On 2/24/20 5:18 PM, Chet Ramey wrote:
The first case is trickier: there's always going to be a window between
the time the shell checks for pending traps and the time the wait builtin
starts to run. You can't really close it unless you're willing to run the
trap out of the signal handler, which everyone agrees is a bad idea, but
you can squeeze it down to practially nothing.
dash uses something along these lines:
sigfillset(&mask);
sigprocmask(SIG_SETMASK, &mask, &mask);
while (!pending_sig)
sigsuspend(&mask);
sigprocmask(SIG_SETMASK, &mask, NULL);
if (pending_sig)
handle_signals(pending_sig);
pid = waitpid(... WNOHANG);
It sleeps in sigsuspend(), not in waitpid(). This way we wait for both
signals *and* children (by virtue of getting SIGCHLD for them).
