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Commit 902ad8fa authored by Rama Aparna Mallavarapu's avatar Rama Aparna Mallavarapu Committed by Saravana Kannan
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ANDROID: GKI: PM / devfreq: Fix race condition between suspend/resume and governor_store 



There is a race condition when the event governor_store is being executed
from sysfs and the device issues a suspend. The devfreq data structures
would become stale when the suspend tries to access them in the middle
of the governor_store operation. Fix this issue by taking a lock around
suspend and resume operations so that these operations are not concurrent
with the other events from sysfs.

Also rename the sysfs_lock as event_lock since the same lock is used
for non sysfs operations like suspend and resume as well.

Change-Id: Ifa0e93915a920cec3e0429966328a1128d61098b
Signed-off-by: default avatarRama Aparna Mallavarapu <aparnam@codeaurora.org>
Bug: 152343889
(cherry picked from commit 8bf200e7)
Signed-off-by: default avatarSaravana Kannan <saravanak@google.com>
parent 8f43993c

drivers/devfreq/devfreq.c

+21 −12
Original line number Diff line number Diff line
@@ -582,7 +582,7 @@ static void devfreq_dev_release(struct device *dev) 
		devfreq->profile->exit(devfreq->dev.parent);



	mutex_destroy(&devfreq->lock);

	mutex_destroy(&devfreq->sysfs_lock);

	mutex_destroy(&devfreq->event_lock);

	kfree(devfreq);

}
@@ -625,7 +625,7 @@ struct devfreq *devfreq_add_device(struct device *dev, 
	}



	mutex_init(&devfreq->lock);

	mutex_init(&devfreq->sysfs_lock);

	mutex_init(&devfreq->event_lock);

	mutex_lock(&devfreq->lock);

	devfreq->dev.parent = dev;

	devfreq->dev.class = devfreq_class;
@@ -862,14 +862,19 @@ EXPORT_SYMBOL(devm_devfreq_remove_device); 
 */

int devfreq_suspend_device(struct devfreq *devfreq)

{

	int ret;



	if (!devfreq)

		return -EINVAL;



	if (!devfreq->governor)

		return 0;



	return devfreq->governor->event_handler(devfreq,

	mutex_lock(&devfreq->event_lock);

	ret = devfreq->governor->event_handler(devfreq,

				DEVFREQ_GOV_SUSPEND, NULL);

	mutex_unlock(&devfreq->event_lock);

	return ret;

}

EXPORT_SYMBOL(devfreq_suspend_device);
@@ -883,14 +888,18 @@ EXPORT_SYMBOL(devfreq_suspend_device); 
 */

int devfreq_resume_device(struct devfreq *devfreq)

{

	int ret;

	if (!devfreq)

		return -EINVAL;



	if (!devfreq->governor)

		return 0;



	return devfreq->governor->event_handler(devfreq,

	mutex_lock(&devfreq->event_lock);

	ret = devfreq->governor->event_handler(devfreq,

				DEVFREQ_GOV_RESUME, NULL);

	mutex_unlock(&devfreq->event_lock);

	return ret;

}

EXPORT_SYMBOL(devfreq_resume_device);
@@ -1058,7 +1067,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr, 
		goto out;

	}



	mutex_lock(&df->sysfs_lock);

	mutex_lock(&df->event_lock);

	if (df->governor) {

		ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);

		if (ret) {
@@ -1075,7 +1084,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr, 
			 __func__, df->governor->name, ret);



gov_stop_out:

	mutex_unlock(&df->sysfs_lock);

	mutex_unlock(&df->event_lock);

out:

	mutex_unlock(&devfreq_list_lock);
@@ -1170,10 +1179,10 @@ static ssize_t polling_interval_store(struct device *dev, 
	if (ret != 1)

		return -EINVAL;



	mutex_lock(&df->sysfs_lock);

	mutex_lock(&df->event_lock);

	df->governor->event_handler(df, DEVFREQ_GOV_INTERVAL, &value);

	ret = count;

	mutex_unlock(&df->sysfs_lock);

	mutex_unlock(&df->event_lock);



	return ret;

}
@@ -1190,7 +1199,7 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr, 
	if (ret != 1)

		return -EINVAL;



	mutex_lock(&df->sysfs_lock);

	mutex_lock(&df->event_lock);

	mutex_lock(&df->lock);



	if (value) {
@@ -1213,7 +1222,7 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr, 
	ret = count;

unlock:

	mutex_unlock(&df->lock);

	mutex_unlock(&df->sysfs_lock);

	mutex_unlock(&df->event_lock);

	return ret;

}
@@ -1236,7 +1245,7 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr, 
	if (ret != 1)

		return -EINVAL;



	mutex_lock(&df->sysfs_lock);

	mutex_lock(&df->event_lock);

	mutex_lock(&df->lock);



	if (value) {
@@ -1259,7 +1268,7 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr, 
	ret = count;

unlock:

	mutex_unlock(&df->lock);

	mutex_unlock(&df->sysfs_lock);

	mutex_unlock(&df->event_lock);

	return ret;

}

static DEVICE_ATTR_RW(min_freq);

include/linux/devfreq.h

+1 −1
Original line number Diff line number Diff line
@@ -149,7 +149,7 @@ struct devfreq { 
	struct list_head node;



	struct mutex lock;

	struct mutex sysfs_lock;

	struct mutex event_lock;

	struct device dev;

	struct devfreq_dev_profile *profile;

	const struct devfreq_governor *governor;