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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6A334C43381 for ; Wed, 17 Feb 2021 10:46:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FAE364E24 for ; Wed, 17 Feb 2021 10:46:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230071AbhBQKqy (ORCPT ); Wed, 17 Feb 2021 05:46:54 -0500 Received: from foss.arm.com ([217.140.110.172]:55806 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229707AbhBQKqo (ORCPT ); Wed, 17 Feb 2021 05:46:44 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 50CF31042; Wed, 17 Feb 2021 02:45:58 -0800 (PST) Received: from [10.57.61.90] (unknown [10.57.61.90]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 96EDF3F73B; Wed, 17 Feb 2021 02:45:55 -0800 (PST) Subject: Re: [PATCH] thermal: cpufreq_cooling: freq_qos_update_request() returns < 0 on error To: Viresh Kumar Cc: Amit Kucheria , Amit Daniel Kachhap , Daniel Lezcano , Javi Merino , Zhang Rui , "Peter Zijlstra (Intel)" , Ingo Molnar , Thara Gopinath , Vincent Guittot , "v5 . 7+" , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org References: <91749e19-9091-1292-b8aa-c923efa8021d@arm.com> <20210217103911.n34zzjttyso7dlco@vireshk-i7> From: Lukasz Luba Message-ID: <0b276055-e93a-3e08-5eee-662008d8db6c@arm.com> Date: Wed, 17 Feb 2021 10:45:53 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20210217103911.n34zzjttyso7dlco@vireshk-i7> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/17/21 10:39 AM, Viresh Kumar wrote: > On 17-02-21, 10:29, Lukasz Luba wrote: >> On 2/17/21 5:48 AM, Viresh Kumar wrote: >>> freq_qos_update_request() returns 1 if the effective constraint value >>> has changed, 0 if the effective constraint value has not changed, or a >>> negative error code on failures. >>> >>> The frequency constraints for CPUs can be set by different parts of the >>> kernel. If the maximum frequency constraint set by other parts of the >>> kernel are set at a lower value than the one corresponding to cooling >>> state 0, then we will never be able to cool down the system as >>> freq_qos_update_request() will keep on returning 0 and we will skip >>> updating cpufreq_state and thermal pressure. >> >> To be precised, thermal pressure signal is not so important in this >> mechanism and the 'cpufreq_state' has changed recently: > > Right, I wasn't concerned only about no thermal cooling, but both > thermal cooling and pressure. > >> 236761f19a4f373354 thermal/drivers/cpufreq_cooling: Update cpufreq_state >> only if state has changed > > This moved the assignment to a more logical place for me, i.e. not to > do that on errors, just that the block in which it landed may not get > called at all :( > >>> Fix that by doing the updates even in the case where >>> freq_qos_update_request() returns 0, as we have effectively set the >>> constraint to a new value even if the consolidated value of the >>> actual constraint is unchanged because of external factors. >>> >>> Cc: v5.7+ # v5.7+ >>> Reported-by: Thara Gopinath >>> Fixes: f12e4f66ab6a ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping") >> >> I'm not sure if that f12e4f is the root cause. > > Hmm, depends on how we define the problem :) > > If this was just about thermal-cooling not happening, then may be yes, > but to me it is rather about mishandled return value of > freq_qos_update_request() which has more than one side effects and so > I went for the main commit. > > This is also important as f12e4f66ab6a got merged in 5.7 and 236761f19 > merged in 5.11 and this patch needs to get applied in stable kernels > since 5.7 to fix it all. > 'to fix it all' - I agree