From owner-freebsd-scsi  Sun Mar 24 15:34:49 1996
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To: swhite@xwing.wcape.gov.za (Sean White)
cc: freebsd-scsi@freebsd.org
Subject: Re: SCSI bus hangs - AIC7870 (fwd) 
In-reply-to: Your message of "Sun, 24 Mar 1996 22:32:38 +0100."
             <199603242132.WAA05745@uriah.heep.sax.de> 
Date: Sun, 24 Mar 1996 15:34:38 -0800
From: "Justin T. Gibbs" <gibbs@freefall.freebsd.org>
Sender: owner-freebsd-scsi@freebsd.org
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>Oh, I've captured the message that the machine comes up with just as it
>hangs. This is while doing 'mt rewind' :-
>
>ahc0: target 0, lun 0 (sd0) timed out
>st0(ahc0:1:0): BUS DEVICE RESET message queued.
>ahc0: target 0, lun 0 (sd0) timed out

What version of the driver are you using?  Do you have disconnection
*enabled* in SCSI-Select for your tape drive?  Does your tape drive
even support disconnection?

The problem looks like your tape drive is not disconnecting (leaving the
bus free) while it does a rewind, so all writes to your hard drive are
delayed beyond the maximum timeout period for sd commands (10 seconds)
and you get the timeout and all hell breaks loose.  You would have
to increase the timeouts in the sd code in order to kludge around this
if you tape will not disconnect.

>Regards,
>Sean (about to shoot this machine!) White.
>

--
Justin T. Gibbs
===========================================
  FreeBSD: Turning PCs into workstations
===========================================