linux-kernel - RE: [PATCH v2 linux-next 2/2] cpufreq: Convert the cpufreq_driver

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Message-ID: <74F10842A85F514CA8D8C487E74474BB2D30DF27@P-EXMB1-DC21.corp.sgi.com>
Date:	Tue, 12 Feb 2013 04:03:42 +0000
From:	Nathan Zimmer <nzimmer@....com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>
Subject: RE: [PATCH v2 linux-next 2/2] cpufreq: Convert the
 cpufreq_driver_lock to use the rcu

Argh, your right.  I completely misread that section.
It'll take me a few days to respin and retest properly.

Thanks, 
Nate

________________________________________
From: Rafael J. Wysocki [rjw@...k.pl]
Sent: Monday, February 11, 2013 1:36 PM
To: Nathan Zimmer
Cc: viresh.kumar@...aro.org; linux-kernel@...r.kernel.org; linux-pm@...r.kernel.org; cpufreq@...r.kernel.org
Subject: Re: [PATCH v2 linux-next 2/2] cpufreq: Convert the cpufreq_driver_lock to use the rcu

On Monday, February 11, 2013 05:13:30 PM Nathan Zimmer wrote:
> There are some spots that I need to give a much deeper review, cpufreq_register_driver for example.
>
> But I believe
> > @@ -196,7 +195,7 @@ static void __cpufreq_cpu_put(struct cpufreq_policy *data, bool sysfs)
> >  {
> >       if (!sysfs)
> >               kobject_put(&data->kobj);
> > -     module_put(cpufreq_driver->owner);
> > +     module_put(rcu_dereference(cpufreq_driver)->owner);
> >  }
> would be ok.  In the documentation whatisRCU.txt they give a very similar example.

Well, the very same document states the following:

        Note that the value returned by rcu_dereference() is valid
        only within the enclosing RCU read-side critical section.

Thanks,
Rafael


--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.--
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