linux-kernel - Re: [PATCH] cpufreq: remove sysfs files for CPU which failed to come back after resume

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Message-ID: <2118684.kuZSLHD0UA@vostro.rjw.lan>
Date:	Fri, 20 Dec 2013 16:14:57 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	linaro-kernel@...ts.linaro.org, patches@...aro.org,
	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com
Subject: Re: [PATCH] cpufreq: remove sysfs files for CPU which failed to come back after resume

On Friday, December 20, 2013 10:38:20 AM Viresh Kumar wrote:
> There are cases where cpufreq_add_dev() may fail for some CPUs during resume.
> With the current code we will still have sysfs cpufreq files for such CPUs, and
> struct cpufreq_policy would be already freed for them. Hence any operation on
> those sysfs files would result in kernel warnings.
> 
> To fix this, lets remove those sysfs files or put the associated kobject in case
> of such errors. Also, to make it simple lets remove the sysfs links from all the
> CPUs (except policy->cpu) during suspend as that operation wouldn't result with a
> loss of sysfs file permissions. And so we will create those links during resume
> as well.
> 
> Reported-and-tested-by: Bjørn Mork <bjorn@...k.no>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 61 ++++++++++++++++++++++++-----------------------
>  1 file changed, 31 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 02d534d..cea96c9 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -845,8 +845,7 @@ static void cpufreq_init_policy(struct cpufreq_policy *policy)
>  
>  #ifdef CONFIG_HOTPLUG_CPU
>  static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
> -				  unsigned int cpu, struct device *dev,
> -				  bool frozen)
> +				  unsigned int cpu, struct device *dev)
>  {
>  	int ret = 0;
>  	unsigned long flags;
> @@ -877,9 +876,7 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
>  		}
>  	}
>  
> -	/* Don't touch sysfs links during light-weight init */
> -	if (!frozen)
> -		ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
> +	ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
>  
>  	return ret;
>  }

Well, this just looks odd.  Please do

	return sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");

And I'm fine with the rest of the patch.

Thanks,
Rafael

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