Re: What's the problem?

[Richard Stallman]

    What we're talking about is basically multiple-stacks, context-switches
    done only from Feval (i.e. at elisp granularity so there's no concurrency
    in the C code),

The number of C functions that call Feval is rather large,
and include redisplay.  So this is not quite as easy as it might seem.

Redisplay could set a flag to prevent thread-switching.  That would
remove one large piece of the problem.  How big the problem remains
after that, I am not sure.