On Mon, Dec 26, 2005 at 11:27:44PM -0800, Matthew Dillon wrote:
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> I think it's the same issue. The ^Z effects all processes in
> the process group. waitpid in the parent tries to return the
> stopped state of the child, but the parent itself is stopped
> and the status is not returned until you 'fg'. This starts
> both parent and child, but then the parent processes the
> return from the waitpid and stops itself again.
Ok, the code doesn't really reflect my question here; on computers here
running other OSes, including DragonFly 1.2.x-RELEASE, waitpid() (or wait4)
doesn't return after ^Z+`fg' even with WUNTRACED (I can confirm this by the
fact that warnx() doesn't print "WSTOPSIG(%d) = %d\n" message), thus no such
problem exists. I don't know if it's an (POSIX-ly or SUS-ly?) expected
behavior, but are we going to change that?
> : for (;;) {
> : caught = waitpid(pid, &st, WUNTRACED);
> : warnx("waitpid returned %d\n", caught);
> : errno = WEXITSTATUS(st);
> : if (caught == -1)
> : return 1;
> : else if (WIFSTOPPED(st)) {
> : sig = WSTOPSIG(st);
> : warnx("WSTOPSIG(%d) = %d\n", st, sig);
> : sig = SIGSTOP;
> : raise(sig);
> : warnx("after raise(%d)\n", sig);
> : }
