kern/38760: umount -f /usr panics the system

[christos%zoulas.com@localhost]

>Number:         38760
>Category:       kern
>Synopsis:       umount -f /usr panics the system
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon May 26 16:20:00 +0000 2008
>Originator:     Christos Zoulas
>Release:        NetBSD 4.99.63
>Organization:
        None
>Environment:
NetBSD shiny.astron.com 4.99.63 NetBSD 4.99.63 (SHINY) #142: Mon May 26 
00:13:21 EDT 2008  
christos%shiny.astron.com@localhost:/usr/src/sys/arch/i386/compile/SHINY i386
Architecture: i386
Machine: i386
>Description:
        ffs_reclaim->genfs_node_destroy->rw_destroy->rw_abort
>How-To-Repeat:
        DIAGNOSTIC,DEBUG,LOCKDEBUG kernel
        bring up system multi-user, then umount -f /usr
>Fix:
        ?