From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752087AbeCXMrV (ORCPT ); Sat, 24 Mar 2018 08:47:21 -0400 Received: from mail-wr0-f178.google.com ([209.85.128.178]:36373 "EHLO mail-wr0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751898AbeCXMrU (ORCPT ); Sat, 24 Mar 2018 08:47:20 -0400 X-Google-Smtp-Source: AG47ELvyOTdpgi82St0+UF0jJny2CUl6ca2Ba+MkssHYubJ+fTBKOKjFYQdEFmZdjV+z/z0Gp89DKg== Subject: Re: Problem with commit 31e77c93e432 "sched/fair: Update blocked load when newly idle" To: Vincent Guittot Cc: "Peter Zijlstra (Intel)" , Ingo Molnar , Linux Kernel Mailing List References: <20180324064627.GA10884@linaro.org> From: Heiner Kallweit Message-ID: Date: Sat, 24 Mar 2018 13:47:13 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180324064627.GA10884@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 24.03.2018 um 07:46 schrieb Vincent Guittot: > 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 ? > Thanks for the quick feedback. The change however didn't fix the probem, I didn't notice any changed behavior. > --- > 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. >