ACPISEM_AVAIL
if (!ACPISEM_AVAIL(as, Units))
while (!ACPISEM_AVAIL(as, Units)) {
while (!ACPISEM_AVAIL(as, Units)) {
while (!ACPISEM_AVAIL(as, Units)) {
if (ACPISEM_AVAIL(as, Units))
if (as->as_waiters > 0 && ACPISEM_AVAIL(as, Units))