fork1
if ((error = fork1(td, &fr)) != 0)
error = fork1(td, &fr);
if ((error = fork1(td, &fr)) != 0)
error = fork1(&thread0, &fr);
error = fork1(td, &fr);
error = fork1(td, &fr);
error = fork1(td, &fr);
error = fork1(td, &fr);
error = fork1(td, &fr);
error = fork1(&thread0, &fr);
int fork1(struct thread *, struct fork_req *);