From: Pavel Machek pavel@ucw.cz
[ Upstream commit 0db37915d912e8dc6588f25da76d3ed36718d92f ]
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
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.
Fixes: 1afcadfcd184 ("leds: core: Use set_brightness_work for the blocking op") Signed-off-by: Pavel Machek pavel@ucw.cz Signed-off-by: Jacek Anaszewski jacek.anaszewski@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/leds/led-class.c | 1 + drivers/leds/led-core.c | 5 +++++ 2 files changed, 6 insertions(+)
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c index b0e2d55acbd6f..80374c6c943ad 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);
ret = size; unlock: diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c index 9ce6b32f52a19..cb84c35d64f97 100644 --- a/drivers/leds/led-core.c +++ b/drivers/leds/led-core.c @@ -162,6 +162,11 @@ static void led_blink_setup(struct led_classdev *led_cdev, unsigned long *delay_on, unsigned long *delay_off) { + /* + * 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); if (!test_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags) && led_cdev->blink_set && !led_cdev->blink_set(led_cdev, delay_on, delay_off))