kernel deadlock on fstchg with vnd

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello,
do you have an idea on the problem in this thread:
http://mail-index.netbsd.org/port-xen/2022/05/27/msg010213.html

When stoping a Xen guest with virtual disk backed by a file,
the vnconfig -u process won't exit: it hangs on specio, and other processes
hang on fstchg.
From kernel messages, the xbd backed has closed the vnd device which is
being unconfigured, although I can't say if it did before or after
the vnconfig -u process was started (but likely before).

I can't reproduce this when using vnd from userland.

This happens with the file on /, or on a different partition,
with or without -o log. It happens even if the dom0 has a single CPU.

Any idea how to debug this further ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--