On Thu, 2010-06-10 at 21:53 +0200, Daniel Lezcano wrote:
> > + if (setpgid(handler->pid, 0)) {
> > + SYSERROR("failed to create new process group");
> > + goto out_delete_net;
> > + }
> > + DEBUG("created new process group %d", handler->pid);
> > + ctty = open("/dev/tty", O_RDONLY);
> > + if (ctty != -1) {
> > + int ret = tcsetpgrp(ctty, handler->pid);
> > + close(ctty);
> > + if (ret) {
> > + SYSERROR("failed to set terminal foreground
> process group");
> > + goto out_delete_net;
> > + }
> > + DEBUG("set terminal foreground process group");
> > + }
> >
>
> Is there a particular reason to do that from the parent and not from
> the
> child ?
>
Yes, because otherwise the new process group creation would be racy from
the parent POV. It's important because there's a window between the call
to setpgid() and the call to tcsetpgrp() where the child won't receive
tty signals, for example: it's up to the parent to forward signals to
the new process group in this case.
Usually, both the parent and the child call setpgid() to ensure they
have a consistent view, without the need to be synchronized.
--
Gregory Kurz gk...@fr.ibm.com
Software Engineer @ IBM/Meiosys http://www.ibm.com
Tel +33 (0)534 638 479 Fax +33 (0)561 400 420
"Anarchy is about taking complete responsibility for yourself."
Alan Moore.
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