"panic: lockmgr: locking against myself" in 5.1-RELEASE-p11

Hi

	For some reason my computer running 5.1-RELEASE-p11 started to
panic. I made debugging kernel and have crashdump and debugging kernel
available.

	This panic, IMHO, seems to be related to background fsck.

	I have one extra fxp card which I can use in this machine and I
can setup a serial console connection to this machine if need be.

	dmesg from "boot -v" is attached. Unfortunately dmesg is too
large to fit into allocated space in kernel, so I dug relevant lines
from /var/log/messages.

	Here is list of kernel modules loaded
% kldstat
Id Refs Address    Size     Name
 1   15 0xc0100000 2c4a08   kernel
 2    1 0xc03c5000 45a4     snd_ich.ko
 3    2 0xc03ca000 1da98    snd_pcm.ko
 4    1 0xc03e8000 495d4    acpi.ko
 5    1 0xc6334000 a000     if_nv.ko
 6    1 0xc653e000 f000     miibus.ko
 7    1 0xc65eb000 20000    usb.ko
 8    1 0xc6639000 186000   nvidia.ko
 9    1 0xc67bf000 18000    linux.ko

if_nv.ko is from nvnet-1.0.0261_6
nvidia.ko is from nvidia-driver-1.0.4365

	Here is the backtrace

(kgdb) backtrace
#0  doadump () at /usr/src/sys/kern/kern_shutdown.c:238
#1  0xc01947f5 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:370
#2  0xc0194b2a in panic () at /usr/src/sys/kern/kern_shutdown.c:543
#3  0xc01232e2 in db_panic () at /usr/src/sys/ddb/db_command.c:448
#4  0xc012326e in db_command (last_cmdp=0xc02ddf40, cmd_table=0x0, 
    aux_cmd_tablep=0xc02d9590, aux_cmd_tablep_end=0xc02d9594)
    at /usr/src/sys/ddb/db_command.c:346
#5  0xc0123368 in db_command_loop () at /usr/src/sys/ddb/db_command.c:470
#6  0xc0125f78 in db_trap (type=3, code=0) at /usr/src/sys/ddb/db_trap.c:72
#7  0xc028bf70 in kdb_trap (type=3, code=0, regs=0xe0c054bc)
    at /usr/src/sys/i386/i386/db_interface.c:170
#8  0xc029cc07 in trap (frame=
      {tf_fs = 24, tf_es = 16, tf_ds = 16, tf_edi = 256, tf_esi = -969791104, tf_ebp = -524266232, tf_isp = -524266264, tf_ebx = 0, tf_edx = 0, tf_ecx = 32, tf_eax = 18, tf_trapno = 3, tf_err = 0, tf_eip = -1071070723, tf_cs = 8, tf_eflags = 646, tf_esp = -1070772662, tf_ss = -1070843711})
    at /usr/src/sys/i386/i386/trap.c:593
#9  0xc028d808 in calltrap () at {standard input}:96
#10 0xc0194aca in panic (fmt=0x0) at /usr/src/sys/kern/kern_shutdown.c:527
#11 0xc0188700 in lockmgr (lkp=0xd29aa8cc, flags=34144290, interlkp=0x2000020, 
    td=0xc6322980) at /usr/src/sys/kern/kern_lock.c:447
#12 0xc01ebec0 in BUF_TIMELOCK (bp=0xd29aa8cc, locktype=34144290, 
    interlock=0x0, wmesg=0x0, catch=0, timo=0) at buf.h:319
#13 0xc01e7758 in flushbuflist (blist=0xd29aa800, flags=4, vp=0xc6d19db0, 
    slpflag=0, slptimeo=0, errorp=0x0) at /usr/src/sys/kern/vfs_subr.c:1240
#14 0xc01e741f in vinvalbuf (vp=0xc6d19db0, flags=4, cred=0x0, td=0x0, 
    slpflag=0, slptimeo=0) at /usr/src/sys/kern/vfs_subr.c:1153
#15 0xc0232e7b in ffs_truncate (vp=0xc6d19db0, length=0, flags=2048, cred=0x0, 
    td=0xc6322980) at /usr/src/sys/ufs/ffs/ffs_inode.c:273
#16 0xc023664c in ffs_snapshot (mp=0xc6114800, snapfile=---Can't read userspace from dump, or kernel process---

)
    at /usr/src/sys/ufs/ffs/ffs_snapshot.c:664
#17 0xc0243e5f in ffs_mount (mp=0xc6114800, path=0xc657ec80 "/usr", data=0x0, 
    ndp=0xe0c05bf0, td=0xc6322980) at /usr/src/sys/ufs/ffs/ffs_vfsops.c:310
#18 0xc01e462e in vfs_mount (td=0xc6322980, fstype=0xc6d72130 "ffs", 
    fspath=0xc657ec80 "/usr", fsflags=18944000, fsdata=0x0)
    at /usr/src/sys/kern/vfs_mount.c:1090
#19 0xc01e3d98 in mount (td=0x0, uap=0xe0c05d14)
    at /usr/src/sys/kern/vfs_mount.c:846
#20 0xc029d491 in syscall (frame=
      {tf_fs = 47, tf_es = 47, tf_ds = 47, tf_edi = 0, tf_esi = -1077936704, tf_ebp = -1077936824, tf_isp = -524264076, tf_ebx = 135025830, tf_edx = -1, tf_ecx = 135025664, tf_eax = 21, tf_trapno = 12, tf_err = 2, tf_eip = 134568695, tf_cs = 31, tf_eflags = 514, tf_esp = -1077937204, tf_ss = 47})
    at /usr/src/sys/i386/i386/trap.c:1021
#21 0xc028d85d in Xint0x80_syscall () at {standard input}:138
---Can't read userspace from dump, or kernel process---

(kgdb) quit

-- 
"In the beginning the Universe was created. This has made a lot of
people very angry and been widely regarded as a bad move."
        -- Douglas Adams 1952 - 2001