rumpuser_cv_wait
void rumpuser_cv_wait(struct rumpuser_cv *, struct rumpuser_mtx *);
rumpuser_cv_wait(RUMPCV(cv), RUMPMTX(mtx));
rumpuser_cv_wait(RUMPCV(&p->p_waitcv),
rumpuser_cv_wait(lts.ucv, rump_giantlock);
rumpuser_cv_wait(cv, rcpu->rcpu_mtx);