Commit 0db37915 authored Apr 29, 2019 by Pavel Machek Committed by Jacek Anaszewski May 02, 2019

leds: avoid races with workqueue



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: 1afcadfc ("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>

parent 05b8ccfb

drivers/leds/led-class.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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:

drivers/leds/led-core.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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))