Re: multi-threaded Emacs

[Richard M Stallman]

    Internal data shared among threads must be accessed only inside critical
    sections in the .c code to have atomic operations on it.

I don't think we want to make such pervasive and inconvenient changes
in the C code.  What we want, I think, is to allow thread switches
only inside the QUIT macro.

Being able to program in terms of multiple threads will be useful for
situations such as multiple terminals.  However, I don't see much need
in Emacs for real parallelism.

    > It should not be hard to find all the existing threads and mark all
    > their stacks and specpdls.

    I like the Stefan's idea of stopping all running threads while the GC is
    executed, in this way we can use the current GC without big changes.
    At least until a concurrent [parallel] GC will be alive.

Making GCC handle the existence of multiple threads should be easy
with the approach I suggested above, once thread switching is
controlled.