linux-kernel - Re: [PATCH] cpufreq: Fix timer/workqueue corruption by protecting reading governor

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Date:	Mon, 30 Dec 2013 12:04:51 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Jane Li <jiel@...vell.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"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: Fix timer/workqueue corruption by protecting
 reading governor_enabled

On 30 December 2013 11:59, Jane Li <jiel@...vell.com> wrote:
> I checked my code, and found I lost following part.
> My local code base is not exactly same as open source, and has included
> this.
>
>
> diff --git a/drivers/cpufreq/cpufreq_governor.c
> b/drivers/cpufreq/cpufreq_governor.c
> index e6be635..c4d0ee6 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -19,6 +19,7 @@
>  #include <linux/export.h>
>  #include <linux/kernel_stat.h>
>  #include <linux/slab.h>
> +#include <linux/cpufreq.h>
>
>  #include "cpufreq_governor.h"

This shouldn't be required as cpufreq_governor.h must be including
cpufreq.h..

> Yes, I test it. After adding cpufreq_governor_lock in gov_queue_work() and
> running same test, there is no debugobjects warning.

But it really can't work at all.. There should be a separate copy of lock
in every file that includes cpufreq.h.. And so this shouldn't have worked.

> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 16d7b4a..185c9f5 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -39,7 +39,7 @@ static struct cpufreq_driver *cpufreq_driver;
>
>  static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
>  static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data_fallback);
>  static DEFINE_RWLOCK(cpufreq_driver_lock);
> -static DEFINE_MUTEX(cpufreq_governor_lock);
> +DEFINE_MUTEX(cpufreq_governor_lock);
>
>  static LIST_HEAD(cpufreq_policy_list);
>
>  #ifdef CONFIG_HOTPLUG_CPU
> diff --git a/drivers/cpufreq/cpufreq_governor.c
> b/drivers/cpufreq/cpufreq_governor.c
> index e6be635..485ee0d 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -22,6 +22,8 @@
>
>  #include "cpufreq_governor.h"
>
> +extern struct mutex cpufreq_governor_lock;
> +

Looks fine.
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