drivers/devfreq/devfreq.c | 108 ++++++++++++++++++++++++-------------- 1 file changed, 68 insertions(+), 40 deletions(-)
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.
Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
---
changes in v3:
- Use guard() to simplify lock acquisition and destruction.
- Eliminate redundant checks for df.
Link to v2:https://lore.kernel.org/lkml/20251028022458.2824872-1-zhangpengjie2@huawei.com/
Changes in v2:
- Fix one problem reported by the kernel test robot.
- Redirect all error paths in timer_store() to out to ensure locks are not
left unReleased.
Link to v1:https://lore.kernel.org/lkml/20251025135238.3576861-1-zhangpengjie2@huawei.com/
drivers/devfreq/devfreq.c | 108 ++++++++++++++++++++++++--------------
1 file changed, 68 insertions(+), 40 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 2e8d01d47f69..674b794d553d 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -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
@@ -785,11 +786,6 @@ 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.
@@ -956,7 +952,10 @@ 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);
@@ -998,9 +997,7 @@ int devfreq_remove_device(struct devfreq *devfreq)
if (devfreq->governor) {
devfreq->governor->event_handler(devfreq,
DEVFREQ_GOV_STOP, NULL);
- remove_sysfs_files(devfreq, devfreq->governor);
}
-
device_unregister(&devfreq->dev);
return 0;
@@ -1460,7 +1457,6 @@ 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
@@ -1489,7 +1485,7 @@ 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);
@@ -1807,17 +1803,22 @@ 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);
+ int ret;
- if (!df->profile)
+ 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);
+ ret = sprintf(buf, "%d\n", df->profile->polling_ms);
+
+ return ret;
}
static ssize_t polling_interval_store(struct device *dev,
@@ -1828,7 +1829,10 @@ 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);
@@ -1847,7 +1851,10 @@ 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]);
@@ -1861,7 +1868,10 @@ 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);
@@ -1905,36 +1915,54 @@ 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);
+
+ if (!df->governor || !df->governor->attrs)
+ return 0;
+
+ if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
+ return attr->mode;
+ if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
+ return attr->mode;
+
+ return 0;
}
-/* Remove the specific sysfs files which depend on each governor. */
-static void remove_sysfs_files(struct devfreq *devfreq,
- const struct devfreq_governor *gov)
+static bool gov_group_visible(struct kobject *kobj)
{
- 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);
+ struct device *dev = kobj_to_dev(kobj);
+
+ if (!dev)
+ return false;
+
+ return true;
}
+DEFINE_SYSFS_GROUP_VISIBLE(gov);
+
+static const struct attribute_group devfreq_group = {
+ .attrs = devfreq_attrs,
+};
+
+static const struct attribute_group gov_attr_group = {
+ .attrs = governor_attrs,
+ .is_visible = SYSFS_GROUP_VISIBLE(gov),
+};
+
+static const struct attribute_group *devfreq_groups[] = {
+ &devfreq_group,
+ &gov_attr_group,
+ NULL
+};
/**
* devfreq_summary_show() - Show the summary of the devfreq devices
--
2.33.0
On 11/7/2025 11:17 AM, Pengjie Zhang wrote:
> 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.
>
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
Hi Pengjie,
The motivation looks fine but the implementation of gov_group_visible() and
gov_attr_visible() doesn't work right in my view.
See comments below.
Thanks!
Jie
> ---
> changes in v3:
> - Use guard() to simplify lock acquisition and destruction.
> - Eliminate redundant checks for df.
> Link to v2:https://lore.kernel.org/lkml/20251028022458.2824872-1-zhangpengjie2@huawei.com/
>
> Changes in v2:
> - Fix one problem reported by the kernel test robot.
> - Redirect all error paths in timer_store() to out to ensure locks are not
> left unReleased.
> Link to v1:https://lore.kernel.org/lkml/20251025135238.3576861-1-zhangpengjie2@huawei.com/
>
> drivers/devfreq/devfreq.c | 108 ++++++++++++++++++++++++--------------
> 1 file changed, 68 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 2e8d01d47f69..674b794d553d 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -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
> @@ -785,11 +786,6 @@ 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.
> @@ -956,7 +952,10 @@ 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);
>
> @@ -998,9 +997,7 @@ int devfreq_remove_device(struct devfreq *devfreq)
> if (devfreq->governor) {
> devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_STOP, NULL);
> - remove_sysfs_files(devfreq, devfreq->governor);
> }
> -
> device_unregister(&devfreq->dev);
>
> return 0;
> @@ -1460,7 +1457,6 @@ 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
> @@ -1489,7 +1485,7 @@ 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);
> @@ -1807,17 +1803,22 @@ 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);
> + int ret;
No need of this if restore the last line.
>
> - if (!df->profile)
> + 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);
It's fine to keep this line.
> + ret = sprintf(buf, "%d\n", df->profile->polling_ms);
> +
> + return ret;
> }
>
> static ssize_t polling_interval_store(struct device *dev,
> @@ -1828,7 +1829,10 @@ 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);
> @@ -1847,7 +1851,10 @@ 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]);
> @@ -1861,7 +1868,10 @@ 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);
> @@ -1905,36 +1915,54 @@ 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);
> +
> + if (!df->governor || !df->governor->attrs)
> + return 0;
> +
> + if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
> + return attr->mode;
> + if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
> + return attr->mode;
This would expose both 'timer' and 'polling_interval' if either of them is
supported, which is wrong.
> +
> + return 0;
> }
>
> -/* Remove the specific sysfs files which depend on each governor. */
> -static void remove_sysfs_files(struct devfreq *devfreq,
> - const struct devfreq_governor *gov)
> +static bool gov_group_visible(struct kobject *kobj)
> {
> - 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);
> + struct device *dev = kobj_to_dev(kobj);
> +
> + if (!dev)
> + return false;
kobj_to_dev(kobj) can't fail. This check is unnecessary.
> +
> + return true;
> }
> +DEFINE_SYSFS_GROUP_VISIBLE(gov);
The implementation of gov_group_visible() and gov_attr_visible() doesn't
seem to comply with the design of DEFINE_SYSFS_GROUP_VISIBLE().
DEFINE_SYSFS_GROUP_VISIBLE is defined as:
#define DEFINE_SYSFS_GROUP_VISIBLE(name) \
static inline umode_t sysfs_group_visible_##name( \
struct kobject *kobj, struct attribute *attr, int n) \
{ \
if (n == 0 && !name##_group_visible(kobj)) \
return SYSFS_GROUP_INVISIBLE; \
return name##_attr_visible(kobj, attr, n); \
}
That means:
_group_visible controls whether to hide all the attrs in this group;
_attr_visible further decides whether to show each attr.
Hence,
1. gov_group_visible() should check if any attr in 'governor_attrs' should
be present, i.e. checking df->governor->attrs.
2. gov_attr_visible identifies which attr it is and checks whether the
governor supports it.
Neither is done in the above code, so this should be updated.
> +
> +static const struct attribute_group devfreq_group = {
> + .attrs = devfreq_attrs,
> +};
> +
> +static const struct attribute_group gov_attr_group = {
> + .attrs = governor_attrs,
> + .is_visible = SYSFS_GROUP_VISIBLE(gov),
> +};
> +
> +static const struct attribute_group *devfreq_groups[] = {
> + &devfreq_group,
> + &gov_attr_group,
> + NULL
> +};
>
> /**
> * devfreq_summary_show() - Show the summary of the devfreq devices
hello，Jie
On 12/4/2025 3:36 PM, Jie Zhan wrote:
> On 11/7/2025 11:17 AM, Pengjie Zhang wrote:
>> 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.
>>
>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> Hi Pengjie,
>
> The motivation looks fine but the implementation of gov_group_visible() and
> gov_attr_visible() doesn't work right in my view.
>
> See comments below.
>
> Thanks!
> Jie
>> /*
>> * devfreq core provides delayed work based load monitoring helper
>> @@ -785,11 +786,6 @@ static void devfreq_dev_release(struct device *dev)
>> kfree(devfreq);
>> }
>>
>>
>> static ssize_t polling_interval_show(struct device *dev,
>> struct device_attribute *attr, char *buf)
>> {
>> struct devfreq *df = to_devfreq(dev);
>> + int ret;
> No need of this if restore the last line.
>>
>> - if (!df->profile)
>> + 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);
> It's fine to keep this line.
>> + ret = sprintf(buf, "%d\n", df->profile->polling_ms);
>> +
>> + return ret;
>> }
>>
>>
>>
>> -/* 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);
>> +
>> + if (!df->governor || !df->governor->attrs)
>> + return 0;
>> +
>> + if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
>> + return attr->mode;
>> + if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
>> + return attr->mode;
> This would expose both 'timer' and 'polling_interval' if either of them is
> supported, which is wrong.
ok，i see，may be
if (attr == &dev_attr_polling_interval.attr) {
if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
return attr->mode;
return 0;
}
if (attr == &dev_attr_timer.attr) {
if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
return attr->mode;
return 0;
}
>> +
>> + return 0;
>> }
>>
>> -/* Remove the specific sysfs files which depend on each governor. */
>> -static void remove_sysfs_files(struct devfreq *devfreq,
>> - const struct devfreq_governor *gov)
>> +static bool gov_group_visible(struct kobject *kobj)
>> {
>> - 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);
>> + struct device *dev = kobj_to_dev(kobj);
>> +
>> + if (!dev)
>> + return false;
> kobj_to_dev(kobj) can't fail. This check is unnecessary.
>> +
>> + return true;
>> }
>> +DEFINE_SYSFS_GROUP_VISIBLE(gov);
> The implementation of gov_group_visible() and gov_attr_visible() doesn't
> seem to comply with the design of DEFINE_SYSFS_GROUP_VISIBLE().
>
> DEFINE_SYSFS_GROUP_VISIBLE is defined as:
>
> #define DEFINE_SYSFS_GROUP_VISIBLE(name) \
> static inline umode_t sysfs_group_visible_##name( \
> struct kobject *kobj, struct attribute *attr, int n) \
> { \
> if (n == 0 && !name##_group_visible(kobj)) \
> return SYSFS_GROUP_INVISIBLE; \
> return name##_attr_visible(kobj, attr, n); \
> }
>
> That means:
> _group_visible controls whether to hide all the attrs in this group;
> _attr_visible further decides whether to show each attr.
>
> Hence,
> 1. gov_group_visible() should check if any attr in 'governor_attrs' should
> be present, i.e. checking df->governor->attrs.
> 2. gov_attr_visible identifies which attr it is and checks whether the
> governor supports it.
>
> Neither is done in the above code, so this should be updated.
we can move the check|if (!df->governor || !df->governor->attrs)|
from|gov_attr_visible|to|gov_group_visible|.
thanks !
...
>>> +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);
>>> +
>>> + if (!df->governor || !df->governor->attrs)
>>> + return 0;
>>> +
>>> + if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
>>> + return attr->mode;
>>> + if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
>>> + return attr->mode;
>> This would expose both 'timer' and 'polling_interval' if either of them is
>> supported, which is wrong.
>
> ok，i see，may be
>
> if (attr == &dev_attr_polling_interval.attr) {
> if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
> return attr->mode;
> return 0;
> }
>
> if (attr == &dev_attr_timer.attr) {
> if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
> return attr->mode;
> return 0;
> }
>
Yeah.
Could be cleaner like:
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;
}
>>> +
>>> + return 0;
>>> }
>>> -/* Remove the specific sysfs files which depend on each governor. */
>>> -static void remove_sysfs_files(struct devfreq *devfreq,
>>> - const struct devfreq_governor *gov)
>>> +static bool gov_group_visible(struct kobject *kobj)
>>> {
>>> - 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);
>>> + struct device *dev = kobj_to_dev(kobj);
>>> +
>>> + if (!dev)
>>> + return false;
>> kobj_to_dev(kobj) can't fail. This check is unnecessary.
>>> +
>>> + return true;
>>> }
>>> +DEFINE_SYSFS_GROUP_VISIBLE(gov);
>> The implementation of gov_group_visible() and gov_attr_visible() doesn't
>> seem to comply with the design of DEFINE_SYSFS_GROUP_VISIBLE().
>>
>> DEFINE_SYSFS_GROUP_VISIBLE is defined as:
>>
>> #define DEFINE_SYSFS_GROUP_VISIBLE(name) \
>> static inline umode_t sysfs_group_visible_##name( \
>> struct kobject *kobj, struct attribute *attr, int n) \
>> { \
>> if (n == 0 && !name##_group_visible(kobj)) \
>> return SYSFS_GROUP_INVISIBLE; \
>> return name##_attr_visible(kobj, attr, n); \
>> }
>>
>> That means:
>> _group_visible controls whether to hide all the attrs in this group;
>> _attr_visible further decides whether to show each attr.
>>
>> Hence,
>> 1. gov_group_visible() should check if any attr in 'governor_attrs' should
>> be present, i.e. checking df->governor->attrs.
>> 2. gov_attr_visible identifies which attr it is and checks whether the
>> governor supports it.
>>
>> Neither is done in the above code, so this should be updated.
>
> we can move the check|if (!df->governor || !df->governor->attrs)|
>
> from|gov_attr_visible|to|gov_group_visible|.
Exactly.
>
> thanks !
>
Gentle ping .
Thanks!
On 11/7/2025 11:17 AM, Pengjie Zhang wrote:
> 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.
>
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> ---
> changes in v3:
> - Use guard() to simplify lock acquisition and destruction.
> - Eliminate redundant checks for df.
> Link to v2:https://lore.kernel.org/lkml/20251028022458.2824872-1-zhangpengjie2@huawei.com/
>
> Changes in v2:
> - Fix one problem reported by the kernel test robot.
> - Redirect all error paths in timer_store() to out to ensure locks are not
> left unReleased.
> Link to v1:https://lore.kernel.org/lkml/20251025135238.3576861-1-zhangpengjie2@huawei.com/
>
> drivers/devfreq/devfreq.c | 108 ++++++++++++++++++++++++--------------
> 1 file changed, 68 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 2e8d01d47f69..674b794d553d 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -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
> @@ -785,11 +786,6 @@ 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.
> @@ -956,7 +952,10 @@ 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);
>
> @@ -998,9 +997,7 @@ int devfreq_remove_device(struct devfreq *devfreq)
> if (devfreq->governor) {
> devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_STOP, NULL);
> - remove_sysfs_files(devfreq, devfreq->governor);
> }
> -
> device_unregister(&devfreq->dev);
>
> return 0;
> @@ -1460,7 +1457,6 @@ 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
> @@ -1489,7 +1485,7 @@ 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);
> @@ -1807,17 +1803,22 @@ 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);
> + int ret;
>
> - if (!df->profile)
> + 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);
> + ret = sprintf(buf, "%d\n", df->profile->polling_ms);
> +
> + return ret;
> }
>
> static ssize_t polling_interval_store(struct device *dev,
> @@ -1828,7 +1829,10 @@ 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);
> @@ -1847,7 +1851,10 @@ 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]);
> @@ -1861,7 +1868,10 @@ 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);
> @@ -1905,36 +1915,54 @@ 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);
> +
> + if (!df->governor || !df->governor->attrs)
> + return 0;
> +
> + if (IS_SUPPORTED_ATTR(df->governor->attrs, POLLING_INTERVAL))
> + return attr->mode;
> + if (IS_SUPPORTED_ATTR(df->governor->attrs, TIMER))
> + return attr->mode;
> +
> + return 0;
> }
>
> -/* Remove the specific sysfs files which depend on each governor. */
> -static void remove_sysfs_files(struct devfreq *devfreq,
> - const struct devfreq_governor *gov)
> +static bool gov_group_visible(struct kobject *kobj)
> {
> - 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);
> + struct device *dev = kobj_to_dev(kobj);
> +
> + if (!dev)
> + return false;
> +
> + return true;
> }
> +DEFINE_SYSFS_GROUP_VISIBLE(gov);
> +
> +static const struct attribute_group devfreq_group = {
> + .attrs = devfreq_attrs,
> +};
> +
> +static const struct attribute_group gov_attr_group = {
> + .attrs = governor_attrs,
> + .is_visible = SYSFS_GROUP_VISIBLE(gov),
> +};
> +
> +static const struct attribute_group *devfreq_groups[] = {
> + &devfreq_group,
> + &gov_attr_group,
> + NULL
> +};
>
> /**
> * devfreq_summary_show() - Show the summary of the devfreq devices
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