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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 0A89EC432C0 for ; Wed, 27 Nov 2019 12:08:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC03D2075C for ; Wed, 27 Nov 2019 12:08:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726873AbfK0MIV (ORCPT ); Wed, 27 Nov 2019 07:08:21 -0500 Received: from foss.arm.com ([217.140.110.172]:46892 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726852AbfK0MIV (ORCPT ); Wed, 27 Nov 2019 07:08:21 -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 2325530E; Wed, 27 Nov 2019 04:08:20 -0800 (PST) Received: from bogus (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A73C73F6C4; Wed, 27 Nov 2019 04:08:18 -0800 (PST) Date: Wed, 27 Nov 2019 12:08:16 +0000 From: Sudeep Holla To: Dietmar Eggemann Cc: Viresh Kumar , "Rafael J . Wysocki" , Liviu Dudau , Lorenzo Pieralisi , Morten Rasmussen , Sudeep Holla , Lukasz Luba , linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cpufreq: vexpress-spc: Fix wrong alternation of policy->related_cpus during CPU hp Message-ID: <20191127120816.GC29301@bogus> References: <20191127114801.23837-1-dietmar.eggemann@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191127114801.23837-1-dietmar.eggemann@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Wed, Nov 27, 2019 at 12:48:01PM +0100, Dietmar Eggemann wrote: > Since commit ca74b316df96 ("arm: Use common cpu_topology structure and > functions.") the core cpumask has to be modified during cpu hotplug > operations. > > ("arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC") > [1] fixed that but revealed another issue on TC2, i.e in its cpufreq > driver. > > During CPU hp stress operations on multiple CPUs, policy->related_cpus > can be altered. This is wrong since this cpumask should contain the > online and offline CPUs. > > The WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus)) in > cpufreq_online() triggers in this case. > > The core cpumask can't be used to set the policy->cpus in > ve_spc_cpufreq_init() anymore in case it is called via > cpuhp_cpufreq_online()->cpufreq_online()->cpufreq_driver->init(). > > An empty online() callback can be used to avoid that the init() > driver function is called during CPU hotplug in so that > policy->related_cpus will not be changed. > Unlike DT based drivers, it not easy to get the fixed cpumask unless we add some mechanism to extract it based on clks/OPP added. I prefer this simple solution instead. > Implementing an online() also requires an offline() callback. > > Tested on TC2 with CPU hp stress test (CPU hp from multiple CPUs at > the same time). > > [1] > https://lore.kernel.org/r/20191127103353.12417-1-dietmar.eggemann@arm.com > Reviewed-by: Sudeep Holla Tested-by: Sudeep Holla -- Regards, Sudeep