just in case this is different from the 'locking against myself' fixes
recently committed ...

i386 NetBSD 1.3K, slightly trimmed kernel based on GENERIC off the CDROM
image recently posted (thanks). I haven't layered any filesystems.
WARNING hand-copied; low S/N; no ECC

_panic(f0181d25,20002,f4b72d68,30002,1048) at _panic+0x57
_lockmgr(f4ba,30002,f4b72df4,f4bd1668,f01aa6f3) at _lockmgr+0x264
_ufs_lock(f4bd165c) at _ufs_lock+0x22
_vn_lock(f4b72d68,20002) at _vn_lock+0x3f
_uvn_io((f4b72d68,f4bd1c04,1,2,0) at _uvn_io+0x11d
_uvn_get(f4b72d68,0,f4bd1c80,f4bd1c80,f4bd1c84,0) at _uvn_get+0x196
_uvm_fault(f4a15630,400a,0,1,0) at _uvm_fault+0x6f
_trap() at _trap+0x40f
--- trap (number 6) ---
_copyin(2a28000,2000,f4bd1eec,1,f4b72df8) at _copyin+0x33
_ffs_write(f4bd1ea0,f4bd1f88,189612,f46c2004,f4bd1ea0) at _ffs_write+0x355
_vn_write(f4a2357c,f4a23594,f4bd1eec,f05d9f80,1) at _vn_write+0xd3
_dofilewrite(f4bc2004,3,f4a2357c,400a3000,189612) at _dofilewrite+0x81
_sys_write(f4bc2004,f4bd1f88,f4bd1f80,0,0) at _sys_write+0x43
_syscall() at _syscall+0x20e
--- syscall (number 4) ---