From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757460AbcAOMhF (ORCPT ); Fri, 15 Jan 2016 07:37:05 -0500 Received: from foss.arm.com ([217.140.101.70]:52501 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754824AbcAOMgo (ORCPT ); Fri, 15 Jan 2016 07:36:44 -0500 Date: Fri, 15 Jan 2016 12:37:08 +0000 From: Juri Lelli To: Viresh Kumar Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, peterz@infradead.org, rjw@rjwysocki.net, mturquette@baylibre.com, steve.muckle@linaro.org, vincent.guittot@linaro.org, morten.rasmussen@arm.com, dietmar.eggemann@arm.com Subject: Re: [RFC PATCH 13/19] cpufreq: fix locking of policy->rwsem in cpufreq_offline_prepare Message-ID: <20160115123708.GR18603@e106622-lin> References: <1452533760-13787-1-git-send-email-juri.lelli@arm.com> <1452533760-13787-14-git-send-email-juri.lelli@arm.com> <20160112105447.GE1084@ubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160112105447.GE1084@ubuntu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/01/16 16:24, Viresh Kumar wrote: > On 11-01-16, 17:35, Juri Lelli wrote: > > There are paths in cpufreq_offline_prepare where policy is used, but its > > rwsem is not held. > > > > Fix it. > > > > Cc: "Rafael J. Wysocki" > > Cc: Viresh Kumar > > Signed-off-by: Juri Lelli > > --- > > drivers/cpufreq/cpufreq.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > I know the locking in general in cpufreq core is poor. We recently > fixed lots of issues in governors .. > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > index 2c7cc6c73..91158b0 100644 > > --- a/drivers/cpufreq/cpufreq.c > > +++ b/drivers/cpufreq/cpufreq.c > > @@ -1332,13 +1332,13 @@ static void cpufreq_offline_prepare(unsigned int cpu) > > return; > > } > > > > + down_write(&policy->rwsem); > > if (has_target()) { > > int ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP); > > if (ret) > > pr_err("%s: Failed to stop governor\n", __func__); > > } > > > > - down_write(&policy->rwsem); > > cpumask_clear_cpu(cpu, policy->cpus); > > > > if (policy_is_inactive(policy)) { > > @@ -1356,12 +1356,16 @@ static void cpufreq_offline_prepare(unsigned int cpu) > > /* Start governor again for active policy */ > > if (!policy_is_inactive(policy)) { > > Why shouldn't this be under the lock? > > > if (has_target()) { > > - int ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); > > + int ret; > > + > > + down_write(&policy->rwsem); > > + ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); > > if (!ret) > > ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); > > > > if (ret) > > pr_err("%s: Failed to start governor\n", __func__); > > + up_write(&policy->rwsem); > > } > > } else if (cpufreq_driver->stop_cpu) { > > cpufreq_driver->stop_cpu(policy); > > And this ? > Right. Releasing rwsem at the end seems to work. Best, - Juri