Re: kern/57560: xennetback_xenbus.c rev 1.109 broke guests, causes DOM0 reboot

[Brad Spencer <brad%anduin.eldar.org@localhost>]

The following reply was made to PR port-xen/57560; it has been noted by GNATS.

From: Brad Spencer <brad%anduin.eldar.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: port-xen-maintainer%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
        netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/57560: xennetback_xenbus.c rev 1.109 broke guests, causes
 DOM0 reboot
Date: Fri, 04 Aug 2023 18:48:15 -0400

 Taylor R Campbell <riastradh%NetBSD.org@localhost> writes:
 
 > The following reply was made to PR port-xen/57560; it has been noted by GNATS.
 >
 > From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
 > To: Brad Spencer <brad%anduin.eldar.org@localhost>
 > Cc: gnats-bugs%NetBSD.org@localhost, martin%NetBSD.org@localhost
 > Subject: Re: kern/57560: xennetback_xenbus.c rev 1.109 broke guests, causes DOM0 reboot
 > Date: Fri, 4 Aug 2023 20:19:33 +0000
 >
 >  I reverted the commits on HEAD and pulled the revert up to netbsd-10,
 >  so the immediate problem should be addressed.
 >  
 >  However, the code is also slightly problematic because it's still
 >  missing a barrier in one place, and still using a much-too-expensive
 >  barrier (even on x86!) in the loop in another place, and still has
 >  several nonsensical barriers in other places that can't hurt
 >  correctness but do hurt understandability and maintainability.
 >  
 >  So I went through to try to redo the changes more carefully.  If you
 >  have the opportunity to test or bisect on another patch, I've drafted
 >  a series of changes, attached:
 >  
 >  - The .diff file is a single diff of the whole changes.  If it works,
 >    great -- I can commit.  But if not:
 >  
 >  - The .patch file is a series of individual changes for bisection to
 >    see exactly which one breaks it.
 >  
 
 
 I can help test this, but I am really out of time in the next 24 - 48
 hours at this point.  I expect that I may be able to do something in the
 next week at some point, just don't know when.
 
 
 Thanks very much for looking into this.
 
 
 -- 
 Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org