Re: call-process should not block process filters from running

[Eli Zaretskii]

> From: sbaugh@catern.com
> Date: Tue, 04 Jul 2023 09:51:42 -0400
> 
> >Timer functions should also avoid calling functions that cause Emacs to
> >wait, such as ‘sit-for’ (*note Waiting::).  This can lead to
> >unpredictable effects, since other timers (or even the same timer) can
> >run while waiting.
> 
> But it seems that the "(or even the same timer)" part is not true in
> practice.  From looking at timer-event-handler this makes sense - it
> looks like we remove the timer from timer-list before running it.  So
> timers don't run concurrently with themselves.  Which since it's already
> the case, we might as well formalize, since it's useful for Lisp
> programmers...

You cannot formalize that because a timer function can activate the
same timer again.

Also, there's a window before timer-event-handler removes the time
during which the same timer can still run.

Basically, once you allow to run Lisp, all bets are off...