kern/136944: [lor] bufwait/snaplk (fsync)

[Rene Ladan]

>Number:         136944
>Category:       kern
>Synopsis:       [lor] bufwait/snaplk (fsync)
>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 Jul 20 21:30:05 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Rene Ladan
>Release:        8.0-BETA2 amd64
>Organization:
>Environment:
FreeBSD self.rene-ladan.nl 8.0-BETA2 FreeBSD 8.0-BETA2 #0: Wed Jul 15 21:48:41 UTC 2009     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

>Description:
lock order reversal: 
 1st 0xffffff8029490410 bufwait (bufwait) @ /usr/src/sys/kern/vfs_bio.c:2558
 2nd 0xffffff0078f4a130 snaplk (snaplk) @ /usr/src/sys/ufs/ffs/ffs_snapshot.c:2223
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
__lockmgr_args() at __lockmgr_args+0xcf3
ffs_copyonwrite() at ffs_copyonwrite+0x189
ffs_geom_strategy() at ffs_geom_strategy+0x1b5
bufwrite() at bufwrite+0x106
ffs_update() at ffs_update+0x1bd
ffs_fsync() at ffs_fsync+0x43
fsync() at fsync+0x148
syscall() at syscall+0x1af
Xfast_syscall() at Xfast_syscall+0xe1
--- syscall (95, FreeBSD ELF64, fsync), rip = 0x80084cd0c, rsp = 0x7fffffffdcb8, rbp = 0x1 ---

>How-To-Repeat:
GENERIC kernel, only devfs and UFS2 filesystems mounted via /dev/ad* (/ , /var, /tmp, /usr)
>Fix:


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