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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAKohpo=Um9LGhGtMB0z9C2jxmS3oHwV7i_Gmsq5rR80ZcGYyLw@mail.gmail.com>
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/