kern/39385: unmount_ptyfs vrele deadlock.

[christos%zoulas.com@localhost]

>Number:         39385
>Category:       kern
>Synopsis:       unmounting ptyfs with busy ptys causes deadlock in vrele
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 20 09:40:00 +0000 2008
>Originator:     Christos Zoulas
>Release:        NetBSD 4.99.71
>Organization:
        Disorganized Anonymous
>Environment:
System: NetBSD quasar.astron.com 4.99.71 NetBSD 4.99.71 (QUASAR) #53: Thu Jul 
31 11:31:34 EDT 2008 
christos%quasar.astron.com@localhost:/usr/src/sys/arch/amd64/compile/QUASAR 
amd64
Architecture: x86_64
Machine: amd64
>Description:
        running reboot from a ptyfs pty causes a deadlock in vrelel()?

>How-To-Repeat:
        start x and a couple of xterms. run reboot on one of them.
>Fix:
        unknown.