Re: kern/54045: mpii driver triggers panic on timeout in physio

[Frank Kardel <kardel%netbsd.org@localhost>]

The following reply was made to PR kern/54045; it has been noted by GNATS.

From: Frank Kardel <kardel%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/54045: mpii driver triggers panic on timeout in physio
Date: Wed, 6 Mar 2019 13:46:26 +0100

 I agree with you. I have cleaned up the mpii driver a bit with respect 
 to error/status/resid handling - I will commit that soon afte some testing.
 
 This cleanup will need to be pulled up to -8 also.
 
 Frank
 
 
 On 03/06/19 13:35, Michael van Elst wrote:
 > The following reply was made to PR kern/54045; it has been noted by GNATS.
 >
 > From: mlelstv%serpens.de@localhost (Michael van Elst)
 > To: gnats-bugs%netbsd.org@localhost
 > Cc:
 > Subject: Re: kern/54045: mpii driver triggers panic on timeout in physio
 > Date: Wed, 6 Mar 2019 12:31:56 -0000 (UTC)
 >
 >   kardel%netbsd.org@localhost writes:
 >   
 >   >>Description:
 >   >	Timeouts on SCSI WRITE/READ commands in the mpii driver cause physio to panic with:
 >   >	kernel diagnostic assertion "bp->b_error == 0" failed: file "/src/NetBSD/cur/src/sys/kern/kern_physio.c", line 179
 >   
 >   
 >   The adapter driver doesn't hold that assertion. You can get a partial
 >   transfer and an error condition at the same time from SCSI. Some error
 >   paths in some drivers reset xs->resid, but that's not used very consistently.
 >   
 >   The sd driver assures that the physio assertion is satisfied in sddone(),
 >   but the tape driver doesn't.
 >   
 >   The assertion itself is also something "new". The original code would
 >   accept a partial read (usually an EOM condition) that could also return
 >   an error.
 >   
 >   The combination of drivers that reset the residual after an error and
 >   an assertion that checks the fake residual is a bit strange too.
 >   
 >   
 >   --
 >   --
 >                                   Michael van Elst
 >   Internet: mlelstv%serpens.de@localhost
 >                                   "A potential Snark may lurk in every tree."
 >