Subject: Re: Missed interrupts (fwd)
To: None <>
From: Holger Veit <>
List: current-users
Date: 11/29/1993 20:22:06
In Message-Id: <> (Amancio Hasty Jr) writes:

> he keyboard locked is probably due to the console driver (pccons or
> syscon) disabling the X mode for the X server.

Regarding the X locking this is infact the reason. There are other hardware
dependent problems that can cause an effect like this, but I observed
that they are not relevant for the majority of the reports. Total
keyboard failures from boot, however, can very well be caused by 
missing interrupts. The latter problem came up in 386bsd with the speedup
of the interrupt services by Bruce Evans that time.

The X lockup is caused by the double ill construction of the
cons.c multiplexor code together with the Bad Thing(TM) to pass raw 
data through the console tty channel (whether it is /dev/console or
/dev/"vga" is not relevant much). I never had this type of lockup with
codrv which uses a real /dev/kbd for that, but "the Net" "decided" to 
adopt the ill solution for the sake of some more subtly ill "features".

> This can be tested quite easily just exit out of the server via twm's
> menu. I have never seen a case except when the server or the system 
> crashes in which you can't exit out of the server. Forgot there is
> another case.
> If you are running kermit and have a session with a remote host,
> try to exit the server by pressing ctrl-alt-backspace, xinit    
> will hang and just about the only way to gain control of the       
> console is to kill the parent process of the login session.
> So something weird its happening with the com driver and killing
> a server.

This is probably a side influence of /dev/console. A "fix" could be 
to run all daemons, getty and X on /dev/vga, leaving /dev/console
alone. This is the proposed solution in the usenet, but unfortunately
it defeats the purpose of /dev/console entirely, including the 
"serial console" feature.


         Dr. Holger Veit                   | INTERNET:
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