Re: [PATCH] leds: core: Fix race condition for software blink

[Lee Jones <lee@kernel.org>]

On Fri, 08 May 2026, Craig McQueen wrote:

> Lee Jones wrote
>  > On Thu, 23 Apr 2026, Craig McQueen wrote: 
>  >  
>  > > led_set_brightness() function: Change handling of software blink to 
>  > > avoid race conditions when stopping blink and setting brightness. 
>  > > 
>  > > Triggers may call led_set_brightness(LED_OFF), 
>  > > led_set_brightness(LED_FULL) in quick succession to disable blinking and 
>  > > turn the LED on. If the delayed work task has not yet disabled blinking 
>  > > by the time the second call occurs, then the brightness also needs to be 
>  > > changed in the delayed work task. 
>  > > 
>  > > Signed-off-by: Craig McQueen <craig@mcqueen.au> 
>  > > --- 
>  > >  drivers/leds/led-core.c | 33 ++++++++++++++++++++------------- 
>  > >  1 file changed, 20 insertions(+), 13 deletions(-) 
>  >  
>  > I think this needs more eyes on it and to be thoroughly tested by others. 
> 
> The problem I have seen is when a Linux driver controls a trigger to change it from flashing to steady-on. I've seen it specifically with LED core's software blinking.
> 
> /* First stop the blinking */
> led_trigger_event(&udev->led_trigger, LED_OFF);
> /* Next turn the LED steady-on */
> led_trigger_event(&udev->led_trigger, LED_FULL);
> 
> Without this patch, the LED usually ends up in the off state, rather than on.
> 
> I have tested this patch on a Rockchip RK3328 based system (ARM 64).

I'm sure that this patch does work for you.  Just as the last iteration
of this function has been working fine for everyone else for the last 10
years.  However, since this is core change, I shall be exercising
caution.

If anyone would be kind enough to test it, or provide some extra eyes,
I'd be appreciative.

-- 
Lee Jones