// unlockIfHeld will unlock a lock, if it is held by this machine, or return an error.
func unlockIfHeld(lck *lock.Lock) error {
	err := lck.Unlock()
	if err == lock.ErrNotExist {
		return nil
	} else if err == nil {
		fmt.Println("Unlocked existing lock for this machine")
		return nil
	}

	return err
}

// lockAndReboot attempts to acquire the lock and reboot the machine in an
// infinite loop. Returns if the reboot failed.
func (r rebooter) lockAndReboot(lck *lock.Lock) {
	interval := initialInterval
	for {
		err := lck.Lock()
		if err != nil && err != lock.ErrExist {
			interval = expBackoff(interval)
			fmt.Printf("Retrying in %v. Error locking: %v\n", interval, err)
			time.Sleep(interval)

			continue
		}

		rebootAndSleep(r.lgn)

		return
	}
}