Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753277AbbG0MjR (ORCPT ); Mon, 27 Jul 2015 08:39:17 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:36661 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751857AbbG0MjP (ORCPT ); Mon, 27 Jul 2015 08:39:15 -0400 MIME-Version: 1.0 In-Reply-To: <20150727022952.GF19944@linux> References: <1660815.CyKx9SEI9c@vostro.rjw.lan> <20150725130002.GC1691@linux> <2161701.diIE0m8ocR@vostro.rjw.lan> <20150727022952.GF19944@linux> Date: Mon, 27 Jul 2015 14:39:14 +0200 X-Google-Sender-Auth: zDjooGRZTmhePU3gj_Mz7FeoKGM Message-ID: Subject: Re: [PATCH v3] cpufreq: Avoid attempts to create duplicate symbolic links From: "Rafael J. Wysocki" To: Viresh Kumar , Russell King Cc: "Rafael J. Wysocki" , Linux PM list , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3145 Lines: 68 On Mon, Jul 27, 2015 at 4:29 AM, Viresh Kumar wrote: > On 26-07-15, 02:28, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki >> >> After commit 87549141d516 (cpufreq: Stop migrating sysfs files on >> hotplug) there is a problem with CPUs that share cpufreq policy >> objects with other CPUs and are initially offline. >> >> Say CPU1 shares a policy with CPU0 which is online and is registered >> first. As part of the registration process, cpufreq_add_dev() is >> called for it. It creates the policy object and a symbolic link >> to it from the CPU1's sysfs directory. If CPU1 is registered >> subsequently and it is offline at that time, cpufreq_add_dev() will >> attempt to create a symbolic link to the policy object for it, but >> that link is present already, so a warning about that will be >> triggered. >> >> To avoid that warning, make cpufreq use an additional CPU mask >> containing related CPUs that are actually present for each policy >> object. That mask is initialized when the policy object is populated >> after its creation (for the first online CPU using it) and it includes >> CPUs from the "policy CPUs" mask returned by the cpufreq driver's >> ->init() callback that are physically present at that time. Symbolic >> links to the policy are created only for the CPUs in that mask. >> >> If cpufreq_add_dev() is invoked for an offline CPU, it checks the >> new mask and only creates the symlink if the CPU was not in it (the >> CPU is added to the mask at the same time). >> >> In turn, cpufreq_remove_dev() drops the given CPU from the new mask, >> removes its symlink to the policy object and returns, unless it is >> the CPU owning the policy object. In that case, the policy object >> is moved to a new CPU's sysfs directory or deleted if the CPU being >> removed was the last user of the policy. >> >> While at it, notice that cpufreq_remove_dev() can't fail, because >> its return value is ignored, so make it ignore return values from >> __cpufreq_remove_dev_prepare() and __cpufreq_remove_dev_finish() >> and prevent these functions from aborting on errors returned by >> __cpufreq_governor(). Also drop the now unused sif argument from >> them. >> >> Fixes: 87549141d516 (cpufreq: Stop migrating sysfs files on hotplug) >> Signed-off-by: Rafael J. Wysocki >> Reported-by: Russell King >> --- >> >> This goes back to the https://patchwork.kernel.org/patch/6856011/ >> idea, but has a couple of bugs fixed and goes a it further with >> cleaning things up. >> >> --- >> drivers/cpufreq/cpufreq.c | 108 +++++++++++++++++++++++----------------------- >> include/linux/cpufreq.h | 1 >> 2 files changed, 56 insertions(+), 53 deletions(-) > > Acked-by: Viresh Kumar Thanks! Russell, can you test this one, please? Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/