LDEV_SI_DTR
MPASS((ldev->siref & LDEV_SI_DTR) == 0);
atomic_set_int(&ldev->siref, LDEV_SI_DTR);
while ((atomic_load_int(&ldev->siref) & ~LDEV_SI_DTR) != 0)
if ((siref & LDEV_SI_DTR) != 0) {
MPASS((ldev->siref & LDEV_SI_DTR) == 0);
MPASS((ldev->siref & ~LDEV_SI_DTR) != 0);