2024-06-03 21:51:43

by Thomas Weißschuh

Subject: [PATCH] leds: triggers: flush pending brightness before activating trigger

The race fixed in timer_trig_activate() between a blocking
set_brightness() call and trigger->activate() can affect any trigger.
So move the call to flush_work() into led_trigger_set() where it can
avoid the race for all triggers.

Fixes: 0db37915d912 ("leds: avoid races with workqueue")
Fixes: 8c0f693c6eff ("leds: avoid flush_work in atomic context")
Signed-off-by: Thomas Weißschuh <[email protected]>
---
Dustin, could you validate that this fixes the issue you encountered in
the cros_ec led driver?
---
drivers/leds/led-triggers.c | 10 ++++++++--
drivers/leds/trigger/ledtrig-timer.c | 5 -----
2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index b1b323b19301..9e6233dbcfd4 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -195,10 +195,16 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
led_cdev->trigger = trig;

ret = 0;
- if (trig->activate)
+ if (trig->activate) {
+ /*
+ * If "set brightness to 0" is pending in workqueue,
+ * we don't want that to be reordered after ->activate()
+ */
+ flush_work(&led_cdev->set_brightness_work);
ret = trig->activate(led_cdev);
- else
+ } else {
led_set_brightness(led_cdev, trig->brightness);
+ }
if (ret)
goto err_activate;

diff --git a/drivers/leds/trigger/ledtrig-timer.c b/drivers/leds/trigger/ledtrig-timer.c
index b4688d1d9d2b..1d213c999d40 100644
--- a/drivers/leds/trigger/ledtrig-timer.c
+++ b/drivers/leds/trigger/ledtrig-timer.c
@@ -110,11 +110,6 @@ static int timer_trig_activate(struct led_classdev *led_cdev)
led_cdev->flags &= ~LED_INIT_DEFAULT_TRIGGER;
}

- /*
- * If "set brightness to 0" is pending in workqueue, we don't
- * want that to be reordered after blink_set()
- */
- flush_work(&led_cdev->set_brightness_work);
led_blink_set(led_cdev, &led_cdev->blink_delay_on,
&led_cdev->blink_delay_off);


---
base-commit: f06ce441457d4abc4d76be7acba26868a2d02b1c
change-id: 20240603-led-trigger-flush-3bef303eb902

Best regards,
--
Thomas Weißschuh <[email protected]>

2024-06-04 18:02:54

by Dustin Howett

Subject: Re: [PATCH] leds: triggers: flush pending brightness before activating trigger

On Mon, Jun 3, 2024 at 4:45 PM Thomas Weißschuh <[email protected]> wrote:
>
> Dustin, could you validate that this fixes the issue you encountered in
> the cros_ec led driver?

Thanks for the quick patch. Yes, it fixes the issue I encountered with
leds_cros_ec!

Tested-by: Dustin L. Howett <[email protected]>

Cheers,
d

2024-06-13 15:03:40

by Lee Jones

Subject: Re: [PATCH] leds: triggers: flush pending brightness before activating trigger

On Mon, 03 Jun 2024, Thomas Weißschuh wrote:

> The race fixed in timer_trig_activate() between a blocking
> set_brightness() call and trigger->activate() can affect any trigger.
> So move the call to flush_work() into led_trigger_set() where it can
> avoid the race for all triggers.
>
> Fixes: 0db37915d912 ("leds: avoid races with workqueue")
> Fixes: 8c0f693c6eff ("leds: avoid flush_work in atomic context")
> Signed-off-by: Thomas Weißschuh <[email protected]>
> ---
> Dustin, could you validate that this fixes the issue you encountered in
> the cros_ec led driver?
> ---
> drivers/leds/led-triggers.c | 10 ++++++++--
> drivers/leds/trigger/ledtrig-timer.c | 5 -----
> 2 files changed, 8 insertions(+), 7 deletions(-)

This patch clashes with:

https://lore.kernel.org/all/[email protected]/

Please rebase and ensure that your solution doesn't conflict.

--
Lee Jones [李琼斯]