Re: Threads in emacs implementation

[Richard Stallman]

      Garbage collection also gets more interesting when 
    multiple threads are manipulating Lisp objects at a time.

In Emacs, GC doesn't have to happen at any particular point.
It is done as a regular housekeeping task.
So it could work well enough to set a flag telling all threads to wait 
once they come to a suitable stopping point, and GC once all threads
get there.