LOR On AMD64 hosted by KVM hypervisor

Hey All,
I am seeing a repeated LOR on r291495 that is pretty reproducible.  This
happens right after the system boots:

lock order reversal:
 1st 0xfffffe03e37fa920 bufwait (bufwait) _at_ /usr/src/sys/kern/vfs_bio.c:3476
 2nd 0xfffff80024c72200 dirhash (dirhash) _at_
/usr/src/sys/ufs/ufs/ufs_dirhash.c:281
stack backtrace:
#0 0xffffffff80a7b2e0 at witness_debugger+0x70
#1 0xffffffff80a7b1e1 at witness_checkorder+0xe71
#2 0xffffffff80a28ab2 at _sx_xlock+0x72
#3 0xffffffff80cc0a5d at ufsdirhash_add+0x3d
#4 0xffffffff80cc390f at ufs_direnter+0x62f
#5 0xffffffff80ccccd3 at ufs_makeinode+0x5f3
#6 0xffffffff80cc881d at ufs_create+0x2d
#7 0xffffffff80fb2ed1 at VOP_CREATE_APV+0xf1
#8 0xffffffff80ae3568 at vn_open_cred+0x2f8
#9 0xffffffff80adc8ec at kern_openat+0x25c
#10 0xffffffff80e6a4fe at amd64_syscall+0x2de
#11 0xffffffff80e4972b at Xfast_syscall+0xfb

Here is the system info:
% uname -ar
FreeBSD bsd-current.trp-srd.com 11.0-CURRENT FreeBSD 11.0-CURRENT #0
r291495: Mon Nov 30 23:14:34 UTC 2015
root_at_releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

The server itself is a VM running under the KVM hypervisor.  I am
currently rebuilding world+kernel now.  The base OS image is from the
latest 11-CURRENT snapshot, and I have been able to reproduce this on
several hypervisors.

Has anyone else seen this?

Cheers,
-pete




-- 
Pete Wright
pete_at_nomadlogic.org
twitter => _at_nomadlogicLA