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Message-ID: <20241029200632.chysrb7teyc7dsrq@CAB-WSD-L081021>
Date: Tue, 29 Oct 2024 23:06:59 +0300
From: Dmitry Rokosov <ddrokosov@...utedevices.com>
To: Lee Jones <lee@...nel.org>
CC: <pavel@....cz>, <linux-kernel@...r.kernel.org>,
<linux-leds@...r.kernel.org>, <kernel@...utedevices.com>,
<rockosov@...il.com>, Alexey Romanov <avromanov@...utedevices.com>
Subject: Re: [PATCH v2] leds: introduce ordered workqueue for leds events
instead of system_wq
Hello Lee,
Kindly reminder.
On Tue, Oct 22, 2024 at 05:22:48PM +0300, Dmitry Rokosov wrote:
> Hello Lee,
>
> I hope this message finds you well.
> I wanted to ask for your thoughts on whether there was enough time for
> testing and if we can proceed with merging this patchset.
>
> I appreciate any feedback about it.
>
> On Tue, Sep 17, 2024 at 09:04:12AM +0100, Lee Jones wrote:
> > On Mon, 16 Sep 2024, Dmitry Rokosov wrote:
> >
> > > Hello Lee!
> > >
> > > What are the next steps? Should I make any changes, or are we waiting
> > > for test results from the mailing list members?
> >
> > This is an intrusive core change that was submitted during -rc6.
> >
> > It's going to need some time on the list for people to respond.
> >
> > > Sorry for the ping.
> > >
> > > On Wed, Sep 04, 2024 at 01:39:30AM +0300, 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@...utedevices.com>
> > > > Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
> > > > ---
> > > > Changes v2 since v1 at [1]:
> > > > - replace "leds" with "LEDs" in the log message
> > > >
> > > > Links:
> > > > [1] https://lore.kernel.org/all/20240820155407.32729-1-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 c66d1bead0a4..b5e28ad54f7f 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:
> > > > @@ -548,6 +549,8 @@ 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
> > > > @@ -666,12 +669,19 @@ 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
--
Thank you,
Dmitry
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