Hi! > >There are races between "main" thread and workqueue. They manifest > >themselves on Thinkpad X60: > >This should result in LED blinking, but it turns it off instead: > > root@amd:/data/pavel# cd /sys/class/leds/tpacpi\:\:power > > root@amd:/sys/class/leds/tpacpi::power# echo timer > trigger > > root@amd:/sys/class/leds/tpacpi::power# echo timer > trigger > > root@amd:/sys/class/leds/tpacpi::power# > >It should be possible to transition from blinking to solid on by echo > >0 > brightness; echo 1 > brightness... but that does not work, either, > >if done too quickly. > >Synchronization of the workqueue fixes both. > >Signed-off-by: Pavel Machek <pa...@ucw.cz> > > > >diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c > >index 68aa923..dcb59c8 100644 > >--- a/drivers/leds/led-class.c > >+++ b/drivers/leds/led-class.c > >@@ -57,6 +57,7 @@ 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); > > Is this really required here? It creates non-uniform brightness > setting behavior depending on whether it is set from sysfs or > by in-kernel call to led_set_brightness().
This fixes the echo 0 > brightness; echo 1 > brightness. It has to be
at a place where we can sleep.
If you have better idea, it is welcome, but it would be good to fix
the bug.
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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