leds: triggers: Flush pending brightness before activating trigger

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: [e-mail]
Tested-by: Dustin L. Howett <[e-mail]>
Signed-off-by: Thomas Weißschuh <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/leds/led-triggers.c

···
 		 */
 		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);

drivers/leds/trigger/ledtrig-timer.c

···
 		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);