11.0-BEAGLEBONE-r264670: "lock order reversal" warning on shutdown

[Winston Smith]

Using u-boot-2013.04 and FreeBSD-armv6-11.0-BEAGLEBONE-r264670, I was
able to boot from the SD card on a BBB.  Upon shutdown, I see the
following on the console:


root at beaglebone:/boot/msdos # /sbin/halt
Apr 19 00:02:33 beaglebone halt: halted by root
Apr 19 00:02:33 beaglebone syslogd: exiting on signal 15
Waiting (max 60 seconds) for system process `vnlru' to stop...done
Waiting (max 60 seconds) for system process `bufdaemon' to stop...done
Waiting (max 60 seconds) for system process `syncer' to stop...
Syncing disks, vnodes remaining...2 0 1 0 1 0 0 0 done
All buffers synced.
lock order reversal:
 1st 0xc2e58a54 ufs (ufs) @ /usr/src/FreeBSD-CURRENT/sys/kern/vfs_mount.c:1237
 2nd 0xc2e64394 devfs (devfs) @
/usr/src/FreeBSD-CURRENT/sys/fs/msdosfs/msdosfs_vfsops.c:989
KDB: stack backtrace:
db_trace_self() at db_trace_self
pc = 0xc0542258  lr = 0xc02324bc (db_trace_self_wrapper+0x30)
sp = 0xde6d4a18  fp = 0xde6d4b30
r10 = 0xc2e64394
db_trace_self_wrapper() at db_trace_self_wrapper+0x30
pc = 0xc02324bc  lr = 0xc039b358 (kdb_backtrace+0x38)
sp = 0xde6d4b38  fp = 0xde6d4b40
r4 = 0xc0689484  r5 = 0xc059401b
r6 = 0xc0594a31  r7 = 0xc05b3bdd
kdb_backtrace() at kdb_backtrace+0x38
pc = 0xc039b358  lr = 0xc03b5c78 (witness_checkorder+0xe50)
sp = 0xde6d4b48  fp = 0xde6d4b98
r4 = 0xc059fa6d
witness_checkorder() at witness_checkorder+0xe50
pc = 0xc03b5c78  lr = 0xc034829c (__lockmgr_args+0x8b4)
sp = 0xde6d4ba0  fp = 0xde6d4c08
r4 = 0x00000000  r5 = 0x00080400
r6 = 0x000003dd  r7 = 0xc2e643b4
r8 = 0xc2e64394  r9 = 0x00080000
r10 = 0xc0594a2e
__lockmgr_args() at __lockmgr_args+0x8b4
pc = 0xc034829c  lr = 0xc03fa524 (vop_stdlock+0x3c)
sp = 0xde6d4c10  fp = 0xde6d4c20
r4 = 0xde6d4c40  r5 = 0xc0660df0
r6 = 0x00000000  r7 = 0x00080400
r8 = 0xde6d4c40  r9 = 0x00080300
r10 = 0x000003dd
vop_stdlock() at vop_stdlock+0x3c
pc = 0xc03fa524  lr = 0xc056c8a4 (VOP_LOCK1_APV+0xd8)
sp = 0xde6d4c28  fp = 0xde6d4c38
VOP_LOCK1_APV() at VOP_LOCK1_APV+0xd8
pc = 0xc056c8a4  lr = 0xc0418980 (_vn_lock+0x44)
sp = 0xde6d4c40  fp = 0xde6d4c70
r4 = 0xc2e64360  r5 = 0x00000001
r6 = 0xc0594a2e
_vn_lock() at _vn_lock+0x44
pc = 0xc0418980  lr = 0xc02aa314 (msdosfs_sync+0x1a0)
sp = 0xde6d4c78  fp = 0xde6d4cd0
r4 = 0xde6d4c9c  r5 = 0x00000001
r6 = 0xc2d09960  r7 = 0xc2a962b0
r8 = 0x00000000  r9 = 0x00080300
r10 = 0xc2dfe700
msdosfs_sync() at msdosfs_sync+0x1a0
pc = 0xc02aa314  lr = 0xc0402958 (dounmount+0x464)
sp = 0xde6d4cd8  fp = 0xde6d4d20
r4 = 0xc2e58a20  r5 = 0x00000000
r6 = 0x00000000  r7 = 0x00000000
r8 = 0xc2d09960  r9 = 0x00080000
r10 = 0x00080000
dounmount() at dounmount+0x464
pc = 0xc0402958  lr = 0xc040b164 (vfs_unmountall+0x48)
sp = 0xde6d4d28  fp = 0xde6d4d48
r4 = 0xc2d09960  r5 = 0xc059fa6d
r6 = 0xc05a41ab  r7 = 0xc2a962b0
r8 = 0xc0661080  r9 = 0xc05c1a76
r10 = 0xc05b4c36
vfs_unmountall() at vfs_unmountall+0x48
pc = 0xc040b164  lr = 0xc03640e4 (kern_reboot+0x468)
sp = 0xde6d4d50  fp = 0xde6d4da8
r4 = 0xc066d024  r5 = 0x00000000
r6 = 0xc05a41ab  r7 = 0xcd2156a8
r8 = 0x00000008  r9 = 0x00000000
r10 = 0xc092ea58
kern_reboot() at kern_reboot+0x468
pc = 0xc03640e4  lr = 0xc0363c74 ($d)
sp = 0xde6d4db0  fp = 0xde6d4db8
r4 = 0xde6d4e18  r5 = 0xc2aa1640
r6 = 0x00000000  r7 = 0x00000000
r8 = 0x00000000  r9 = 0xde6d4e10
r10 = 0x00000004
$d() at $d
pc = 0xc0363c74  lr = 0xc0557878 (swi_handler+0x284)
sp = 0xde6d4dc0  fp = 0xde6d4e58
r4 = 0xc2d09960
swi_handler() at swi_handler+0x284
pc = 0xc0557878  lr = 0xc0543d74 (swi_exit)
sp = 0xde6d4e60  fp = 0xbffffd00
r4 = 0x00000004  r5 = 0x00000002
r6 = 0xbffffcdc  r7 = 0x00000037
r8 = 0x00000000  r9 = 0x00000000
swi_exit() at swi_exit
pc = 0xc0543d74  lr = 0xc0543d74 (swi_exit)
sp = 0xde6d4e60  fp = 0xbffffd00
Unable to unwind further
Uptime: 20m13s

The operating system has halted.
Please press any key to reboot.