linux-kernel - Re: [cpufreq] swapper/1 is trying to release lock cpufreq_rwsem at cpufreq_add

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Date:	Tue, 20 Aug 2013 21:16:53 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [cpufreq] swapper/1 is trying to release lock cpufreq_rwsem at cpufreq_add_dev()

On 20 August 2013 21:04, Fengguang Wu <fengguang.wu@...el.com> wrote:
> Greetings,
>
> I got the below dmesg and the first bad commit is
>
> commit 6eed9404ab3c4baea54ce4c7e862e69df1d39f38
> Author: Viresh Kumar <viresh.kumar@...aro.org>
> Date:   Tue Aug 6 22:53:11 2013 +0530
>
>     cpufreq: Use rwsem for protecting critical sections
>
>     Critical sections of the cpufreq core are protected with the help of
>     the driver module owner's refcount, which isn't the correct approach,
>     because it causes rmmod to return an error when some routine has
>     updated that refcount.
>
>     Let's use rwsem for this purpose instead.  Only
>     cpufreq_unregister_driver() will use write sem
>     and everybody else will use read sem.
>
>     [rjw: Subject & changelog]
>     Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
>     Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Somebody reported similar stuff with a fix but sent it to wrong
mailing list. Can you
try attached patch?

View attachment "cpufreq: fix bad unlock balance on !CONFIG_SMP.txt" of type "text/plain" (6845 bytes)