Hangups about vhangup()

[Joe Kelsey]

vhangup() doesn't do ALL of what I want it to do.  What it DOES do
quite well is turn off I/O to the particular tty in question when
someone logs out with background processes still running.
Unfortunately, the background process still has the tty in question
open, so the various reference count fields associated with the
terminal never drop to zero, and if it happens to be set HUPCLS, the
tty close routine never gets called to actually hang up the line.  This
is a problem especially if you have your terminals connected to a port
selector (like a Micom 600), since the line won't be automatically
disconnected at logout.  I've been staring at kernel source all morning
and I can't really see any easy way to fix vhangup().  One possibility
would be to actually call closef() from within the inner loop of
forceclose(), but this might cause problems when the process in
question eventually issues its own close().  I can't really tell if it
WOULD cause a problem, although I suspect that there are a lot of race
conditions  possible.  If I could substitute a reference to /dev/null
somehow that would be the best, but I'm not sure exactly how I would do
all this from the kernel without causing lots of trouble.  I can think
of lots of potential panic()s that could arise here.  Does anyone have
any good ideas about the best way to try to approach modifying
vhangup()s behavior?

I guess the practical hack is to modify the shells to toggle DTR just
before they exit at logout.  This is NOT what I really want - I'm not
even sure if I can do that to /bin/sh - I'm sure another hack couldn't
hurt csh any!

Well, I guess I'll just go back and stare at the kernel code some more.
I'll either get a sudden inspiration or maybe just catch up on my
beauty sleep!

/Joe