Date: Thu, 14 Nov 1996 04:34:53 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, roell@crab.xinside.com Cc: hackers@freebsd.org, jkh@time.cdrom.com Subject: Re: Is our ASYNC I/O support for ttys broken? Message-ID: <199611131734.EAA11083@godzilla.zeta.org.au>
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>> The status hasn't changed since he complained a year or so ago.
>> SIGIO for ASYNC tty i/o is only sent to the process group of the tty,
>> and process group stuff is limited by it being POSIX conformant
>> with few extensions - the process group can not be changed using
>Would it be possible to change that behaviour in the future ?
Of course.
>> > fd = open("/dev/ttyd0", O_RDONLY | O_NONBLOCK);
>> >
>> > fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | FASYNC);
>> > fcntl(fd, F_SETOWN, getpid());
>>
>> The second fcntl is guaranteed to fail, since `fd' isn't a controlling
>> terminal. To make fd a controlling terminal, something like the following
>> must be done:
>>
>> fork()
>> wait in parent, continue as follows in child:
>> setsid(); /* become a session leader with no ctty */
>> open as above
>> first fcntl as above
>> ioctl(fd, TIOCSCTTY, NULL); /* make fd the ctty */
>> second fcntl as above
>
>Tried that already. Doesn't work.
It works with getpid() replaced by `-getpgrp()'.
>Problem is that I really don't want to spawn subprocesses for
>io-stuff. On the other hand asynchronous input is really mandatory if
>you have a heavily loaded box and run CDE and/or OpenGL/PEX apps.
Is this for the X server? It's already in the background and doesn't
have a controlling terminal (at least for XFree :-) so no additional
processes are required for handling one mouse.
Bruce
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