amd64/175870: /etc/rc.d/netif restart cause system crash

[giepher]

>Number:         175870
>Category:       amd64
>Synopsis:       /etc/rc.d/netif restart cause system crash
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Feb 06 03:50:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     giepher
>Release:        9.1
>Organization:
iivnet.com
>Environment:
FreeBSD T420.giepher.com 9.1-PRERELEASE FreeBSD 9.1-PRERELEASE #0: Fri Nov  2 05:58:28 CST 2012     root@:/usr/obj/home/giepher/files/lnroot/usr/src/sys/GIEPHER_T420  amd64

>Description:
I'm using FreeBSD 9.1 PRERELEASE on Lenovo T420.  when iwn0 is open and wifi not be connected, run /etc/rc.d/netif restart  may cause system crash and automatic reboot.
>How-To-Repeat:
em0 offline
iwn0 offline
run /etc/rc.d/netif restart 
>Fix:


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