bug#34179: 27.0.50; message hangs when buffer with process visible

[martin rudalics]

> Maybe producing a profile of such a hang could give us some hints.

I somehow suspect that it's caused by a message that gets displayed
causing the minibuffer to resize and 'window--adjust-process-windows'
to react in some strange way.  Michael's

> Run till exit from #0  redisplay_internal () at xdisp.c:14716
> echo_area_display (update_frame_p=true) at xdisp.c:11715
> 11715                    unbind_to (count, Qnil);

brought me to that idea.

martin