Re: kern/53385 (vnconfig deadlock on fstchg)

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

The following reply was made to PR kern/53385; it has been noted by GNATS.

From: Brad Spencer <brad%anduin.eldar.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost,
        bouyer%antioche.eu.org@localhost
Subject: Re: kern/53385 (vnconfig deadlock on fstchg)
Date: Mon, 22 Feb 2021 07:15:17 -0500

 "Greg A. Woods" <woods%planix.ca@localhost> writes:
 
 > The following reply was made to PR kern/53385; it has been noted by GNATS.
 >
 > From: "Greg A. Woods" <woods%planix.ca@localhost>
 > To: NetBSD GNATS <gnats-bugs%NetBSD.org@localhost>
 > Cc: 
 > Subject: Re: kern/53385 (vnconfig deadlock on fstchg)
 > Date: Fri, 19 Feb 2021 14:07:20 -0800
 >
 >  > >How-To-Repeat:
 >  > 	destroy a domU with 2 file-backed disks ?
 >  
 >  Definitely that.
 >  
 >  I just ran "halt -p" in just such a domU (four LVM disks and two
 >  file-backed disks) and instantly everything in the dom0 got hung in
 >  "fstchg", including all login shells.
 >  
 >  The dom0 host is running NetBSD/amd64 8.99.32 (kernel from about
 >  2019/11/28).
 
 I see this problem on a 8.99.25 NetBSD DOM0.  However, I thought I also
 saw a commit where this was fixed (I may also be misremembering this)
 and I may remember that it made it into 9.x.  I am not currently in a
 position to try a newer DOM0 NetBSD, but it may be worth attempting that
 if you can.
 
 >  
 >  (Thankfully other domUs running on the same machine appear to still be
 >  running and apparently can still access their LVM-backed disks, so I
 >  think I can shut them down before crashing the dom0 -- BUT the dom0 is
 >  remote and I don't have easy console access!)
 >  
 >  > >Fix:
 >  > 	workaround: make sure Xen won't call more than one vnconfig -u at
 >  > 	once. But we need a fix for this.
 >  
 >  Seriously!
 >  
 >  -- 
 >  					Greg A. Woods <gwoods%acm.org@localhost>
 >  
 >  Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
 >  Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>
 >  
 
 
 
 -- 
 Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org