Path: utzoo!dciem!nrcaer!xios!greg
From: greg@xios.XIOS.UUCP (Greg Franks)
Newsgroups: comp.unix.questions
Subject: Re: Unix (Microport) internal question
Message-ID: <448@xios.XIOS.UUCP>
Date: 18 Jan 88 17:20:42 GMT
Article-I.D.: xios.448
Posted: Mon Jan 18 12:20:42 1988
References: <2788@killer.UUCP> <169@sdeggo.UUCP>
Reply-To: greg@sdn.UUCP (Greg Franks)
Organization: XIOS Systems Corporation, Ottawa, Ontario, Canada
Lines: 28

In article <169@sdeggo.UUCP> dave@sdeggo.UUCP (David L. Smith) writes:

# In article <2788@killer.UUCP>, ajohnson@killer.UUCP (Andy Johnson) writes:
# > I have been running Microport's Unix V2.2 for about 7 months now
# > and have encountered the messages:
# >             tss fault
# >             double panic tss fault

#	This is the infamous serial port bug.  Apparently they are not masking
#out their interrupts properly and there is some kind of a race condition that
#gets set up.  This is a known and acknowledged bug.  They thought they had
#fixed it in 2.3, but apparently there is still a chance that this might
#come up.  It seems to be caused by running the serial ports at speeds above
#2400 baud.

The *real* reason for this scenario is kernel stack overrun.  (You were
likely doing console I/O at the time of the crash).  We increased the
size of the kernel stack (to 6k) which cured this fault in 2.2.  The
most likely cause of stack overrun in 2.2 systems is faulty interrupt
priority processing (recursive interrupts - fun wow!).  Interrupt
priorities have been fixed in 2.3. 

Disclaimer: We're at the opposite end of the continent from microport
systems. :-).  We do have source though.
-- 
Greg Franks             XIOS Systems Corporation, 1600 Carling Avenue,
(613) 725-5411          Ottawa, Ontario, Canada, K1Z 8R8
utzoo!dciem!nrcaer!xios!greg    "There's so much to sea in Nova Scotia"