bug#25247: 26.0.50; Concurrency crashes with XLib

["Elias Mårtenson" <lokedhs@gmail.com>]

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On 31 December 2016 at 19:05, Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Elias Mårtenson <lokedhs@gmail.com>
> > Date: Fri, 30 Dec 2016 19:21:08 +0800
> > Cc: Tino Calancha <tino.calancha@gmail.com>, raeburn@raeburn.org,
> 25247@debbugs.gnu.org
> >
> > One interesting fact is that if I replace ‘sleep-for’ with ‘sit-for’,
> then the updates come at exactly the expected
> > time.

But only as long as blink-cursor-mode is turned on, right?  If you
> turn it off before running the experiment, sit-for behaves the same as
> sleep-for, right?
>

I always turn off blink-cursor, but just to ensure that I was correct, I
tried to reproduce with -Q and that was very revealing.

With -Q and only turning off blink-cursor-mode, I get no updates until I
hit a key. With blink-cursor-mode on, it updates during the blinking phase
just as you suggested it would.


> When blink-cursor-mode is ON, it supplies 2 events each second, and
> that allows the threads that finished waiting to acquire the global
> lock and insert the string.  Otherwise, the threads wait for the
> global lock and do the insertions at the end.
>

I can only conclude that one of my millions of customisations triggers a
refresh at some interval that is rougly 4-5 seconds.

I also discovered that the event is actually triggered (i.e. the call to
sleep-for actually finishes on-time but it's just the buffer content that
are not updated). That makes things a lot more clear for me.

Now, this begs the question: Is this the appropriate behaviour? It would be
very nice if buffer updates made by threads were immediately updated on the
screen. If that is not possible for some reason, I think there should be
some way for Elisp code to force the repaint of a buffer.

Regards,
Elias

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