SF_DETACHPENDING
if (sd->s_flags & SF_DETACHPENDING) {
sd->s_flags |= SF_DETACHPENDING;
if (!(sd->s_flags & SF_DETACHPENDING)) {
sd->s_flags &= ~SF_DETACHPENDING;
if (!(sd->s_flags & SF_DETACHPENDING)) {
sd->s_flags &= ~SF_DETACHPENDING;