The shutdown bug?

[Per olof Ljungmark]

As described in earlier reports, 9-STABLE sometimes cannot halt or
reboot properly.

FreeBSD 9.1-PRERELEASE #0 r241866: Mon Oct 22 16:28:47 CEST 2012

All ZFS file system, no NFS mounts. The problem occurs after updating
sources and rebuilding world for some reason the I suspect is connected
to the file system.

"shutdown -r now" or "halt -p" will stop after "Syncing discs" forever.
It is seen here on various HP boxes, DL360 G4, G5, XW6600 are examples.

Issuing a "shutdown -n -o -r now" works however and I assume this is not
too harmful with ZFS?

Setting sysctl hw.usb.no_shutdown_wait=1 does NOT fix the problem as
described in
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/167685

Should I file another bug or add to the existing?
Would it be useful to build a debug kernel, if yes, including what?

Thanks!

//per