mod_rails: what MPM model should Apache use?

When using mod_php in Apache 2+ it is important to use the MPM-prefork
version of Apache, because some PHP extensions are not thread-safe.

But what about mod_rails? Can it use MPM-worker (multithreading), or
does it also need MPM-prefork?

I've read other places, that Rails is not thread-safe. Does this afflict
the choice?

- Carsten

At the moment Phusion Passenger only supports the prefork MPM. Later
versions will also support the worker MPM. Whether Ruby on Rails is
thread-safe is totally irrelevant to Passenger.