From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AEBA8C4321D for ; Thu, 16 Aug 2018 14:21:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7152C2147D for ; Thu, 16 Aug 2018 14:21:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7152C2147D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391778AbeHPRUR (ORCPT ); Thu, 16 Aug 2018 13:20:17 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:37254 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391764AbeHPRUQ (ORCPT ); Thu, 16 Aug 2018 13:20:16 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F373F80D; Thu, 16 Aug 2018 07:21:21 -0700 (PDT) Received: from queper01-lin (queper01-lin.Emea.Arm.com [10.4.13.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 30CC73F5D0; Thu, 16 Aug 2018 07:21:19 -0700 (PDT) Date: Thu, 16 Aug 2018 15:21:17 +0100 From: Quentin Perret To: Dietmar Eggemann Cc: Patrick Bellasi , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting Message-ID: <20180816142115.v7nybc4qfazdiz6n@queper01-lin> References: <20180806163946.28380-1-patrick.bellasi@arm.com> <20180806163946.28380-4-patrick.bellasi@arm.com> <20180814164905.GG2605@e110439-lin> <7c45c1a8-24cb-6798-5b6f-3b5dfc9b490d@arm.com> <20180815105428.GA7388@e110439-lin> <20180816133249.GA2964@e110439-lin> <20180816133737.xfwfoenbhb5wnndi@queper01-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 16 Aug 2018 at 15:45:45 (+0200), Dietmar Eggemann wrote: > On 08/16/2018 03:37 PM, Quentin Perret wrote: > > > > IMHO, if this is something which should not happen at all, a BUG_ON() is the > > > > right thing to do here. > > > > > > I don't agree on that. I agree it should not happen but since it's a > > > recoverable error it think we should not panic. > > > > FWIW, if this is a recoverable error, I think Linus will agree with > > Patrick on this one :-) > > > > https://lkml.org/lkml/2016/10/4/1 > > Yeah, not really agreeing here that this is a recoverable error. A non-recoverable scenario could be, for example, if you corrupt your stack and there is absolutely _nothing_ you can do to keep the system up and running, because it's just too broken. I don't feel like we're talking about such an extreme case here ... > Besides, we > only consider under-run here, what about over-run? > > Currently this warning doesn't hit and if the code will be changed and it > hits, I still find a BUG_ON more appealing here ... > > So this error scenario can happen over and over again and we always recover > from ? The important thing is that we find the culprit for this behaviour as > fast as possible ... Agreed, we want to debug that ASAP, but WARN should let us do that just fine, I think. Quentin