From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752638AbdHJMKn (ORCPT ); Thu, 10 Aug 2017 08:10:43 -0400 Received: from terminus.zytor.com ([65.50.211.136]:52945 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751709AbdHJMKl (ORCPT ); Thu, 10 Aug 2017 08:10:41 -0400 Date: Thu, 10 Aug 2017 05:07:08 -0700 From: tip-bot for Vincent Guittot Message-ID: Cc: peterz@infradead.org, tglx@linutronix.de, mingo@kernel.org, torvalds@linux-foundation.org, hpa@zytor.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org Reply-To: peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, vincent.guittot@linaro.org, hpa@zytor.com, torvalds@linux-foundation.org In-Reply-To: <1498885573-18984-1-git-send-email-vincent.guittot@linaro.org> References: <1498885573-18984-1-git-send-email-vincent.guittot@linaro.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/pelt: Fix false running accounting Git-Commit-ID: f235a54f00449c611f85173fe8a66c4d189c5ce1 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: f235a54f00449c611f85173fe8a66c4d189c5ce1 Gitweb: http://git.kernel.org/tip/f235a54f00449c611f85173fe8a66c4d189c5ce1 Author: Vincent Guittot AuthorDate: Sat, 1 Jul 2017 07:06:13 +0200 Committer: Ingo Molnar CommitDate: Thu, 10 Aug 2017 12:18:15 +0200 sched/pelt: Fix false running accounting The running state is a subset of runnable state which means that running can't be set if runnable (weight) is cleared. There are corner cases where the current sched_entity has been already dequeued but cfs_rq->curr has not been updated yet and still points to the dequeued sched_entity. If ___update_load_avg() is called at that time, weight will be 0 and running will be set which is not possible. This case happens during pick_next_task_fair() when a cfs_rq becomes idles. The current sched_entity has been dequeued so se->on_rq is cleared and cfs_rq->weight is null. But cfs_rq->curr still points to se (it will be cleared when picking the idle thread). Because the cfs_rq becomes idle, idle_balance() is called and ends up to call update_blocked_averages() with these wrong running and runnable states. Add a test in ___update_load_avg() to correct the running state in this case. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Morten.Rasmussen@arm.com Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dietmar.eggemann@arm.com Link: http://lkml.kernel.org/r/1498885573-18984-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 75c58c7..ef5b66b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2991,6 +2991,18 @@ ___update_load_avg(u64 now, int cpu, struct sched_avg *sa, sa->last_update_time += delta << 10; /* + * running is a subset of runnable (weight) so running can't be set if + * runnable is clear. But there are some corner cases where the current + * se has been already dequeued but cfs_rq->curr still points to it. + * This means that weight will be 0 but not running for a sched_entity + * but also for a cfs_rq if the latter becomes idle. As an example, + * this happens during idle_balance() which calls + * update_blocked_averages() + */ + if (!weight) + running = 0; + + /* * Now we know we crossed measurement unit boundaries. The *_avg * accrues by two steps: *