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@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxxxxx>
> ---
> 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]
