Commit 943a872f authored by Pengjie Zhang's avatar Pengjie Zhang Committed by Chanwoo Choi
Browse files

PM / devfreq: use _visible attribute to replace create/remove_sysfs_files() 



Previously, non-generic attributes (polling_interval, timer) used separate
create/delete logic, leading to race conditions during concurrent access in
creation/deletion. Multi-threaded operations also caused inconsistencies
between governor capabilities and attribute states.

1.Use is_visible + sysfs_update_group() to unify management of these
attributes, eliminating creation/deletion races.
2.Add locks and validation to these attributes, ensuring consistency
between current governor capabilities and attribute operations in
multi-threaded environments.

Reviewed-by: default avatarJonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: default avatarJie Zhan <zhanjie9@hisilicon.com>
Signed-off-by: default avatarPengjie Zhang <zhangpengjie2@huawei.com>
Signed-off-by: default avatarChanwoo Choi <cw00.choi@samsung.com>
Link: https://www.spinics.net/lists/kernel/msg5967745.html
parent 82bb8dc9

drivers/devfreq/devfreq.c

+60 −43
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 


static struct class *devfreq_class;

static struct dentry *devfreq_debugfs;

static const struct attribute_group gov_attr_group;



/*

 * devfreq core provides delayed work based load monitoring helper
@@ -784,11 +785,6 @@ static void devfreq_dev_release(struct device *dev) 
	kfree(devfreq);

}



static void create_sysfs_files(struct devfreq *devfreq,

				const struct devfreq_governor *gov);

static void remove_sysfs_files(struct devfreq *devfreq,

				const struct devfreq_governor *gov);



/**

 * devfreq_add_device() - Add devfreq feature to the device

 * @dev:	the device to add devfreq feature.
@@ -955,7 +951,10 @@ struct devfreq *devfreq_add_device(struct device *dev, 
			 __func__);

		goto err_init;

	}

	create_sysfs_files(devfreq, devfreq->governor);



	err = sysfs_update_group(&devfreq->dev.kobj, &gov_attr_group);

	if (err)

		goto err_init;



	list_add(&devfreq->node, &devfreq_list);
@@ -994,12 +993,9 @@ int devfreq_remove_device(struct devfreq *devfreq) 


	devfreq_cooling_unregister(devfreq->cdev);



	if (devfreq->governor) {

	if (devfreq->governor)

		devfreq->governor->event_handler(devfreq,

						 DEVFREQ_GOV_STOP, NULL);

		remove_sysfs_files(devfreq, devfreq->governor);

	}



	device_unregister(&devfreq->dev);



	return 0;
@@ -1459,7 +1455,6 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr, 
			 __func__, df->governor->name, ret);

		goto out;

	}

	remove_sysfs_files(df, df->governor);



	/*

	 * Start the new governor and create the specific sysfs files
@@ -1488,7 +1483,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr, 
	 * Create the sysfs files for the new governor. But if failed to start

	 * the new governor, restore the sysfs files of previous governor.

	 */

	create_sysfs_files(df, df->governor);

	ret = sysfs_update_group(&df->dev.kobj, &gov_attr_group);



out:

	mutex_unlock(&devfreq_list_lock);
@@ -1806,14 +1801,17 @@ static struct attribute *devfreq_attrs[] = { 
	&dev_attr_trans_stat.attr,

	NULL,

};

ATTRIBUTE_GROUPS(devfreq);



static ssize_t polling_interval_show(struct device *dev,

				     struct device_attribute *attr, char *buf)

{

	struct devfreq *df = to_devfreq(dev);



	if (!df->profile)

	/* Protect against race between sysfs attrs update and read/write */

	guard(mutex)(&devfreq_list_lock);



	if (!df->profile || !df->governor ||

	    !IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))

		return -EINVAL;



	return sprintf(buf, "%d\n", df->profile->polling_ms);
@@ -1827,7 +1825,10 @@ static ssize_t polling_interval_store(struct device *dev, 
	unsigned int value;

	int ret;



	if (!df->governor)

	guard(mutex)(&devfreq_list_lock);



	if (!df->governor ||

	    !IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))

		return -EINVAL;



	ret = sscanf(buf, "%u", &value);
@@ -1846,7 +1847,10 @@ static ssize_t timer_show(struct device *dev, 
{

	struct devfreq *df = to_devfreq(dev);



	if (!df->profile)

	guard(mutex)(&devfreq_list_lock);



	if (!df->profile || !df->governor ||

	    !IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))

		return -EINVAL;



	return sprintf(buf, "%s\n", timer_name[df->profile->timer]);
@@ -1860,7 +1864,10 @@ static ssize_t timer_store(struct device *dev, struct device_attribute *attr, 
	int timer = -1;

	int ret = 0, i;



	if (!df->governor || !df->profile)

	guard(mutex)(&devfreq_list_lock);



	if (!df->governor || !df->profile ||

	    !IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))

		return -EINVAL;



	ret = sscanf(buf, "%16s", str_timer);
@@ -1904,37 +1911,47 @@ static ssize_t timer_store(struct device *dev, struct device_attribute *attr, 
}

static DEVICE_ATTR_RW(timer);



#define CREATE_SYSFS_FILE(df, name)					\

{									\

	int ret;							\

	ret = sysfs_create_file(&df->dev.kobj, &dev_attr_##name.attr);	\

	if (ret < 0) {							\

		dev_warn(&df->dev,					\

			"Unable to create attr(%s)\n", "##name");	\

	}								\

}									\

static struct attribute *governor_attrs[] = {

	&dev_attr_polling_interval.attr,

	&dev_attr_timer.attr,

	NULL

};



/* Create the specific sysfs files which depend on each governor. */

static void create_sysfs_files(struct devfreq *devfreq,

				const struct devfreq_governor *gov)

static umode_t gov_attr_visible(struct kobject *kobj,

				struct attribute *attr, int n)

{

	if (IS_SUPPORTED_ATTR(gov->attrs, POLLING_INTERVAL))

		CREATE_SYSFS_FILE(devfreq, polling_interval);

	if (IS_SUPPORTED_ATTR(gov->attrs, TIMER))

		CREATE_SYSFS_FILE(devfreq, timer);

}

	struct device *dev = kobj_to_dev(kobj);

	struct devfreq *df = to_devfreq(dev);



/* Remove the specific sysfs files which depend on each governor. */

static void remove_sysfs_files(struct devfreq *devfreq,

				const struct devfreq_governor *gov)

{

	if (IS_SUPPORTED_ATTR(gov->attrs, POLLING_INTERVAL))

		sysfs_remove_file(&devfreq->dev.kobj,

				&dev_attr_polling_interval.attr);

	if (IS_SUPPORTED_ATTR(gov->attrs, TIMER))

		sysfs_remove_file(&devfreq->dev.kobj, &dev_attr_timer.attr);

	if (!df->governor || !df->governor->attrs)

		return 0;



	if (attr == &dev_attr_polling_interval.attr &&

	    IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))

		return attr->mode;



	if (attr == &dev_attr_timer.attr &&

	    IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))

		return attr->mode;



	return 0;

}



static const struct attribute_group devfreq_group = {

	.attrs = devfreq_attrs,

};



static const struct attribute_group gov_attr_group = {

	.attrs = governor_attrs,

	.is_visible = gov_attr_visible,

};



static const struct attribute_group *devfreq_groups[] = {

	&devfreq_group,

	&gov_attr_group,

	NULL

};



/**

 * devfreq_summary_show() - Show the summary of the devfreq devices

 * @s:		seq_file instance to show the summary of devfreq devices