Re: Some experience with the igc branch

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: pipcet@protonmail.com,  ofv@wanadoo.es,  emacs-devel@gnu.org,
>   eller.helmut@gmail.com,  acorallo@gnu.org
> Date: Tue, 24 Dec 2024 15:12:40 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Now, with that definition, isn't specpdl stack part of "Lisp data"?
> > If so, and if we can safely access it from a signal handler, why do we
> > need to move it aside at all?  And how would the "message handler" be
> > different in that aspect from a signal hanlder?
> 
> We're coming from the problem that MPS uses signals for memory barriers.
> On platforms != macOS. And I am proposing a solution for that.
> 
> The SIGPROF handler does two things: (1) get the current backtrace,
> which does not trip on memory barriers, and (2) build a summary, i.e.
> count same backtraces using a hash table. (2) trips on memory barriers.

Can you elaborate on (2) and why it trips?  I guess I'm missing
something because I don't understand which code in record_backtrace
does trip on memory barriers and why.