bug#8065: Nexstep/Cocoa Emacs 23.2 hangs randomly on OSX

[Jonathan Rogers <jrogers@socialserve.com>]

I use GNU Emacs 23.2.1 (x86_64-apple-darwin10.6.0, NS 
apple-appkit-1038.35) built by the Macports package emacs-app @23.2.

All Emacs frames frequently becomes unresponsive and no commands can be 
executed. Cursors appear as hollow boxes as if the window is unfocused. 
Any click on a frame generates an OSX beep noise. C-g and all other 
keypresses are totally ignored.

Strangely, the menus continue to open and commands can be selected, 
though they mostly have no effect. The only menu commands that seem to 
have any effect are the Emacs -> Hide Emacs and Emacs -> Hide Others 
commands. This would seem to indicate that though some part of the 
Nextstep GUI is still working, the main Emacs loop is not or it has 
become disconnected from the GUI.

In this state, Emacs takes very little CPU time. The only way I can 
cause Emacs to end when it's in this state is to use OSX's "Force quit" 
or Unix command like kill or pkill.

Though I find Emacs in this state frequently, it's triggered very 
intermittently and I haven't determined a clear pattern. Sometimes, I 
can use it with no hangs for several hours, but it generally happens at 
least once a day.

It may be related to switching between Emacs and other applications or 
running subprocesses. I have encountered it several times when running a 
command in Magit, which runs git as a subprocess, but the same commands 
usually succeed. Other sub-processes, such as Bash and ack seem to have 
no trouble.
-- 
Jonathan Ross Rogers