bug#61667: 29.0.60; Failure to redisplay

[Gregory Heytings]

> > . "emacs -Q", then type 'a' (which visits a file?)
> > . "emacs" with your configuration, then type "C-x b", which visits a file
> >
> > In both cases, you see a delay before the display is updated, right?
>
> About 1 in 5-10 tries the delay is high enough to be noticeable 
> (200-300ms with -Q and up to 1-2 seconds with my config).

What happens if instead of your recipe you use these ones

emacs -Q --eval "(tool-bar-mode -1)" --eval "(menu-bar-mode -1)" --eval "(scroll-bar-mode -1)" --eval 
"(global-set-key \"a\" (lambda () (interactive) (message "a pressed!") (find-file \"test.c\")))"

emacs -Q --eval "(tool-bar-mode -1)" --eval "(menu-bar-mode -1)" --eval "(scroll-bar-mode -1)" --eval 
"(global-set-key \"a\" (lambda () (interactive) (find-file \"test.c\") (message "file loaded!")))"

?