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Date: Wed, 3 Apr 2013 10:55:54 +0530 From: Viresh Kumar <viresh.kumar@...aro.org> To: "Rafael J. Wysocki" <rjw@...k.pl> 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 3 April 2013 04:27, Rafael J. Wysocki <rjw@...k.pl> wrote: > 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. Hmm.. I read the same from rcu documentation now... Nathan, What about using a single spinlock (instead of two) that will take care of all locking requirements of cpufreq.c ... i.e. both cpufreq_cpu_data and cpufreq_driver_{register|unregister}... We don't need two locks actually. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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