I don't see a race -- the article says: "Take no action when SIGINT is received while you wait for a child. You make a note of the fact that you did receive it,

I don't see a race -- the article says: "Take no action when SIGINT is received while you wait for a child. You make a note of the fact that you did receive it, though." Then, after waiting on the child, "Look at whether you (the shell) has received SIGINT while the child was in the foreground", and the shell kills itself with SIGINT if so.