kern/154266: LOR between (ufs) vfs_mount.c and (devfs) ffs_vfsops.c

[Olivier Certner]

>Number:         154266
>Category:       kern
>Synopsis:       LOR between (ufs) vfs_mount.c and (devfs) ffs_vfsops.c
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jan 24 15:30:09 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Olivier Certner
>Release:        9.0-CURRENT-201101
>Organization:
Private
>Environment:
FreeBSD 9.0-CURRENT-201101 #0: Mon Jan  3 22:15:39 UTC 2011 root at farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
This LOR appears when mounting a USB key (I think the slice had a UFS filesystem, but not completely sure). It doesn't seem to have been reported in any other PR.

lock order reversal:
 1st 0xfffffe0003e6b818 ufs (ufs) @ /usr/src/sys/kern/vfs_mount.c:1210
 2nd 0xfffffe00166f3638 devfs (devfs) @ /usr/src/sys/ufs/ffs/ffs_vfsops.c:1266
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
kdb_backtrace() at kdb_backtrace+0x37
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x807
__lockmgr_args() at __lockmgr_args+0xd42
vop_stdlock() at vop_stdlock+0x39
VOP_LOCK1_APV() at VOP_LOCK1_APV+0x9b
_vn_lock() at _vn_lock+0x47
ffs_flushfiles() at ffs_flushfiles+0xb5
ffs_unmount() at ffs_unmount+0x70
dounmount() at dounmount+0x2dc
unmount() at unmount+0x28e
syscallenter() at syscallenter+0x1aa
syscall() at syscall+0x4c
Xfast_syscall() at Xfast_syscall+0xe2
--- syscall (22, FreeBSD ELF64, unmount), rip = 0x800b6c67c, rsp = 0x7fffffffeaa8, rbp = 0x7fffffffebc0 ---

>How-To-Repeat:
Mount some USB key with a UFS filesystem on it.
>Fix:
None.

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