Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755728AbaF3L6U (ORCPT ); Mon, 30 Jun 2014 07:58:20 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:52085 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754003AbaF3Lx0 (ORCPT ); Mon, 30 Jun 2014 07:53:26 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Linus Torvalds , Ingo Molnar , Jiri Slaby Subject: [PATCH 3.12 013/181] sched: Make scale_rt_power() deal with backward clocks Date: Mon, 30 Jun 2014 13:50:34 +0200 Message-Id: <5ff029e2b396ac09fc52addd73bb0f4003c70ef2.1404128997.git.jslaby@suse.cz> X-Mailer: git-send-email 2.0.0 In-Reply-To: <61844d8e25eb8899b0836afa9796fa239db80f1f.1404128997.git.jslaby@suse.cz> References: <61844d8e25eb8899b0836afa9796fa239db80f1f.1404128997.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit cadefd3d6cc914d95163ba1eda766bfe7ce1e5b7 upstream. 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 Signed-off-by: Jiri Slaby --- 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 25658d2c68d0..898622244bdf 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4404,6 +4404,7 @@ 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 @@ -4412,7 +4413,11 @@ 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 */ -- 2.0.0 -- 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/