DOOR_T_HELD
if (DOOR_T_HELD(ct))
else if (DOOR_T_HELD(st))
ASSERT(DOOR_T_HELD(ct) || ct->d_kernel);
ASSERT(DOOR_T_HELD(st));
ASSERT(DOOR_T_HELD(ct));
while (DOOR_T_HELD(ct))
while (DOOR_T_HELD(ct))
(ASSERT(!DOOR_T_HELD(cst)), ((cst)->d_hold = 1))
(ASSERT(DOOR_T_HELD(cst)), ((cst)->d_hold = 0), \