Re: [PATCH v6 1/2] cpufreq: split the cpufreq_driver_lock and usethe rcu

[Nathan Zimmer]

On Tue, Apr 02, 2013 at 10:35:46AM +0530, Viresh Kumar wrote:
> On 2 April 2013 01:41, Nathan Zimmer <nzimmer@xxxxxxx> wrote:
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> 
> > +static struct cpufreq_driver __rcu *cpufreq_driver;
> > +static DEFINE_SPINLOCK(cpufreq_driver_lock);
> 
> You really need this lock? This is only used in cpufreq_register_driver
> and unregister_driver... And it doesn't protect other routines at all. And
> because we are using rcu stuff now, probably this lock is just not required.
> 
The lock is unneeded if we expect register and unregister driver to not be
called from muliple threads at once.  I didn't make that assumption.

> > +static DEFINE_SPINLOCK(cpufreq_data_lock);
> 
> Only this one is required and it can be the rwlock which is already pushed
> by rafael.
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