bug#63407: 29.0.90; <mouse-2> on misspelled word hangs X11

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> merge 63406 63408 63404 63407
> thanks
>
>> From: Doug Maxey <emacs-bugs@maxeygroup.tech>
>> Date: Tue, 09 May 2023 16:15:09 -0500
>> 
>> 
>> The setup:
>> - rocky-9 x86_64.
>> - The graphics session is running in "classic", i.e. Xorg, not wayland.
>> - multi-monitors joined to single display.
>> - emacs-lucid from locally built rpm (non-rpm local build behaves same).
>> - buffer major-mode does not seem to matter.
>> - <mouse-2> on a misspelled word.
>> 
>> The result is other than having control of the sprite (the mouse can
>> move the sprite around normally. and I can switch tty with Ctrl-Alt-N)
>> there is NO other input accepted.  Cannot select any other window than
>> the last (emacs frame in this case), and there is no keyboard or mouse
>> button input.  There are no visible change on the screen, no dialog box
>> pops up.
>> 
>> The net effect is that the screen is frozen, save for the moving sprite.
>
> Please reproduce this, preferably in "emacs -Q", then attach GDB to
> the "frozen" Emacs process, and type at the GDB prompt:
>
>    thread apply all bt
>
> and post here everything that GDB prints as result.
>
> Thanks.

If an X server freeze occurs and is not remedied by killing Emacs (by
logging out), it's likely not Emacs's fault.  However, that the cursor
can continue to move suggests that a stray server grab may be involved,
which can be a problem with Emacs.

Doug, would you please tell me whether you are using an X compositing
manager, or if anything unusual is printed inside the X server logs?  If
not, would you please run Emacs under a tool like xscope, redirect its
output somewhere, and send it here?

Thanks.