Re: Opportunistic GC

[Eli Zaretskii <eliz@gnu.org>]

> From: Pip Cet <pipcet@gmail.com>
> Date: Wed, 10 Mar 2021 20:25:04 +0000
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>, Andrea Corallo <akrl@sdf.org>, emacs-devel@gnu.org
> 
> > There are other potential complications with this, related to
> > threads.  Posix says 'fork' only copies a single thread, the one that
> > called it, but what if that single thread is not the main thread?
> 
> Why would that be a problem?

Well, I mentioned one aspect that should be considered below.  There
are probably others, as we never intended for one of these threads to
be left alone.  E.g., what about error handling? non-main threads have
a very simplistic one.

> > In
> > Emacs nowadays a non-main Lisp thread can trigger GC.  What happens to
> > the mutexes we use in the threads machinery when we fork like that?
> 
> In the child, they're irrelevant

They are?  Don't you intend to send the results to the parent process?
or read some stuff from the parent?  Doesn't that mean you'd need to
call pselect?

> Everything should be fine...

Famous last words ;-)