misc/181323: reboot hang on 9.1-release, 9-stable

[Victor]

>Number:         181323
>Category:       misc
>Synopsis:       reboot hang on 9.1-release, 9-stable
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Aug 15 13:20:02 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Victor
>Release:        9.2-PRERELEASE
>Organization:
IF-INFOCOM
>Environment:
9.2-PRERELEASE #0 r254 247 amd64
>Description:
If any (slice?) mounted with userquota option system hang on reboot (shutdown -r now). Checked on two different PC (real i386 and virtualbox amd64). Symptoms like kern/172952 but i dont use zfs - ufs only. 
fstab without problem:

# Device        Mountpoint      FStype  Options Dump    Pass#
/dev/twed0p3    none            swap    sw      0       0
/dev/twed0p2    /               ufs     rw      1       1
/dev/twed0p4    /tmp            ufs     rw      2       2
/dev/twed0p5    /var            ufs     rw      2       2
/dev/twed0p6    /usr            ufs     rw    2       2

fstab with problem to reboot:

# Device        Mountpoint      FStype  Options Dump    Pass#
/dev/twed0p3    none            swap    sw      0       0
/dev/twed0p2    /               ufs     rw      1       1
/dev/twed0p4    /tmp            ufs     rw      2       2
/dev/twed0p5    /var            ufs     rw      2       2
/dev/twed0p6    /usr            ufs     rw,userquota    2       2
>How-To-Repeat:
Just mount any slice with userquota, reboot system and try shutdown -r now. You'll hang after "All buffers synced."
>Fix:
Dont know (remove userquota dont acceptable for me).

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