stamp, avg; + s64 delta; /* * Since we're reading these variables without serialization make sure @@ -5572,7 +5573,11 @@ static unsigned long scale_rt_power(int cpu) age_stamp = ACCESS_ONCE(rq->age_stamp); avg = ACCESS_ONCE(rq->rt_avg); - total = sched_avg_period() + (rq_clock(rq) - age_stamp); + delta = rq_clock(rq) - age_stamp; + if (unlikely(delta < 0)) + delta = 0; + + total = sched_avg_period() + delta; if (unlikely(total < avg)) { /* Ensures that power won't end up being negative */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/