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SubjectRe: >256 ptys (previous subject line was garbage)
From
   Date: Tue, 9 Jun 1998 10:36:38 +1000
From: Richard Gooch <Richard.Gooch@atnf.CSIRO.AU>

Well, I've seen one comment already questioning whether major/minor
device locks are the better way of doing it, instead of flock(2).

flock(2) simply doesn't work because you may need to keep a tty locked
beyond the lifetime of the process which originally locked the tty.

However, ignoring that, I think it would be simple enough to implement
a non tty-specific locking scheme in devfs. I already have the auto
ownership facility.
What does this device locking need? Just limit the number of open(2)s
to 1?

tty locking really doesn't belong in the kernel. It's a lot more
complex than limiting the number of open's to 1. You need to worry
about people who have a blocking open waiting for carrier detect going
high; you need to worry with multiple processes opening /dev/tty when
someone is logged into a dialup modem. You need to worry about people
running xmodem in a separate process from kermit, etc., etc.

- Ted

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