Re: igc, macOS avoiding signals

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: pipcet@protonmail.com,  emacs-devel@gnu.org
> Date: Sat, 28 Dec 2024 14:28:57 +0100
> 
> Sean Devlin <spd@toadstyle.org> writes:
> 
> > To be clear, I should make sure to include the above commit in my
> > build? Or should I not include it?
> 
> Just let in in. I reverted it only in my Emacs.

Can you show that MPS runs GC from a non-main thread?  Like, if you
set a breakpoint in ArenaEnter, does it ever break on a non-main
thread?

I've just reviewed all the backtraces we had in our MPS discussions,
and all I see there is MPS being triggered either from igc_on_idle or
from alloc_impl, but every single time it happens on the main thread,
the one where I see the main function that enters recursive-edit.

So maybe Pip is right, and MPS always runs in the main (Lisp) thread,
even on macOS?  Can you catch it on a non-main thread?