Deadlock in 5.3p5

[Peter Jeremy]

My son's computer deadlocked last night.  "show lockedvnods" in DDB showed:

Locked vnodes
0xc1669840: tag ufs, type VDIR, usecount 8, writecount 0, refcount 2, flags (VV_ROOT|VV_OBJBUF), lock type ufs: EXCL (count 1) by thread 0xc18ed000 (pid 9666) with 7 pending
      ino 2, on dev ad0s1g (4, 25)
0xc1682000: tag ufs, type VDIR, usecount 5, writecount 0, refcount 2, flags (VV_OBJBUF), lock type ufs: EXCL (count 1) by thread 0xc16fd000 (pid 15686) with 1 pending
      ino 23552, on dev ad0s1g (4, 25)
0xc1b30d68: tag ufs, type VDIR, usecount 2, writecount 0, refcount 1, flags    (VV_OBJBUF), lock type ufs: EXCL (count 1) by thread 0xc268f000 (pid 9075) with 1 pending
      ino 122986, on dev ad0s1g (4, 25)
0xc1c3c210: tag ufs, type VDIR, usecount 3, writecount 0, refcount 1, flags    (VV_OBJBUF), lock type ufs: EXCL (count 1) by thread 0xc16fe4b0 (pid 9067) with 1 pending
      ino 142022, on dev ad0s1g (4, 25)
0xc1e2ce70: tag ufs, type VREG, usecount 6, writecount 0, refcount 0, flags (VV_OBJBUF), lock type ufs: SHARED (count 1) with 1 pending
      ino 142169, on dev ad0s1g (4, 25)

After poking around in the crashdump for a while, I've worked out that
the process holding each of the above exclusive locks is waiting on
the next lock in the list.  Unfortunately, there doesn't appear to be
any way to work out which process is holding the shared lock unless
DEBUG_LOCKS is set (and even this doesn't work if the lock was implicitly
downgraded by a process calling lockmgr(LK_SHARED) when it holds an
exclusive lock).

FWIW, the affected inodes are:
     2  /usr
 23552  /usr/local
122986  /usr/local/OpenOffice.org1.1.4
142022  /usr/local/OpenOffice.org1.1.4/program
142169  /usr/local/OpenOffice.org1.1.4/program/libpsp645fi.so

Does anyone have any ideas on how to track this further (or so I just
write it off as a glitch).

-- 
Peter Jeremy