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leds: avoid races with workqueue

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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>
This commit is contained in:
Pavel Machek 2019-04-29 17:22:59 +02:00 committed by Jacek Anaszewski
parent 05b8ccfba5
commit 0db37915d9
2 changed files with 6 additions and 0 deletions
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1
drivers/leds/led-class.c
View File

@ -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:

5
drivers/leds/led-core.c
View File

@ -164,6 +164,11 @@ 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))