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

[sbaugh@catern.com]

Eli Zaretskii <eliz@gnu.org> writes:
>> 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.

Sure, but that's an explicit opt-in to running the timer again.  The
semantics could be "While a timer function is running, that timer is
deactivated; if you activate the timer in the timer function, it may run
again concurrently with the first run."

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

There are many ways to get rid of that window.