RE: [PATCH v2 linux-next 2/2] cpufreq: Convert thecpufreq_driver_lock to use the rcu

From: Nathan Zimmer
Date: Mon Feb 11 2013 - 23:03:49 EST

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


From: Rafael J. Wysocki [rjw@xxxxxxx]
Sent: Monday, February 11, 2013 1:36 PM
To: Nathan Zimmer
Cc: viresh.kumar@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-pm@xxxxxxxxxxxxxxx; cpufreq@xxxxxxxxxxxxxxx
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.


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