linux-kernel - Re: [PATCH v6 1/2] cpufreq: split the cpufreq_driver

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Message-ID: <8456428.Vj8uefv4LI@vostro.rjw.lan>
Date:	Wed, 03 Apr 2013 00:57:50 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Nathan Zimmer <nzimmer@....com>, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/2] cpufreq: split the cpufreq_driver_lock and use the rcu

On Tuesday, April 02, 2013 08:29:12 PM Viresh Kumar wrote:
> On 2 April 2013 20:25, Nathan Zimmer <nzimmer@....com> wrote:
> > 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.
> 
> Hmm.. But doesn't rcu part take care of that too?? Two writers
> updating stuff simultaneously?

RCU doesn't cover that in general.  Additional locking is needed to provide
synchronization between writers.

Thanks,
Rafael


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