Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!cornell!rochester!udel!mmdf
From: Dickson@his-phoenix-multics.arpa (Paul Dickson)
Newsgroups: comp.os.minix
Subject: Re: AN HISTORIC MOMENT!
Message-ID: <3295@louie.udel.EDU>
Date: 14 Jul 88 14:57:17 GMT
Sender: mmdf@udel.EDU
Lines: 26

>From Andy Tanenbaum (ast@cs.vu.nl):
>...you can get a slave terminal running on RS232 port 1 at 9600 baud,
>and that works fine as terminal.  Whether it could do file transfers at
>that speed as another matter.  I have tested MINIX with the console plus
>the second terminal, and it seems to work fine.

How well did you test your tty.c with the second terminal?

I ask because when we were following the design outlined in the original
tty.c, we discovered a fairly serious problem.  If more than one process
does output on a serial port, those processes will hang.  It's possible
that you totally rewrote the serial part of tty.c to get around this
problem, but we haven't seen your code yet.

The screen console has the same problem, but it's fortunate to be able
to complete output before returning.

The problem is that only the last process to do output to the port will
be given the wakeup when output in complete.  This means that if more
than one process does output, all but one will never be re-awakened.

We have an idea on how to get around the problem.  We'll try it this
weekend if time permits.  The answer seems to be in buffer management.

          -Paul Dickson

Arpanet:  Dickson%pco @ BCO-Multics.ARPA