need_to_create_worker
if (need_to_create_worker(pool)) {
if (create_worker(pool) || !need_to_create_worker(pool))
if (!need_to_create_worker(pool))
if (need_to_create_worker(pool))
if (!need_to_create_worker(pool)) {
pwq->nr_active && need_to_create_worker(pool)) {