kern/41078: mounting ext2fs via vnd causes LOCKDEBUG panic

[Christoph_Egger%gmx.de@localhost]

>Number:         41078
>Category:       kern
>Synopsis:       mounting ext2fs via vnd causes LOCKDEBUG panic
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 26 16:05:00 +0000 2009
>Originator:     Christoph Egger
>Release:        NetBSD/amd64 5.99.8
>Organization:
>Environment:
>Description:

Lockdebug panic happens when mounting ext2fs via vnd.

Reader / writer lock error: lockdebug_unlocked: no shared holds on this lock

lock address : 0xffff80004eea4d20 type     :     sleep/adaptive
initialized  : 0xffffffff80711166
shared holds :                  0 exclusive:                  0
shares wanted:                  0 exclusive:                  0
current cpu  :                  0 last held:                  0
current lwp  : 0xffff80004f4d97e0 last held: 000000000000000000
last locked  : 0xffffffff8070ea52 unlocked : 0xffffffff8070ead8
owner/count  : 000000000000000000 flags    : 0x0000000000000008

Turnstile chain at 0xffffffff80ce89e0.
=> No active turnstile for this lock.

panic: LOCKDEBUG
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff802388c5 cs 8 rflags 246 cr2  7f7ffd96ecb0 cpl 0
rsp ffff80004f4fe650
Stopped in pid 435.1 (mount_ext2fs) at  netbsd:breakpoint+0x5:  leave
db{0}> bt
breakpoint() at netbsd:breakpoint+0x5
panic() at netbsd:panic+0x289
lockdebug_abort1() at netbsd:lockdebug_abort1+0xd3
rw_exit() at netbsd:rw_exit+0xe9
vlockmgr() at netbsd:vlockmgr+0xd8
VOP_UNLOCK() at netbsd:VOP_UNLOCK+0x64
spec_open() at netbsd:spec_open+0x340
VOP_OPEN() at netbsd:VOP_OPEN+0x62
ext2fs_mount() at netbsd:ext2fs_mount+0x25a
VFS_MOUNT() at netbsd:VFS_MOUNT+0x44
do_sys_mount() at netbsd:do_sys_mount+0x62d
sys___mount50() at netbsd:sys___mount50+0x33
syscall() at netbsd:syscall+0xb6

>How-To-Repeat:

vndconfig -c vnd0 linux.img
mount -t ext2fs /dev/vnd0a /mnt

>Fix: