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leds: Fix set_brightness_delayed() race

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When a trigger wants to switch from blinking to LED on it needs to call:
	led_set_brightness(LED_OFF);
	led_set_brightness(LED_FULL);

To first call disables blinking and the second then turns the LED on
(the power-supply charging-blink-full-solid triggers do this).

These calls happen immediately after each other, so it is possible
that set_brightness_delayed() from the first call has not run yet
when the led_set_brightness(LED_FULL) call finishes.

If this race hits then this is causing problems for both
sw- and hw-blinking:

For sw-blinking set_brightness_delayed() clears delayed_set_value
when LED_BLINK_DISABLE is set causing the led_set_brightness(LED_FULL)
call effects to get lost when hitting the race, resulting in the LED
turning off instead of on.

For hw-blinking if the race hits delayed_set_value has been
set to LED_FULL by the time set_brightness_delayed() runs.
So led_cdev->brightness_set_blocking() is never called with
LED_OFF as argument and the hw-blinking is never disabled leaving
the LED blinking instead of on.

Fix both issues by adding LED_SET_BRIGHTNESS and LED_SET_BRIGHTNESS_OFF
work_flags making this 2 separate actions to be run by
set_brightness_delayed().

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Tested-by: Yauhen Kharuzhy <jekhor@gmail.com>
Link: https://lore.kernel.org/r/20230510162234.291439-3-hdegoede@redhat.com
Signed-off-by: Lee Jones <lee@kernel.org>
This commit is contained in:
Hans de Goede 2023-05-10 18:22:32 +02:00 committed by Lee Jones
parent e298d8a38b
commit fa15d8c692
2 changed files with 47 additions and 13 deletions
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57
drivers/leds/led-core.c
View file

@ -114,21 +114,14 @@ static void led_timer_function(struct timer_list *t)
mod_timer(&led_cdev->blink_timer, jiffies + msecs_to_jiffies(delay));
}
static void set_brightness_delayed(struct work_struct *ws)
static void set_brightness_delayed_set_brightness(struct led_classdev *led_cdev,
unsigned int value)
{
struct led_classdev *led_cdev =
container_of(ws, struct led_classdev, set_brightness_work);
int ret = 0;
if (test_and_clear_bit(LED_BLINK_DISABLE, &led_cdev->work_flags)) {
led_cdev->delayed_set_value = LED_OFF;
led_stop_software_blink(led_cdev);
}
ret = __led_set_brightness(led_cdev, led_cdev->delayed_set_value);
ret = __led_set_brightness(led_cdev, value);
if (ret == -ENOTSUPP)
ret = __led_set_brightness_blocking(led_cdev,
led_cdev->delayed_set_value);
ret = __led_set_brightness_blocking(led_cdev, value);
if (ret < 0 &&
/* LED HW might have been unplugged, therefore don't warn */
!(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
@ -137,6 +130,30 @@ static void set_brightness_delayed(struct work_struct *ws)
"Setting an LED's brightness failed (%d)\n", ret);
}
static void set_brightness_delayed(struct work_struct *ws)
{
struct led_classdev *led_cdev =
container_of(ws, struct led_classdev, set_brightness_work);
if (test_and_clear_bit(LED_BLINK_DISABLE, &led_cdev->work_flags)) {
led_stop_software_blink(led_cdev);
set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
}
/*
* Triggers may call led_set_brightness(LED_OFF),
* led_set_brightness(LED_FULL) in quick succession to disable blinking
* and turn the LED on. Both actions may have been scheduled to run
* before this work item runs once. To make sure this works properly
* handle LED_SET_BRIGHTNESS_OFF first.
*/
if (test_and_clear_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags))
set_brightness_delayed_set_brightness(led_cdev, LED_OFF);
if (test_and_clear_bit(LED_SET_BRIGHTNESS, &led_cdev->work_flags))
set_brightness_delayed_set_brightness(led_cdev, led_cdev->delayed_set_value);
}
static void led_set_software_blink(struct led_classdev *led_cdev,
unsigned long delay_on,
unsigned long delay_off)
@ -271,8 +288,22 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value)
if (!__led_set_brightness(led_cdev, value))
return;
/* If brightness setting can sleep, delegate it to a work queue task */
led_cdev->delayed_set_value = value;
/*
* Brightness setting can sleep, delegate it to a work queue task.
* value 0 / LED_OFF is special, since it also disables hw-blinking
* (sw-blink disable is handled in led_set_brightness()).
* To avoid a hw-blink-disable getting lost when a second brightness
* change is done immediately afterwards (before the work runs),
* it uses a separate work_flag.
*/
if (value) {
led_cdev->delayed_set_value = value;
set_bit(LED_SET_BRIGHTNESS, &led_cdev->work_flags);
} else {
clear_bit(LED_SET_BRIGHTNESS, &led_cdev->work_flags);
set_bit(LED_SET_BRIGHTNESS_OFF, &led_cdev->work_flags);
}
schedule_work(&led_cdev->set_brightness_work);
}
EXPORT_SYMBOL_GPL(led_set_brightness_nopm);

3
include/linux/leds.h
View file

@ -124,6 +124,9 @@ struct led_classdev {
#define LED_BLINK_INVERT 3
#define LED_BLINK_BRIGHTNESS_CHANGE 4
#define LED_BLINK_DISABLE 5
/* Brightness off also disables hw-blinking so it is a separate action */
#define LED_SET_BRIGHTNESS_OFF 6
#define LED_SET_BRIGHTNESS 7
/* Set LED brightness level
* Must not sleep. Use brightness_set_blocking for drivers