Date: Sat, 6 Apr 1996 11:11:14 +0200 From: Thomas Roell <roell@blah.a.isar.de> To: hackers@FreeBSD.org, jkh@time.cdrom.com, roell@xinside.com Subject: Re: The F_SETOWN problem.. Message-ID: <199604060911.LAA00234@blah.a.isar.de> In-Reply-To: <29203.828776164@time.cdrom.com> References: <29203.828776164@time.cdrom.com>
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In your message of 5 April 1996 you write:
> Bruce's reply.. I've sent out another message asking whether or not
> we intend to actually make this work.. :-)
Ok, I'll take this up to general discussion.
> ------- Forwarded Message
>
> Replied: Fri, 05 Apr 1996 23:34:33 -0800
> Replied: "Bruce Evans <bde@zeta.org.au> hackers@FreeBSD.org"
> Return-Path: bde@zeta.org.au
> Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19]) by time.cdrom.com (8.7.5/8.6.9) with SMTP id XAA29003 for <jkh@time.cdrom.com>; Fri, 5 Apr 1996 23:21:57 -0800 (PST)
> Received: (from bde@localhost) by godzilla.zeta.org.au (8.6.12/8.6.9) id RAA14868; Sat, 6 Apr 1996 17:16:20 +1000
> Date: Sat, 6 Apr 1996 17:16:20 +1000
> From: Bruce Evans <bde@zeta.org.au>
> Message-Id: <199604060716.RAA14868@godzilla.zeta.org.au>
> To: hackers@FreeBSD.org, jkh@time.cdrom.com
> Subject: Re: Any clues as to why this fails?
>
> >#include <signal.h>
> >#include <fcntl.h>
>
> >void
> >handler(int sig)
> >{
> > printf("Signal %d received\n", sig);
> >}
>
> >main()
> >{
> > int i, fd;
>
> > signal(SIGIO, handler);
>
> > fd = open("/dev/cuaa1", O_RDONLY | O_NONBLOCK | O_EXCL);
> > printf("%d\n", fd);
> > i = fcntl(fd, F_GETFL, 0);
> > printf("%d\n", i);
> > printf("%d\n", fcntl(fd, F_SETFL, i | O_ASYNC));
> > printf("%d\n", fcntl(fd, F_SETOWN, getpid())); /* This call returns -1 */
> > pause();
> >}
>
> >I've read the man page for fcntl() and it really appears as though
> >that F_SETOWN call should work. Any clues as to why not? This
>
> F_SETOWN on a tty only works for controlling terminals. This is because
> F_SETOWN is implemented as tcsetpgrp() and tcsetpgrp() is specified by
> POSIX. To work like you want, F_SETOWN would need a separate pgrp
> entries in the tty struct. Sockets work like you want because there is
> no POSIX pgrp entry to conflict with. F_SETOWN doesn't work on anything
> except ttys, sockets or perhaps pipes. To work as documented in fcntl.3,
> F_SETOWN would need to have a pgrp entry in the filedesc struct. This
> would probably be useful - it would allow sending SIGIO to arbitrary
> sets of sufficiently privileged processes.
Ok, then I had 2 or 3 maybe very stupid sounding questions (and believe me,
I tried to work around them for quite a while now):
1) How do I get my process to be the controlling pgrp of this tty ? I
tried all things that worked under SVR4, but I'm lost on this one.
Just a couple of sample code lines would help me here incredible.
2) Can my progress have two controlling ttys ? Basically this process
is also going to open /dev/ttyv3 (as an example), reading the
keyboard and also wanting to recieve a SIGIO (which fails right now
the same way).
3) Since this process has opened already a virutal terminal, he is
recieving signals for VT switching. Now if I would detach this one
from being the controlling tty and move the controlling tty to
/dev/cuaa1, would I still get those signals ?
- Thomas
--
Denver Office THOMAS ROELL /\ Das Reh springt hoch,
+1(303)298-7478 X INSIDE INC / \/\ das Reh springt weit,
1801 Broadway, Suite 1710 / \ \/\ was soll es tun,
Denver, CO 80202 roell@xinside.com / Oelch! \ \ es hat ja Zeit.
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