First, the only lock we can use for the time being is the database lock,
because if we use some other lock we could deadlock.
That said, it seems like we could avoid using a lock at all. The purpose
of the lock was to eliminate double-lookups, but if we have to acquire
the database lock to check if we need to do the lookup, we've lost the
advantage of doing so at all.
We *could* just do a traditional check-lock-check pattern to get the
lock far less often, but given that we're likely going to acquire it
during startup, even a single access has the possibility of really
gumming up the works.
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