bug#1753: emacs may cause window manager to hang

[Paul Graham]

Dear Emacs Support:

I am using emacs version:

   GNU Emacs 22.2.1 (i386-redhat-linux-gnu, GTK+ Version 2.12.9)
   of 2008-05-23 on xenbuilder4.fedora.phx.redhat.com

I am running Fedora 9, kernel 2.6.27.9-73.fc9.i686, GNOEM 2.22.3 on a
Dell vostro 1710.

I am using two screens -- a Dell monitor is virtually above the laptop
screen.  Several times the computer has frozen up while I'm running
ediff within emacs.  The computer gets into a state where I can't
change the input focus.  Only one window has the focus.  If that
window is an xterm or emacs then I can try killing emacs manually, but
even then there remains a blank window where emacs was, and I still
can't change the focus.  Menus don't respond either.  The only
solution is to reboot.

The bug seems to be reproducible as follows.  I have the emacs window
in the lower, desktop screen, but with the top of the emacs window
close to the top of the screen.  I start ediff, usually with
ediff-buffers.  The little ediff window appears at the bottom of the
upper screen, since it can't fit above the emacs window in the lower
screen.  From that point on, the window focus is broken.

It seems that having the main emacs in the lower screen and the ediff
window in the upper screen is what causes the behavior described above.
If I keep the emacs window away from the top of the lower screen, so
that there is room for the little ediff window to fit in the lower
screen, then the problem does not occur.

Maybe emacs has nothing to do with this bug -- maybe it is only
exposing a bug in the window manager.  Any suggestions?

Paul