machine wedged -> KDB: enter: lock violation

[Kris Kennaway]

Brad Pitney wrote:
> Not sure why it keeps wedging, at first I thought it was something to
> do with the  LORs, now after adding some more debugging options I
> think I might have found the answer!
> 
> KDB: stack backtrace:
> db_trace_self_wrapper(c074b5ee,e70599ac,c05b6853,c4a9e000,e70599ac,...)
> at db_trace_self_wrapper+0x26
> kdb_backtrace(c4a9e000,e70599ac,c07025c5,e70599bc,c4c44d98,...) at
> kdb_backtrace+0x29
> vfs_badlock(c4a37900,e70599bc,c07b00a0,c4c44d98,c4a9e000) at vfs_badlock+0x23
> assert_vop_elocked(c4c44d98,c0752ee7,c4a9e000,1b9,0,...) at
> assert_vop_elocked+0x53
> cache_lookup(c4c4815c,e7059bc0,e7059bd4,e7059bc0,c4aa4400,...) at
> cache_lookup+0x53c
> vfs_cache_lookup(e7059aa8,c07545ba,c4c4815c,2,c4c4815c,...) at
> vfs_cache_lookup+0xaa
> VOP_LOOKUP_APV(c4a37900,e7059aa8,c4a9e000,c075356a,19b,...) at
> VOP_LOOKUP_APV+0xe5
> lookup(e7059bac,e7059ae8,c6,bf,c4aa542c,...) at lookup+0x53e
> namei(e7059bac,2,c0754d92,c0577808,c0811ae0,...) at namei+0x28e
> kern_stat(c4a9e000,2820258c,0,e7059c1c,c074d152,...) at kern_stat+0x3d
> stat(c4a9e000,e7059cfc,8,c074e1dc,c0785e00,...) at stat+0x2f
> syscall(e7059d38) at syscall+0x273
> Xint0x80_syscall() at Xint0x80_syscall+0x20
> --- syscall (188, FreeBSD ELF32, stat), eip = 0x281aa48f, esp =
> 0xbfbfea4c, ebp = 0xbfbfeae8 ---
> cache_lookup: 0xc4c44d98 is not exclusive locked but should be
> KDB: enter: lock violation
> 
> Locked vnodes

[...]

Apparently 0xc4c44d98 is not locked at all, it didnt appear in your 
list.  Are you sure that was all of it?  What does 'show vnode 
0xc4c44d98' report?

This is likely to be a unionfs bug.

Kris