flush_workqueue_prep_pwqs
if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))