The race fixed in timer_trig_activate() between a blocking set_brightness() call and trigger->activate() can affect any trigger. So move the call to flush_work() into led_trigger_set() where it can avoid the race for all triggers.

Fixes: 0db37915d912 ("leds: avoid races with workqueue") Fixes: 8c0f693c6eff ("leds: avoid flush_work in atomic context") Cc: stable@vger.kernel.org Tested-by: Dustin L. Howett dustin@howett.net Signed-off-by: Thomas Weißschuh linux@weissschuh.net --- Changes in v2: - Cc stable - Add Dustin's Tested-by - Rebase against led/for-leds-next - Always execute flush_work(), similar to synchronize_rcu() - Link to v1: https://lore.kernel.org/r/20240603-led-trigger-flush-v1-1-c904c6e2fb34@weiss... ---

Commit 7abae7a11fc9 ("leds: trigger: Call synchronize_rcu() before calling trig->activate()") alone also solves the issue that the LED stays completely off after enabling the trigger. But there is a recognizable timeframe where it is disabled in between.

Also from a correctness perspective, this seems like a coincidence and the call to flush_work() is the correct fix for that race. --- drivers/leds/led-triggers.c | 6 ++++++ drivers/leds/trigger/ledtrig-timer.c | 5 ----- 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c index 59deadb86335..78eb20093b2c 100644 --- a/drivers/leds/led-triggers.c +++ b/drivers/leds/led-triggers.c @@ -201,6 +201,12 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig) */ synchronize_rcu();

+ /* + * If "set brightness to 0" is pending in workqueue, + * we don't want that to be reordered after ->activate() + */ + flush_work(&led_cdev->set_brightness_work); + ret = 0; if (trig->activate) ret = trig->activate(led_cdev); diff --git a/drivers/leds/trigger/ledtrig-timer.c b/drivers/leds/trigger/ledtrig-timer.c index b4688d1d9d2b..1d213c999d40 100644 --- a/drivers/leds/trigger/ledtrig-timer.c +++ b/drivers/leds/trigger/ledtrig-timer.c @@ -110,11 +110,6 @@ static int timer_trig_activate(struct led_classdev *led_cdev) led_cdev->flags &= ~LED_INIT_DEFAULT_TRIGGER; }

- /* - * 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); led_blink_set(led_cdev, &led_cdev->blink_delay_on, &led_cdev->blink_delay_off);

--- base-commit: 005408af25d5550e1bd22a18bf371651969c17ee change-id: 20240603-led-trigger-flush-3bef303eb902

Best regards,