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: 1afcadfcd1
("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>
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@ -57,6 +57,7 @@ static ssize_t brightness_store(struct device *dev,
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if (state == LED_OFF)
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led_trigger_remove(led_cdev);
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led_set_brightness(led_cdev, state);
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flush_work(&led_cdev->set_brightness_work);
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ret = size;
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unlock:
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@ -164,6 +164,11 @@ static void led_blink_setup(struct led_classdev *led_cdev,
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unsigned long *delay_on,
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unsigned long *delay_off)
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{
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/*
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* If "set brightness to 0" is pending in workqueue, we don't
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* want that to be reordered after blink_set()
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*/
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flush_work(&led_cdev->set_brightness_work);
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if (!test_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags) &&
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led_cdev->blink_set &&
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!led_cdev->blink_set(led_cdev, delay_on, delay_off))
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