Overlays and OpenLDAP multi-threading model

Hi!

I'm starting to see how overlays works to write one. But I've got a doubt and I'm asking to be sure: Is the overlay stack called within each thread ? If so, I think it can't block an entire thread pool, right ?

My concern is about performance. The overlay I'm writing will only take place in some backend data modifications but it can be quite slow in terms of OpenLDAP connection handling, because it will be communicating via IPC with another process... If this overlay blocks only one connection, it's ok. But if it's blocks an entire thread pool, I'll have to figure out another solution.

Thanks a lot in advance Lucas Brasilino