From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751009AbeCXGqd (ORCPT ); Sat, 24 Mar 2018 02:46:33 -0400 Received: from mail-wr0-f182.google.com ([209.85.128.182]:37141 "EHLO mail-wr0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763AbeCXGqb (ORCPT ); Sat, 24 Mar 2018 02:46:31 -0400 X-Google-Smtp-Source: AG47ELuyWG5WT4+YpyS1pAsiE4FlyLQWips+Mp01GAQFnIQMroy8lQUtiRb9Cw5JTi1I/ZvjNCOSlQ== Date: Sat, 24 Mar 2018 07:46:27 +0100 From: Vincent Guittot To: Heiner Kallweit Cc: "Peter Zijlstra (Intel)" , Ingo Molnar , Linux Kernel Mailing List Subject: Re: Problem with commit 31e77c93e432 "sched/fair: Update blocked load when newly idle" Message-ID: <20180324064627.GA10884@linaro.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Heiner, Le Friday 23 Mar 2018 à 22:28:09 (+0100), Heiner Kallweit a écrit : > Recently I started to get the following problems with linux-next: > > - When working via Putty/SSH on the system the console frequently freezes > for few seconds. Sometimes only opening a second console makes the > first one react again. > > - I get "INFO: rcu_sched detected stalls on CPUs/tasks:" warnings as > described in [1]. > > Bisecting the issue resulted in: > > 31e77c93e432dec79c7d90b888bbfc3652592741 is the first bad commit > commit 31e77c93e432dec79c7d90b888bbfc3652592741 > Author: Vincent Guittot > Date: Wed Feb 14 16:26:46 2018 +0100 > > sched/fair: Update blocked load when newly idle > > When NEWLY_IDLE load balance is not triggered, we might need to update the > blocked load anyway. We can kick an ilb so an idle CPU will take care of > updating blocked load or we can try to update them locally before entering > idle. In the latter case, we reuse part of the nohz_idle_balance. > > After reversing this commit at least the issue with the freezing console > is gone. The second one appeared only sporadically, I still have to see > whether it pops up again. > Can you check if the change below fix the problem ? --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3582117..672f212 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9430,6 +9430,9 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags, has_blocked_load |= update_nohz_stats(rq, true); + if (flags == NOHZ_STATS_KICK) + continue; + /* * If time for next balance is due, * do the balance. -- > System is a Zotac CI321 mini PC with Intel Celeron 2961Y CPU. > If you need more details, please let me know. > > Regards, Heiner > > [1] https://lkml.org/lkml/2018/3/22/605