linux-kernel - Re: [PATCH] Cpufreq: Acquire read lock in the cpufreq_policy

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Date:	Wed, 11 Sep 2013 14:14:50 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.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: [PATCH] Cpufreq: Acquire read lock in the cpufreq_policy_restore()
 rather than write lock

On 11 September 2013 12:35,  <tianyu.lan@...el.com> wrote:
> From: Lan Tianyu <tianyu.lan@...el.com>
>
> In the cpufreq_policy_restore(), policy before system suspend is read from
> from percpu's cpufreq_cpu_data_fallback. It's read operation rather than
> write operation. So convert write lock to read lock
>
> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>
> ---
>  drivers/cpufreq/cpufreq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 81ceea6..b762f9b 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -912,11 +912,11 @@ static struct cpufreq_policy *cpufreq_policy_restore(unsigned int cpu)
>         struct cpufreq_policy *policy;
>         unsigned long flags;
>
> -       write_lock_irqsave(&cpufreq_driver_lock, flags);
> +       read_lock_irqsave(&cpufreq_driver_lock, flags);
>
>         policy = per_cpu(cpufreq_cpu_data_fallback, cpu);
>
> -       write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> +       read_unlock_irqrestore(&cpufreq_driver_lock, flags);
>
>         return policy;
>  }

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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