kern_setitimer
error = kern_setitimer(td, uap->which, itvp, &oitv);
error = kern_setitimer(td, ITIMER_REAL, &it, &old_it);
error = kern_setitimer(td, uap->which, &aitv, &oitv);
error = kern_setitimer(td, uap->which, &aitv, &oitv);
int kern_setitimer(struct thread *, u_int, struct itimerval *,