linux-kernel - Re: Regression on cpufreq in v3.12-rc1

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Date:	Fri, 20 Sep 2013 17:36:37 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Regression on cpufreq in v3.12-rc1

On Fri, Sep 20, 2013 at 11:35 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:

> commit 389fbc3c8ad7c339cd2d9572d73c355b7b967823
> Author: Viresh Kumar <viresh.kumar@...aro.org>
> Date:   Fri Sep 20 14:55:31 2013 +0530
>
>     cpufreq: check cpufreq driver is valid and cpufreq isn't disabled
> in cpufreq_get()
>
>     cpufreq_get() can be called from external drivers which might not
> be aware if
>     cpufreq driver is registered or not. And so we should actually
> check if cpufreq
>     driver is registered or not and also if cpufreq is active or
> disabled, at the
>     beginning of cpufreq_get().
>
>     Otherwise call to lock_policy_rwsem_read() might hit BUG_ON(!policy).
>
>     Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 82ecbe3..db004a8 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1460,6 +1460,9 @@ unsigned int cpufreq_get(unsigned int cpu)
>  {
>         unsigned int ret_freq = 0;
>
> +       if (cpufreq_disabled() || !cpufreq_driver)
> +               return -ENOENT;
> +
>         if (!down_read_trylock(&cpufreq_rwsem))
>                 return 0;

This works! My system boots without crashes after this.

Tested-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij
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