Subject: bug#32537: 26.1.50; Tramp: Cursor jumps when typing during asynchronous find-file

From: Eli Zaretskii <[email-masked]>
Date: Sun, 26 Aug 2018 21:32:10 +0300

> From: Gemini Lasswell <[email-masked]>
> Date: Sun, 26 Aug 2018 10:39:55 -0700
> 
> Then type "The rain in Spain falls mainly on the plain." or other
> sentence of your choice, over and over.  Stop when the message about
> checking vc-registered appears in the echo area.
> 
> Result: There will be a pause before the first typed text appears, then
> Emacs will start showing the typed text normally, except periodically
> the cursor will jump backwards so text will be inserted in the wrong
> place.

I guess some code in the background thread calls a yielding function
inside save-excursion or something?  I'd try running with a breakpoint
in set_point_both and temp_set_point_both, with commands that show the
backtrace and immediately continue the program.  Then you might see
the culprit.

Or maybe Michael will know where that happens given the description.

> After the first vc-registered message, Emacs will stop responding to
> input until after a buffer for one of the opened files is displayed.

That is not necessarily a bug: if some thread performs some prolonged
calculation, no other thread will be able to run, and no input will be
accepted.  Just like with a single thread.

Thanks.