WFLAG_ACTIVE
if ((npf->worker_flags & WFLAG_ACTIVE) == 0) {
npf->worker_flags |= WFLAG_ACTIVE;
if ((npf->worker_flags & WFLAG_ACTIVE) == 0) {
KASSERT(npf->worker_flags & WFLAG_ACTIVE);
while (npf->worker_flags & WFLAG_ACTIVE) {
KASSERT(npf->worker_flags & WFLAG_ACTIVE);