From fa15d8c69238b352cc143cb9d8f2ca4594b94022 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Wed, 10 May 2023 18:22:32 +0200 Subject: leds: Fix set_brightness_delayed() race 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 Reviewed-by: Jacek Anaszewski Tested-by: Yauhen Kharuzhy Link: https://lore.kernel.org/r/20230510162234.291439-3-hdegoede@redhat.com Signed-off-by: Lee Jones --- drivers/leds/led-core.c | 57 ++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 44 insertions(+), 13 deletions(-) (limited to 'drivers') diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c index 4a97cb745788..e61acc785410 100644 --- a/drivers/leds/led-core.c +++ b/drivers/leds/led-core.c @@ -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); -- cgit v1.2.3