[PATCH v1] leds: introduce ordered workqueue for leds events instead of system_wq

[PATCH v1] leds: introduce ordered workqueue for leds events instead of system_wq

[Dmitry Rokosov]

This allows to setup ordered workqueue for leds events. This may be
useful, because default 'system_wq' does not guarantee execution order
of each work_struct, thus for several brightness update requests (for
multiple leds), real brightness switch could be in random order.

Yes, for sysfs-based leds we have flush_work() call inside
brightness_store() operation, but it's blocking call, so userspace
caller can be blocked at a long time, which means leds animation stream
can be broken.

Ordered workqueue has the same behaviour as system_wq + flush_work(),
but all scheduled works are async and userspace caller is not blocked,
which it better for userspace animation scheduling.

Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
---
 drivers/leds/led-class.c | 12 +++++++++++-
 drivers/leds/led-core.c  |  6 +++---
 include/linux/leds.h     |  1 +
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index ba1be15cfd8e..fba12471cf1f 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -25,6 +25,8 @@
 static DEFINE_MUTEX(leds_lookup_lock);
 static LIST_HEAD(leds_lookup_list);
 
+static struct workqueue_struct *leds_wq;
+
 static ssize_t brightness_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -57,7 +59,6 @@ static ssize_t brightness_store(struct device *dev,
 	if (state == LED_OFF)
 		led_trigger_remove(led_cdev);
 	led_set_brightness(led_cdev, state);
-	flush_work(&led_cdev->set_brightness_work);
 
 	ret = size;
 unlock:
@@ -549,6 +550,8 @@ int led_classdev_register_ext(struct device *parent,
 
 	led_update_brightness(led_cdev);
 
+	led_cdev->wq = leds_wq;
+
 	led_init_core(led_cdev);
 
 #ifdef CONFIG_LEDS_TRIGGERS
@@ -667,12 +670,19 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
 
 static int __init leds_init(void)
 {
+	leds_wq = alloc_ordered_workqueue("leds", 0);
+	if (!leds_wq) {
+		pr_err("failed to create leds ordered workqueue\n");
+		return -ENOMEM;
+	}
+
 	return class_register(&leds_class);
 }
 
 static void __exit leds_exit(void)
 {
 	class_unregister(&leds_class);
+	destroy_workqueue(leds_wq);
 }
 
 subsys_initcall(leds_init);
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index 89c9806cc97f..9769ac49be20 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -266,7 +266,7 @@ void led_blink_set_nosleep(struct led_classdev *led_cdev, unsigned long delay_on
 		led_cdev->delayed_delay_on = delay_on;
 		led_cdev->delayed_delay_off = delay_off;
 		set_bit(LED_SET_BLINK, &led_cdev->work_flags);
-		schedule_work(&led_cdev->set_brightness_work);
+		queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
 		return;
 	}
 
@@ -297,7 +297,7 @@ void led_set_brightness(struct led_classdev *led_cdev, unsigned int brightness)
 		 */
 		if (!brightness) {
 			set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);
-			schedule_work(&led_cdev->set_brightness_work);
+			queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
 		} else {
 			set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
 				&led_cdev->work_flags);
@@ -333,7 +333,7 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value)
 		set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
 	}
 
-	schedule_work(&led_cdev->set_brightness_work);
+	queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
 }
 EXPORT_SYMBOL_GPL(led_set_brightness_nopm);
 
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 6300313c46b7..7c9f1cb12ab9 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -169,6 +169,7 @@ struct led_classdev {
 	int			 new_blink_brightness;
 	void			(*flash_resume)(struct led_classdev *led_cdev);
 
+	struct workqueue_struct *wq; /* LED workqueue */
 	struct work_struct	set_brightness_work;
 	int			delayed_set_value;
 	unsigned long		delayed_delay_on;
-- 
2.43.0

ATTENTION USERS/TESTERS: Re: [PATCH v1] leds: introduce ordered workqueue for leds events instead of system_wq

[Lee Jones]

INTENTIONAL TOP POST:

This is going to need more time on the list and hopefully draws the
attention of some potentially affected users / to-be testers.

> This allows to setup ordered workqueue for leds events. This may be
> useful, because default 'system_wq' does not guarantee execution order
> of each work_struct, thus for several brightness update requests (for
> multiple leds), real brightness switch could be in random order.
> 
> Yes, for sysfs-based leds we have flush_work() call inside
> brightness_store() operation, but it's blocking call, so userspace
> caller can be blocked at a long time, which means leds animation stream
> can be broken.
> 
> Ordered workqueue has the same behaviour as system_wq + flush_work(),
> but all scheduled works are async and userspace caller is not blocked,
> which it better for userspace animation scheduling.
> 
> Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
> Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
> ---
>  drivers/leds/led-class.c | 12 +++++++++++-
>  drivers/leds/led-core.c  |  6 +++---
>  include/linux/leds.h     |  1 +
>  3 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index ba1be15cfd8e..fba12471cf1f 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -25,6 +25,8 @@
>  static DEFINE_MUTEX(leds_lookup_lock);
>  static LIST_HEAD(leds_lookup_list);
>  
> +static struct workqueue_struct *leds_wq;
> +
>  static ssize_t brightness_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> @@ -57,7 +59,6 @@ static ssize_t brightness_store(struct device *dev,
>  	if (state == LED_OFF)
>  		led_trigger_remove(led_cdev);
>  	led_set_brightness(led_cdev, state);
> -	flush_work(&led_cdev->set_brightness_work);
>  
>  	ret = size;
>  unlock:
> @@ -549,6 +550,8 @@ int led_classdev_register_ext(struct device *parent,
>  
>  	led_update_brightness(led_cdev);
>  
> +	led_cdev->wq = leds_wq;
> +
>  	led_init_core(led_cdev);
>  
>  #ifdef CONFIG_LEDS_TRIGGERS
> @@ -667,12 +670,19 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
>  
>  static int __init leds_init(void)
>  {
> +	leds_wq = alloc_ordered_workqueue("leds", 0);
> +	if (!leds_wq) {
> +		pr_err("failed to create leds ordered workqueue\n");
> +		return -ENOMEM;
> +	}
> +
>  	return class_register(&leds_class);
>  }
>  
>  static void __exit leds_exit(void)
>  {
>  	class_unregister(&leds_class);
> +	destroy_workqueue(leds_wq);
>  }
>  
>  subsys_initcall(leds_init);
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 89c9806cc97f..9769ac49be20 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -266,7 +266,7 @@ void led_blink_set_nosleep(struct led_classdev *led_cdev, unsigned long delay_on
>  		led_cdev->delayed_delay_on = delay_on;
>  		led_cdev->delayed_delay_off = delay_off;
>  		set_bit(LED_SET_BLINK, &led_cdev->work_flags);
> -		schedule_work(&led_cdev->set_brightness_work);
> +		queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
>  		return;
>  	}
>  
> @@ -297,7 +297,7 @@ void led_set_brightness(struct led_classdev *led_cdev, unsigned int brightness)
>  		 */
>  		if (!brightness) {
>  			set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);
> -			schedule_work(&led_cdev->set_brightness_work);
> +			queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
>  		} else {
>  			set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
>  				&led_cdev->work_flags);
> @@ -333,7 +333,7 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value)
>  		set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
>  	}
>  
> -	schedule_work(&led_cdev->set_brightness_work);
> +	queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
>  }
>  EXPORT_SYMBOL_GPL(led_set_brightness_nopm);
>  
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 6300313c46b7..7c9f1cb12ab9 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -169,6 +169,7 @@ struct led_classdev {
>  	int			 new_blink_brightness;
>  	void			(*flash_resume)(struct led_classdev *led_cdev);
>  
> +	struct workqueue_struct *wq; /* LED workqueue */
>  	struct work_struct	set_brightness_work;
>  	int			delayed_set_value;
>  	unsigned long		delayed_delay_on;
> -- 
> 2.43.0
> 
> 

-- 
Lee Jones [李琼斯]

Re: ATTENTION USERS/TESTERS: Re: [PATCH v1] leds: introduce ordered workqueue for leds events instead of system_wq

[Lee Jones]

On Thu, 22 Aug 2024, Lee Jones wrote:

> INTENTIONAL TOP POST:
> 
> This is going to need more time on the list and hopefully draws the
> attention of some potentially affected users / to-be testers.

Another call for users to test this before I review/apply it.

Plan is to rotate it in to -next just after -rc1 has been released.

That should give it quite a few weeks in -next for people to test.

> > This allows to setup ordered workqueue for leds events. This may be
> > useful, because default 'system_wq' does not guarantee execution order
> > of each work_struct, thus for several brightness update requests (for
> > multiple leds), real brightness switch could be in random order.
> > 
> > Yes, for sysfs-based leds we have flush_work() call inside
> > brightness_store() operation, but it's blocking call, so userspace
> > caller can be blocked at a long time, which means leds animation stream
> > can be broken.
> > 
> > Ordered workqueue has the same behaviour as system_wq + flush_work(),
> > but all scheduled works are async and userspace caller is not blocked,
> > which it better for userspace animation scheduling.
> > 
> > Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
> > Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
> > ---
> >  drivers/leds/led-class.c | 12 +++++++++++-
> >  drivers/leds/led-core.c  |  6 +++---
> >  include/linux/leds.h     |  1 +
> >  3 files changed, 15 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> > index ba1be15cfd8e..fba12471cf1f 100644
> > --- a/drivers/leds/led-class.c
> > +++ b/drivers/leds/led-class.c
> > @@ -25,6 +25,8 @@
> >  static DEFINE_MUTEX(leds_lookup_lock);
> >  static LIST_HEAD(leds_lookup_list);
> >  
> > +static struct workqueue_struct *leds_wq;
> > +
> >  static ssize_t brightness_show(struct device *dev,
> >  		struct device_attribute *attr, char *buf)
> >  {
> > @@ -57,7 +59,6 @@ static ssize_t brightness_store(struct device *dev,
> >  	if (state == LED_OFF)
> >  		led_trigger_remove(led_cdev);
> >  	led_set_brightness(led_cdev, state);
> > -	flush_work(&led_cdev->set_brightness_work);
> >  
> >  	ret = size;
> >  unlock:
> > @@ -549,6 +550,8 @@ int led_classdev_register_ext(struct device *parent,
> >  
> >  	led_update_brightness(led_cdev);
> >  
> > +	led_cdev->wq = leds_wq;
> > +
> >  	led_init_core(led_cdev);
> >  
> >  #ifdef CONFIG_LEDS_TRIGGERS
> > @@ -667,12 +670,19 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
> >  
> >  static int __init leds_init(void)
> >  {
> > +	leds_wq = alloc_ordered_workqueue("leds", 0);
> > +	if (!leds_wq) {
> > +		pr_err("failed to create leds ordered workqueue\n");
> > +		return -ENOMEM;
> > +	}
> > +
> >  	return class_register(&leds_class);
> >  }
> >  
> >  static void __exit leds_exit(void)
> >  {
> >  	class_unregister(&leds_class);
> > +	destroy_workqueue(leds_wq);
> >  }
> >  
> >  subsys_initcall(leds_init);
> > diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> > index 89c9806cc97f..9769ac49be20 100644
> > --- a/drivers/leds/led-core.c
> > +++ b/drivers/leds/led-core.c
> > @@ -266,7 +266,7 @@ void led_blink_set_nosleep(struct led_classdev *led_cdev, unsigned long delay_on
> >  		led_cdev->delayed_delay_on = delay_on;
> >  		led_cdev->delayed_delay_off = delay_off;
> >  		set_bit(LED_SET_BLINK, &led_cdev->work_flags);
> > -		schedule_work(&led_cdev->set_brightness_work);
> > +		queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
> >  		return;
> >  	}
> >  
> > @@ -297,7 +297,7 @@ void led_set_brightness(struct led_classdev *led_cdev, unsigned int brightness)
> >  		 */
> >  		if (!brightness) {
> >  			set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);
> > -			schedule_work(&led_cdev->set_brightness_work);
> > +			queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
> >  		} else {
> >  			set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
> >  				&led_cdev->work_flags);
> > @@ -333,7 +333,7 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value)
> >  		set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
> >  	}
> >  
> > -	schedule_work(&led_cdev->set_brightness_work);
> > +	queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
> >  }
> >  EXPORT_SYMBOL_GPL(led_set_brightness_nopm);
> >  
> > diff --git a/include/linux/leds.h b/include/linux/leds.h
> > index 6300313c46b7..7c9f1cb12ab9 100644
> > --- a/include/linux/leds.h
> > +++ b/include/linux/leds.h
> > @@ -169,6 +169,7 @@ struct led_classdev {
> >  	int			 new_blink_brightness;
> >  	void			(*flash_resume)(struct led_classdev *led_cdev);
> >  
> > +	struct workqueue_struct *wq; /* LED workqueue */
> >  	struct work_struct	set_brightness_work;
> >  	int			delayed_set_value;
> >  	unsigned long		delayed_delay_on;
> > -- 
> > 2.43.0
> > 
> > 
> 
> -- 
> Lee Jones [李琼斯]

-- 
Lee Jones [李琼斯]

Re: [PATCH v1] leds: introduce ordered workqueue for leds events instead of system_wq

[Lee Jones]

On Tue, 20 Aug 2024, Dmitry Rokosov wrote:

> This allows to setup ordered workqueue for leds events. This may be
> useful, because default 'system_wq' does not guarantee execution order
> of each work_struct, thus for several brightness update requests (for
> multiple leds), real brightness switch could be in random order.
> 
> Yes, for sysfs-based leds we have flush_work() call inside
> brightness_store() operation, but it's blocking call, so userspace
> caller can be blocked at a long time, which means leds animation stream
> can be broken.
> 
> Ordered workqueue has the same behaviour as system_wq + flush_work(),
> but all scheduled works are async and userspace caller is not blocked,
> which it better for userspace animation scheduling.
> 
> Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
> Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
> ---
>  drivers/leds/led-class.c | 12 +++++++++++-
>  drivers/leds/led-core.c  |  6 +++---
>  include/linux/leds.h     |  1 +
>  3 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index ba1be15cfd8e..fba12471cf1f 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -25,6 +25,8 @@
>  static DEFINE_MUTEX(leds_lookup_lock);
>  static LIST_HEAD(leds_lookup_list);
>  
> +static struct workqueue_struct *leds_wq;

Does this _have_ to be global?

Isn't there a suitable data structure that we can store it in?

>  static ssize_t brightness_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> @@ -57,7 +59,6 @@ static ssize_t brightness_store(struct device *dev,
>  	if (state == LED_OFF)
>  		led_trigger_remove(led_cdev);
>  	led_set_brightness(led_cdev, state);
> -	flush_work(&led_cdev->set_brightness_work);
>  
>  	ret = size;
>  unlock:
> @@ -549,6 +550,8 @@ int led_classdev_register_ext(struct device *parent,
>  
>  	led_update_brightness(led_cdev);
>  
> +	led_cdev->wq = leds_wq;
> +
>  	led_init_core(led_cdev);
>  
>  #ifdef CONFIG_LEDS_TRIGGERS
> @@ -667,12 +670,19 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
>  
>  static int __init leds_init(void)
>  {
> +	leds_wq = alloc_ordered_workqueue("leds", 0);
> +	if (!leds_wq) {
> +		pr_err("failed to create leds ordered workqueue\n");

Nit: "LEDs"

> +		return -ENOMEM;
> +	}
> +
>  	return class_register(&leds_class);
>  }
>  
>  static void __exit leds_exit(void)
>  {
>  	class_unregister(&leds_class);
> +	destroy_workqueue(leds_wq);
>  }
>  
>  subsys_initcall(leds_init);
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 89c9806cc97f..9769ac49be20 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -266,7 +266,7 @@ void led_blink_set_nosleep(struct led_classdev *led_cdev, unsigned long delay_on
>  		led_cdev->delayed_delay_on = delay_on;
>  		led_cdev->delayed_delay_off = delay_off;
>  		set_bit(LED_SET_BLINK, &led_cdev->work_flags);
> -		schedule_work(&led_cdev->set_brightness_work);
> +		queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
>  		return;
>  	}
>  
> @@ -297,7 +297,7 @@ void led_set_brightness(struct led_classdev *led_cdev, unsigned int brightness)
>  		 */
>  		if (!brightness) {
>  			set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);
> -			schedule_work(&led_cdev->set_brightness_work);
> +			queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
>  		} else {
>  			set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
>  				&led_cdev->work_flags);
> @@ -333,7 +333,7 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value)
>  		set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
>  	}
>  
> -	schedule_work(&led_cdev->set_brightness_work);
> +	queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
>  }
>  EXPORT_SYMBOL_GPL(led_set_brightness_nopm);
>  
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 6300313c46b7..7c9f1cb12ab9 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -169,6 +169,7 @@ struct led_classdev {
>  	int			 new_blink_brightness;
>  	void			(*flash_resume)(struct led_classdev *led_cdev);
>  
> +	struct workqueue_struct *wq; /* LED workqueue */
>  	struct work_struct	set_brightness_work;
>  	int			delayed_set_value;
>  	unsigned long		delayed_delay_on;
> -- 
> 2.43.0
> 
> 

-- 
Lee Jones [李琼斯]

Re: [PATCH v1] leds: introduce ordered workqueue for leds events instead of system_wq

[Dmitry Rokosov]

On Tue, Sep 03, 2024 at 03:01:19PM +0100, Lee Jones wrote:
> On Tue, 20 Aug 2024, Dmitry Rokosov wrote:
> 
> > This allows to setup ordered workqueue for leds events. This may be
> > useful, because default 'system_wq' does not guarantee execution order
> > of each work_struct, thus for several brightness update requests (for
> > multiple leds), real brightness switch could be in random order.
> > 
> > Yes, for sysfs-based leds we have flush_work() call inside
> > brightness_store() operation, but it's blocking call, so userspace
> > caller can be blocked at a long time, which means leds animation stream
> > can be broken.
> > 
> > Ordered workqueue has the same behaviour as system_wq + flush_work(),
> > but all scheduled works are async and userspace caller is not blocked,
> > which it better for userspace animation scheduling.
> > 
> > Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
> > Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
> > ---
> >  drivers/leds/led-class.c | 12 +++++++++++-
> >  drivers/leds/led-core.c  |  6 +++---
> >  include/linux/leds.h     |  1 +
> >  3 files changed, 15 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> > index ba1be15cfd8e..fba12471cf1f 100644
> > --- a/drivers/leds/led-class.c
> > +++ b/drivers/leds/led-class.c
> > @@ -25,6 +25,8 @@
> >  static DEFINE_MUTEX(leds_lookup_lock);
> >  static LIST_HEAD(leds_lookup_list);
> >  
> > +static struct workqueue_struct *leds_wq;
> 
> Does this _have_ to be global?
> 

Unfortunately, yes, it has. Each LED described in the DTS, for example,
is represented as led_cdev. We do not have a led_device or a similar
structure to represent the entire LED device (the controller that
integrates all LEDs and manages them).

One option is to move leds_wq to the driver’s private data. However,
from my perspective, this is a more complicated solution, especially
considering that we have the ability to create a global leds_wq variable
in the core implementation, which can resolve the described issue
entirely.

> Isn't there a suitable data structure that we can store it in?
> 

> >  static ssize_t brightness_show(struct device *dev,
> >  		struct device_attribute *attr, char *buf)
> >  {
> > @@ -57,7 +59,6 @@ static ssize_t brightness_store(struct device *dev,
> >  	if (state == LED_OFF)
> >  		led_trigger_remove(led_cdev);
> >  	led_set_brightness(led_cdev, state);
> > -	flush_work(&led_cdev->set_brightness_work);
> >  
> >  	ret = size;
> >  unlock:
> > @@ -549,6 +550,8 @@ int led_classdev_register_ext(struct device *parent,
> >  
> >  	led_update_brightness(led_cdev);
> >  
> > +	led_cdev->wq = leds_wq;
> > +
> >  	led_init_core(led_cdev);
> >  
> >  #ifdef CONFIG_LEDS_TRIGGERS
> > @@ -667,12 +670,19 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
> >  
> >  static int __init leds_init(void)
> >  {
> > +	leds_wq = alloc_ordered_workqueue("leds", 0);
> > +	if (!leds_wq) {
> > +		pr_err("failed to create leds ordered workqueue\n");
> 
> Nit: "LEDs"
> 

Okay, I will send v2 patch today with fixed this line.

> > +		return -ENOMEM;
> > +	}
> > +
> >  	return class_register(&leds_class);
> >  }
> >  
> >  static void __exit leds_exit(void)
> >  {
> >  	class_unregister(&leds_class);
> > +	destroy_workqueue(leds_wq);
> >  }
> >  
> >  subsys_initcall(leds_init);
> > diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> > index 89c9806cc97f..9769ac49be20 100644
> > --- a/drivers/leds/led-core.c
> > +++ b/drivers/leds/led-core.c
> > @@ -266,7 +266,7 @@ void led_blink_set_nosleep(struct led_classdev *led_cdev, unsigned long delay_on
> >  		led_cdev->delayed_delay_on = delay_on;
> >  		led_cdev->delayed_delay_off = delay_off;
> >  		set_bit(LED_SET_BLINK, &led_cdev->work_flags);
> > -		schedule_work(&led_cdev->set_brightness_work);
> > +		queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
> >  		return;
> >  	}
> >  
> > @@ -297,7 +297,7 @@ void led_set_brightness(struct led_classdev *led_cdev, unsigned int brightness)
> >  		 */
> >  		if (!brightness) {
> >  			set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);
> > -			schedule_work(&led_cdev->set_brightness_work);
> > +			queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
> >  		} else {
> >  			set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
> >  				&led_cdev->work_flags);
> > @@ -333,7 +333,7 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value)
> >  		set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
> >  	}
> >  
> > -	schedule_work(&led_cdev->set_brightness_work);
> > +	queue_work(led_cdev->wq, &led_cdev->set_brightness_work);
> >  }
> >  EXPORT_SYMBOL_GPL(led_set_brightness_nopm);
> >  
> > diff --git a/include/linux/leds.h b/include/linux/leds.h
> > index 6300313c46b7..7c9f1cb12ab9 100644
> > --- a/include/linux/leds.h
> > +++ b/include/linux/leds.h
> > @@ -169,6 +169,7 @@ struct led_classdev {
> >  	int			 new_blink_brightness;
> >  	void			(*flash_resume)(struct led_classdev *led_cdev);
> >  
> > +	struct workqueue_struct *wq; /* LED workqueue */
> >  	struct work_struct	set_brightness_work;
> >  	int			delayed_set_value;
> >  	unsigned long		delayed_delay_on;
> > -- 
> > 2.43.0
> > 
> > 
> 
> -- 
> Lee Jones [李琼斯]

-- 
Thank you,
Dmitry