drivers/devfreq/devfreq.c | 99 +++++++++++++++++++++++---------------- 1 file changed, 58 insertions(+), 41 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 v4:
-Remove the DEFINE_SYSFS_GROUP_VISIBLE macro and directly set the is_visible function.
-Remove unnecessary ret variables
Link to v3:https://lore.kernel.org/lkml/20251107031706.1698396-1-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 | 99 +++++++++++++++++++++++----------------
1 file changed, 58 insertions(+), 41 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 2e8d01d47f69..afcfc1be2e64 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);
@@ -1807,14 +1803,16 @@ 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)
+ 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);
@@ -1828,7 +1826,10 @@ 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 +1848,10 @@ 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 +1865,10 @@ 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);
@@ -1905,37 +1912,47 @@ 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
--
2.33.0On 12/5/2025 4:37 PM, 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> Other than a few minor things that Jonathan posted, Reviewed-by: Jie Zhan <zhanjie9@hisilicon.com> Thanks! > --- > changes in v4: > -Remove the DEFINE_SYSFS_GROUP_VISIBLE macro and directly set the is_visible function. > -Remove unnecessary ret variables > Link to v3:https://lore.kernel.org/lkml/20251107031706.1698396-1-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 | 99 +++++++++++++++++++++++---------------- > 1 file changed, 58 insertions(+), 41 deletions(-) ...
On Fri, 5 Dec 2025 16:37:24 +0800
Pengjie Zhang <zhangpengjie2@huawei.com> 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,
Been a while since I looked at this series (sorry about that!)
A few trivial things inline and one suggestion for a possible follow up
patch.
None are significant enough that I'll look again at this so:
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> ---
> changes in v4:
> -Remove the DEFINE_SYSFS_GROUP_VISIBLE macro and directly set the is_visible function.
> -Remove unnecessary ret variables
> Link to v3:https://lore.kernel.org/lkml/20251107031706.1698396-1-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 | 99 +++++++++++++++++++++++----------------
> 1 file changed, 58 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 2e8d01d47f69..afcfc1be2e64 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) {
This file adopts (at least in first case I looked at) convention of no {}
when a single call is made in if blocks (even when it is multiline).
Coding standard has never been particularly clear on this corner case
so normally I'd advise following local style.
> devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_STOP, NULL);
> - remove_sysfs_files(devfreq, devfreq->governor);
> }
> -
Technically an unrelated change that I'd be temped to undo just to slightly
reduce patch size.
> 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);
Not directly relevant to this patch, but this function smells like one
that would significantly benefit from guard() and early returns in error paths.
>
> out:
> mutex_unlock(&devfreq_list_lock);
> @@ -1807,14 +1803,16 @@ static struct attribute *devfreq_attrs[] = {
> &dev_attr_trans_stat.attr,
> NULL,
> };
> @@ -1847,7 +1848,10 @@ static ssize_t timer_show(struct device *dev,
> {
> struct devfreq *df = to_devfreq(dev);
>
> - if (!df->profile)
> + guard(mutex)(&devfreq_list_lock);
For these I'd be tempted to add a trivial comment about the race they
are protecting against. I think it is the window between setting
the IS_SUPPORTED_ATTR() and isvisible being called.
> +
> + 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 +1865,10 @@ 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);
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