FreeBSD deadlock

[Scott Kitchin]

I want to report that FreeBSD 9.1 (release/releng/stable) is having 
problem with ZFS and iRedMail.  I was able to reproduce this on three 
machines including virtualbox but I don't have debugging skill to do this.

1) FreeBSD 9.1 (release/releng/stable)
2) ZFS in raid1 configuration.  I created swap partition outside of ZFS 
and no change.
3) Installed iRedMail mail server from http://www.iredmail.org/

Before installing iRedMail, FreeBSD and ZFS are working normal. After I 
installed iRedMail and rebooted the server to load iRedMail configs.  I 
rebooted the server again and it hangs after "All buffers synced".

I did the above again with FreeBSD 9.0 and it work normal and 
reboot/shutdown without hang.

This problem is easy to reproduce since I tried different configurations 
and disabled many modules including usb in kernel as well.  FreeBSD 9.1 
and iRedMail reboot/shutdown normal without ZFS.

Scott