Disks Hang Under 2.0.2 SCSI

[steve at cdp.UUCP]

SUMMARY -- README
-------
We have been experiencing regular crashes running under
Interactive 2.0.2 with 3 SCSI disks on an aha1542a.  Later in
this message is a script which crashes our machine.  The
purpose of this message is to find other people who are
willing to try to replicate these crashes on various
machines.  I encourage folks to try out the script, even if
they do not have our exact hardware configuration.  This will
help us to better understand the whether the problem lies in
hardware or in 2.0.2.  

DETAILS
-------
The symptom of the crashes is that all processes continue to
run, but any process that goes for the disk hangs.  So, getty
prints the login prompt, and accepts a name at login:, but
when it goes to spawn login, the exec hangs the system.
Switch to a different virtual console, and repeat the same
thing.  emacs works fine until it tries to auto-save, open
a file, etc...

The crashes occurs intermittently -- about once a day on our
machine that averages 20 users at a time and is up 24 hours a
day.

On an alternate machine, I have developed a little program
that can reliably crash the machine with 3 or more disks within
about 2 seconds of invocation.  The program looks like this :

-----------------------------------------------------------
:
# crashix.sh
#
#   hangs  i/386 2.0.2 SCSI driver within 2 seconds.
#   Assume root partition on /dev/dsk/0s1, other
#   partitions on /dev/dsk/1s3 and  /dev/dsk/2s3.
#
sync
sync
dd if=/dev/dsk/0s1 bs=128k >/dev/null &
dd if=/dev/dsk/1s3 bs=128k >/dev/null &
dd if=/dev/dsk/2s3 bs=128k >/dev/null &
----------------------------------------------------------

Notes :
   o It is important to have all of the dd's in the background,
     so that they all have the same priority.  The occurence
     of crashes is related disk use intensity; having processes
     with lower priority reduces the disk use intensity and crash
     frequency.

   o You may have different partitioning on your disks.  Change
     the device names to suit your configuration.  Try it with
     2 3 or 4 disks.

   o Our hardware configuration is :
       - Mylex MI-386/20 motherboard, 8MB RAM on board.

       - aha1542a SCSI host adapter
          4 CDC 94161 150MB SCSI disks
          1 Archive 2150s "VIPER" cartridge drive

       - a hercules card.

   o I have tried crashix.sh with three  other motherboards
     (two based on recent Chips & Technologies chip sets),
     and the behaviour is the same (crash within 2 seconds).


Support at interactive OEM division has returned calls, but
skeptical that this is software-related.  

Thanks for your help.  If people that test their machines
keep me informed, I will post the results to the net.  


Steve Fram

Chief Programmer
Community Data Processing (CdP)
{hplabs, pyramid, ...}!cdp!steve
(415)-322-9069