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[RFC PATCH 07/19] cpufreq: assert locking when accessing cpufreq_governor_list

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  [RFC PATCH 07/19] cpufreq: assert locking when accessing cpufreq_governor_list Juri Lelli <juri.lelli@arm.com> - 2016-01-11 18:50 +0100
    Re: [RFC PATCH 07/19] cpufreq: assert locking when accessing  cpufreq_governor_list Viresh Kumar <viresh.kumar@linaro.org> - 2016-01-12 11:10 +0100
      Re: [RFC PATCH 07/19] cpufreq: assert locking when accessing  cpufreq_governor_list Juri Lelli <juri.lelli@arm.com> - 2016-01-12 16:40 +0100

#1306565 — [RFC PATCH 07/19] cpufreq: assert locking when accessing cpufreq_governor_list

cpufreq_governor_list is guarded by cpufreq_governor_mutex. Add
appropriate locking assertions to check that we always access the list
while holding the lock protecting it.

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
---
 drivers/cpufreq/cpufreq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 98adbc2..7dae7f3 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -506,6 +506,7 @@ static struct cpufreq_governor *find_governor(const char *str_governor)
 {
 	struct cpufreq_governor *t;
 
+	lockdep_assert_held(&cpufreq_governor_mutex);
 	for_each_governor(t)
 		if (!strncasecmp(str_governor, t->name, CPUFREQ_NAME_LEN))
 			return t;
@@ -693,6 +694,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy,
 		goto out;
 	}
 
+	lockdep_assert_held(&cpufreq_governor_mutex);
 	for_each_governor(t) {
 		if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char))
 		    - (CPUFREQ_NAME_LEN + 2)))
@@ -2025,6 +2027,7 @@ int cpufreq_register_governor(struct cpufreq_governor *governor)
 	err = -EBUSY;
 	if (!find_governor(governor->name)) {
 		err = 0;
+		lockdep_assert_held(&cpufreq_governor_mutex);
 		list_add(&governor->governor_list, &cpufreq_governor_list);
 	}
 
-- 
2.2.2

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#1307195 — Re: [RFC PATCH 07/19] cpufreq: assert locking when accessing cpufreq_governor_list

On 11-01-16, 17:35, Juri Lelli wrote:
> @@ -2025,6 +2027,7 @@ int cpufreq_register_governor(struct cpufreq_governor *governor)
>  	err = -EBUSY;
>  	if (!find_governor(governor->name)) {
>  		err = 0;
> +		lockdep_assert_held(&cpufreq_governor_mutex);
>  		list_add(&governor->governor_list, &cpufreq_governor_list);
>  	}

Why here? This is how the routine looks like:

int cpufreq_register_governor(struct cpufreq_governor *governor)
{
	int err;

	if (!governor)
		return -EINVAL;

	if (cpufreq_disabled())
		return -ENODEV;

	mutex_lock(&cpufreq_governor_mutex);

	governor->initialized = 0;
	err = -EBUSY;
	if (!find_governor(governor->name)) {
		err = 0;
		list_add(&governor->governor_list, &cpufreq_governor_list);
	}

	mutex_unlock(&cpufreq_governor_mutex);
	return err;
}


-- 
viresh

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#1307563 — Re: [RFC PATCH 07/19] cpufreq: assert locking when accessing cpufreq_governor_list

Hi,

On 12/01/16 15:31, Viresh Kumar wrote:
> On 11-01-16, 17:35, Juri Lelli wrote:
> > @@ -2025,6 +2027,7 @@ int cpufreq_register_governor(struct cpufreq_governor *governor)
> >  	err = -EBUSY;
> >  	if (!find_governor(governor->name)) {
> >  		err = 0;
> > +		lockdep_assert_held(&cpufreq_governor_mutex);
> >  		list_add(&governor->governor_list, &cpufreq_governor_list);
> >  	}
> 
> Why here? This is how the routine looks like:
> 

I guess I was simply over-paranoid. We can drop this assertion.

Thanks,

- Juri

> int cpufreq_register_governor(struct cpufreq_governor *governor)
> {
> 	int err;
> 
> 	if (!governor)
> 		return -EINVAL;
> 
> 	if (cpufreq_disabled())
> 		return -ENODEV;
> 
> 	mutex_lock(&cpufreq_governor_mutex);
> 
> 	governor->initialized = 0;
> 	err = -EBUSY;
> 	if (!find_governor(governor->name)) {
> 		err = 0;
> 		list_add(&governor->governor_list, &cpufreq_governor_list);
> 	}
> 
> 	mutex_unlock(&cpufreq_governor_mutex);
> 	return err;
> }
> 
> 
> -- 
> viresh
> 

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