amd64/177633: FreeBSD 9.1 and ZFS deadlocked at shutdown/reboot

[Scott Kitchin]

>Number:         177633
>Category:       amd64
>Synopsis:       FreeBSD 9.1 and ZFS deadlocked at shutdown/reboot
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Apr 04 14:30:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Scott Kitchin
>Release:        9.1-RELENG r248699
>Organization:
Novysoft
>Environment:
FreeBSD web 9.1-RELEASE-p1 FreeBSD 9.1-RELEASE-p1 #0 r248699: Mon Mar 25 18:31:53 MSK 2013     root@:/usr/obj/usr/src/sys/NOVYSOFT  amd64

>Description:
I tried FreeBSD 9.1 (RELEASE/RELENG/STABLE) with ZFS mirrored (raid1) pool and iRedMail (http://www.iredmail.org) and it hangs when I issue a shutdown command. The only last message displayed "All buffers synched" and it hangs indefinitely until I hit the reset/power button.

FreeBSD 9.1 with ZFS (raid1) pool shutdown hang/deadlock.
FreeBSD 9.1 without ZFS shutdown successful.
FreeBSD 9.0 with ZFS shutdown successful.
FreeBSD 9.0 without ZFS shutdown successful.

This only happens after I install iRedMail. If I uninstall or delete iRedMail and it shutdowns normal. If I reinstall iRedMail and it hangs. iRedMail's mail daemons must be causing some kind of deadlock and preventing FreeBSD 9.1 from normal shutdown. I think this is serious problem if the server is at a remote location without physical access to power button.

I was able to reproduce this problem in VirtualBox with two virtual drives for ZFS pool mirroring and two different computers.

The server can be shutdown using this command 'shutdown -n -o -r now' but it's risky.
>How-To-Repeat:
1) Install FreeBSD 9.1 with ZFS mirrored (raid1) pools
2) Install Bash from ports
3) Install iRedMail from http://www.iredmail.org
4) Shutdown to start all services
5) Shutdown again and it hangs

I use ZFS creation tool from http://iceblood.googlecode.com/svn/FreeBSD_ZFS/freebsd_zfs_inst.sh
>Fix:
N/A

>Release-Note:
>Audit-Trail:
>Unformatted: