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Date:	Mon, 30 Dec 2013 14:29:32 +0800
From:	Jane Li <jiel@...vell.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
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 12/27/2013 05:40 PM, Viresh Kumar wrote:
> On 27 December 2013 15:00,  <jiel@...vell.com> wrote:
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> -static DEFINE_MUTEX(cpufreq_governor_lock);
>> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
>> index dc196bb..4faafe7 100644
>> --- a/include/linux/cpufreq.h
>> +++ b/include/linux/cpufreq.h
>> @@ -254,6 +254,7 @@ struct cpufreq_driver {
>>
>>   int cpufreq_register_driver(struct cpufreq_driver *driver_data);
>>   int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);
>> +static DEFINE_MUTEX(cpufreq_governor_lock);
> No way, this would never work. This would create separate locks
> in each file that includes cpufreq.h. And so the locks you are talking
> about wouldn't protect governor.

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"

> Have you actually tested this code? If this fixes the breakage you
> saw? If this fixes it then you need to do better investigation of your
> problem.

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

> you actually need to remove the static keyword from cpufreq.c file.
> Nothing else.

Modify cpufreq_governor_lock definition. Do you think it is OK?

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;
+
  static struct attribute_group *get_sysfs_attr(struct dbs_data *dbs_data)
  {
         if (have_governor_per_policy())

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