I'm open to switching to a per-session lock of some sort, but I don'tI have a question on what you mean by "Only one session will be used
see a real need here. Only one session will be used as the backchannel
at a time, so there shouldn't be competing access between different
sessions for the cl_lock. We are competing with the other uses of the
cl_lock, but this one should be pretty quick. My preference would be to
add extra locking only once it becomes clear that it's necessary.