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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 646FCC4321D for ; Thu, 16 Aug 2018 13:45:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 120C421480 for ; Thu, 16 Aug 2018 13:45:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 120C421480 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 S2388335AbeHPQoe (ORCPT ); Thu, 16 Aug 2018 12:44:34 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:36940 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729292AbeHPQoe (ORCPT ); Thu, 16 Aug 2018 12:44:34 -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 6775780D; Thu, 16 Aug 2018 06:45:51 -0700 (PDT) Received: from [192.168.0.102] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 405EB3F5BC; Thu, 16 Aug 2018 06:45:48 -0700 (PDT) Subject: Re: [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting To: Quentin Perret , Patrick Bellasi Cc: 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 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> From: Dietmar Eggemann Message-ID: Date: Thu, 16 Aug 2018 15:45:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180816133737.xfwfoenbhb5wnndi@queper01-lin> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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 ... Warning or bug, at least a stack trace is necessary.