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Date: Fri, 7 Mar 1997 16:44:34 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199703070544.QAA02103@godzilla.zeta.org.au>
To: msmith@atrad.adelaide.edu.au, pius@ienet.com
Subject: Re: Linux JDK on 2.2
Cc: hackers@freebsd.org, mark@quickweb.com, sos@ravenock.cybercity.dk
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
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>In linux_file.c there's this comment in the linux_fcntl function:
>
>    case LINUX_F_SETOWN:
>    case LINUX_F_GETOWN:
>        /*
>         * We need to route around the normal fcntl() for these calls,
>         * since it uses TIOC{G,S}PGRP, which is too restrictive for
>         * Linux F_{G,S}ETOWN semantics. For sockets, this problem
>         * does not exist.
>         */
>
>So, how are FreeBSD's F_{G,S}ETOWN semantics different from Linux's?

FreeBSD's F_{G,S}ETOWN/O_ASYNC implementation is completely broken:
- it should apply to open file instances, but actually applies to
  devices.
- normal kill() permissions don't apply.  Any process can send SIGIO
  to any process using a socket.
- for ttys, the process group handling is tangled up with POSIX
  POSIX group handling.  The process group can only be set to that
  of a session leader with the tty as its controlling terminal.
  It is impossible to set the pgrp to a process instead of a group.
- there are some confusing double negatives to convert from negative
  pids to positive process group numbers and back.  ISTR that at least
  one driver gets this wrong.

Bruce