[500] in linux-scsi channel archive
Re: Errors & Unit Attention
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Sat Aug 12 16:47:49 1995
Date: Sat, 12 Aug 95 13:45 EDT
From: eric@aib.com (Eric Youngdale)
To: "Leonard N. Zubkoff" <lnz@dandelion.com>
Cc: linux-scsi@vger.rutgers.edu
>I don't think it's quite this simple. As I read the code in sd.c, this only
>happens for disk devices that are marked "removable". An ordinary disk falls
>through that case and eventually prints an error message. I'm still not clear
>on what happens after that error, though. Processes frequently hang with a "D"
>status, and all further file system access to the disk fails. Why?
This is all true. If this happens for a disk that is marked
not removeable, I suspect a bug somewhere.
The general idea is that further commands will be blocked
until the command that was executing and caused an error completes.
There are a couple of ways of debugging this. One is to build the
user-mode simulator and program the scsi_debug driver to simulate the
disk change, and the other is to simply try and debug the running
kernel. To start with, it would probably be easier to debug the
kernel.
The place to start is in sd.c in the function rw_intr(). This
is the interrupt service routine, and we should come up here when we
see the unit attention. Offhand it looks a bit fishy to me at the moment,
and I suspect that this is where the problem lies. Let me study it some,
and I will get back to you.
-Eric
