There's probably a better forum for talking about the dispatch library code, but since I found the problem while trying 
to build an unloadable LSM, I'll report it here.

The dispatch_destroy() code does not free the select->ctrl->coid.  Thus, after some number of cycles of  select_attach()
/select_detach()/dispatch_destroy(), select_attach() fails with EMFILE.

I added a ConnectDetach in dispatch_destroy(), and that solved my immediate problem.  I guess you could argue both ways 
about select_detach() noticing that the coid was no longer needed and and dealing with it at that point, but it seems 
like it should be dealt with at least in dispatch_destroy.

Murf