[492] in linux-scsi channel archive
Re: Errors & Unit Attention
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Thu Aug 10 22:44:09 1995
From: "Eric Youngdale" <eric@aib.com>
Date: Thu, 10 Aug 1995 10:16:57 -0400
In-Reply-To: "Leonard N. Zubkoff" <lnz@dandelion.com>
"Errors & Unit Attention" (Aug 9, 8:10pm)
To: "Leonard N. Zubkoff" <lnz@dandelion.com>
Cc: linux-scsi@vger.rutgers.edu
On Aug 9, 8:10pm, Leonard N. Zubkoff wrote:
> Subject: Errors & Unit Attention
> What is supposed to happen if a SCSI disk has a power glitch and then
returns
> Unit Attention? I would think that the operation should eventually be
retried,
> but I seem to be seeing all further normal access to that device hang,
even
> though scsiinfo is still able to talk to the device just fine. How about
if a
> driver sends a Bus Device Reset to the disk device? I'm trying to resolve
some
> reported problems with error recovery in my new BusLogic driver, but it
seems
> the problems might not be driver level at all. Comments?
A unit attention is treated as a media change, as this is the way
that these things are normally reported. The reason you are locked out from
the drive is that the kernel is assuming that you do not have the same media
in the drive as was in there when the disk was mounted. If you unmount the
disk and remount it, you should get access again.
Normally you cannot distinguish the different causes of unit
attention on a scsi-I device, but sometimes scsi-II devices send additional
information to indicate what is going on. We currently do not look for
this, but it would be in the sense information that is sent back from the
drive
if it is present at all. I suppose we could look for this and if it is
present we could attempt to be a bit more smart about it.
-Eric
--
"The woods are lovely, dark and deep. But I have promises to keep,
And lines to code before I sleep, And lines to code before I sleep."
