sigev_findtd
if (sigev_findtd(p, &it->it_sigev, &td) != 0) {
error = sigev_findtd(p, &nt->nt_sigev, &td);
error = sigev_findtd(p, sigev, &td);
int sigev_findtd(struct proc *p, struct sigevent *sigev, struct thread **);