processes stuck in vmo_de state

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Hi,

I have recently upgraded my home storage box (Avoton based board
running FreeBSD/amd64) from 10.0-RELEASE (patched with some ZFS
changes) to -CURRENT.  It looks like the system would easily hang when
I start 'buildworld', when this happens, I saw sh process stuck in
'vmo_de' state and procstat -kk would give me EBUSY:

$ procstat -kk 1752
  PID    TID COMM             TDNAME           KSTACK

procstat: sysctl: kern.proc.kstack: 1752: Device busy

To rule out issue introduced by my local changes, I reverted them all
and used an unpatched 'VT' kernel (with WITNESS, etc. enabled).

In loader.conf I have:

zfs_load="YES"
aesni_load="YES"
hint.apic.0.clock=0
hint.atrtc.0.clock=0

In rc.conf I have:

powerd_enable="YES"

economy_cx_lowest="LOW"
performance_cx_lowest="LOW"

The zpool I'm using is configured to use SHA256 as checksum.  One
zpool is created over 4 GELI provider and decrypted on boot but I
don't think that matters.

Any hints?  The system have flaky IPMI access so I can't always debug
from remote but would happy to provide more data if helpful.

Cheers,
-----BEGIN PGP SIGNATURE-----
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=xBqp
-----END PGP SIGNATURE-----