Re: Concurrency via isolated process/thread

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: emacs-devel@gnu.org
> Date: Wed, 05 Jul 2023 11:23:40 +0000
> 
> AFAIU, it is possible to create shared memory only readable by child
> processes.
> 
> Then, exchanging data between the two Emacs processes may be done using
> memcpy to/from shared memory.
> 
> It may be dumb (I have no experience with processes in C), but I have
> something like the following in mind:
> 
> 1. Main Emacs process has a normal Elisp thread that watches for async
>    Emacs process requests.
> 2. Once a request arrives, asking to get/modify main Emacs process data,
>    the request is fulfilled synchronously and signaled back by writing
>    to memory accessible by the async process.

That solves part of the problem, maybe (assuming we'd want to allow
shared memory in Emacs).  The other parts -- how to implement async
process requests so that they don't suffer from the same problem, and
how to reference objects outside of the shared memory -- are still
there.

> > I have, too many of them.  Some are semi-fixed, but I'm afraid we only
> > don't hear about them because threads are not used in serious,
> > production-quality programs.
> 
> You are talking about bugs?

Bugs that are there "by design".

> If nobody goes far enough to discover those,
> they are probably not the real reason why people do not use Elisp threads.

I'm saying that it could be the other way around: we don't hear about
those bugs because threads are not used seriously.