I ran into a slight problem not related to renderpasses and compositing.
I'm trying to add a carpet into my scene using XGen. This all works fine untill I try to render it out. When I render with GI prototype I keep getting these warnings in my Renderlog:

running out of stack space, breaking shader call recursion

It doesn't brake the render but when I open the render in Photoshop the XGen hair is missing.
To figure out what is causing the warning I tried rendering it using Final Gather. This time I didn't get any warnings and when I opened the file in Photoshop the XGen hair was where it belongs.

So I guess GI prototype is not compatible with Xgen. Can anyone confirm this? Or is there some setting I missed?

Does anyone have a different or maybe better way of creating a carpet?

Here is an example of the carpet I'd like to create:



And here is my scene with the carpet shape (no hair or Xgen added):