I have temporarily patched union_root() so that it unlocks the mount point
before locking the root of the union, then re-locks the mount point
immediately afterwards.  I'm sure this isn't The Right Thing To Do, but it
was the easiest, and it seems to work -- after removing the forced delays
from my X startup scripts, I have been in and out of X several times now
without any deadlock.

Many thanks to both of you for your help in getting to the root of the
problem (pun unintended).  I'll leave the Official fix up to the kernel
maintenance crew, but let me know if you'd like me to test any
modifications you come up with.

Best regards,

-----------------------
Trevin Beattie          "Do not meddle in the affairs of wizards,
trevin@xmission.com     for you are crunchy and good with ketchup."
      {:->                                     --unknown