Re: multi-threaded Emacs

[Richard M Stallman]

    Actually, yielding in QUIT will take a lot of work.  It's definitely not
    "cooperative" seen from Elisp's point of view (where QUIT can be run
    implicitly all over the place).

I am surprised.  Perhaps you're right, but why do you think so?
Anywhere that calls QUIT is a place where it is safe for an error to happen,
so why not a thread switch?

A slightly more conservative approach would be to thread-switch from
QUIT on certain circumstances, such as, if the innermost
unwind-protect has calls to Lisp code inside it.  We could arrange
for the specpdl to have the requisite info.