Persistent locking

I am a little confused about the current state of Keel's Persistent locking. 
The JavaDoc says that calling lock on a persistent keeps the persistent in an
exclusive read/write state.  

However, when I call lock on my Persistent, and then a little later I call
add()
on it, I notice that the add method hangs indefinitely while it tries to
require the lock.  I haven't releaed the lock before calling add() because I
want to still maintain the write exclusivity until my updates are commited. 
But I see that the Mutex class that Keel uses for locking does not support
reentrant locks.  I assume this means that once a thread calls aquire on the
lock, it can't do it again?  

Am I missing something?  Or does Keel need a reentrant locking mechanism? 

-Nate