IQS_BUSY
if (atomic_cmpset_int(&iq->state, IQS_IDLE, IQS_BUSY)) {
(void) atomic_cmpset_int(&iq->state, IQS_BUSY, IQS_IDLE);
if (atomic_cmpset_int(&iq->state, IQS_IDLE, IQS_BUSY)) {
(void) atomic_cmpset_int(&iq->state, IQS_BUSY, IQS_IDLE);
KASSERT(iq->state == IQS_BUSY, ("%s: iq %p not BUSY", __func__, iq));
IQS_BUSY)) {
IQS_BUSY, IQS_IDLE);
(void) atomic_cmpset_int(&q->state, IQS_BUSY, IQS_IDLE);
KASSERT(iq->state == IQS_BUSY, ("%s: iq %p not BUSY", __func__, iq));