bin/129760: after 'umount -f' of a stale NFS share FreeBSD locks up

[Eugene M. Zheganin]

>Number:         129760
>Category:       bin
>Synopsis:       after 'umount -f' of a stale NFS share FreeBSD locks up
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Dec 19 12:40:00 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Eugene M. Zheganin
>Release:        7.1-PRERELEASE
>Organization:
Norma JSC.
>Environment:
FreeBSD elm.norma.com. 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #0: Tue Dec 16 16:23:33 YEKT 2008     emz at ravenholm.hq.norma.perm.ru:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
I got a FreeBSD with some NFS shares mounted from the network. I decided to change its IP but forgot to umount NFS shares.

When trying to 'umount /mountpoint-of-a-nfs-share' without -f I got mount hanged up infinitely.
After successful umount -f I got the inability to log in via ssh, hanged up midnight commander, and 'reboot', issued from local console also hanged up. (Probably some other side effects had place too).

>How-To-Repeat:
Repeat similar actions.
>Fix:


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