IQS_BUSY
iq->state = IQS_BUSY;
state = atomic_cas_uint(&iq->state, IQS_IDLE, IQS_BUSY);
(void) atomic_cas_uint(&iq->state, IQS_BUSY, IQS_IDLE);
IQS_BUSY) == IQS_IDLE) {
&q->state, IQS_BUSY,
(void) atomic_cas_uint(&q->state, IQS_BUSY, IQS_IDLE);