Spawning new threads in Rails 3 / Phusion Passenger

I'm working on a Rails 3 app (running on Phusion Passenger) that is spawning new threads in a method.

Will those threads live in the process that spawned them, or will Passenger create a new process for them to live in? They will live in shared memory space at that point, so any variable sets by Thread One will be seen by Thread Two, right?