linux-kernel - Re: [RFC PATCH 08/19] cpufreq: fix warning for cpufreq_init_policy unlocked access to cpufreq_governor

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Message-ID: <20160112155200.GC18734@e106622-lin>
Date:	Tue, 12 Jan 2016 15:52:00 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	peterz@...radead.org, rjw@...ysocki.net, mturquette@...libre.com,
	steve.muckle@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com
Subject: Re: [RFC PATCH 08/19] cpufreq: fix warning for cpufreq_init_policy
 unlocked access to cpufreq_governor_list

On 12/01/16 15:39, Viresh Kumar wrote:
> On 11-01-16, 17:35, Juri Lelli wrote:
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 7dae7f3..d065435 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -969,6 +969,7 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
> >  
> >  	memcpy(&new_policy, policy, sizeof(*policy));
> >  
> > +	mutex_lock(&cpufreq_governor_mutex);
> >  	/* Update governor of new_policy to the governor used before hotplug */
> >  	gov = find_governor(policy->last_governor);
> 
> You should take the lock within find_governor() instead, i.e.  around
> the while loop.
> 

Other users (i.e., cpufreq_parse_governor and cpufreq_register_governor)
needs to take the mutex externally. So, we need to unify this behaviour.

Best,

- Juri

> >  	if (gov)
> > @@ -976,6 +977,7 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
> >  				policy->governor->name, policy->cpu);
> >  	else
> >  		gov = CPUFREQ_DEFAULT_GOVERNOR;
> > +	mutex_unlock(&cpufreq_governor_mutex);
> >  
> >  	new_policy.governor = gov;
> >  
> > -- 
> > 2.2.2
> 
> -- 
> viresh
>