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[Bug 1076393] Re: Unity freezes when a program uses a lot of CPU and I hover an item on the launcher


The description of the bug fits ongoing problems I have experienced in
Ubuntu 12.04 for several months.

When several programs are running (Thunderbird, Chromium and evince are
frequently used on my system) compiz seems to stop responding. The
cursor continues to move with the mouse movement but the rest of the
screen is inactive and unresponsive to input. The keyboard is
unresponsive except that I can ctrl-Fn to another terminal and pull up
sudo top. It seems there is little activity but compiz is active.
Nothing seems to be abnormal except the X-window display is unresponsive
as described.

My solution has been to kill compiz with signal 3. When returning to the
X-window (ctrl-F7 typically) the interface will reset and allow me to
continue to work after the screen redraws. Compiz restarts itself and
the applications I had open redraw albeit not in the same position or
retaining their virtual window space.

 If X-windows becomes unresponsive again (except for the cursor) I can
switch to the terminal and kill compiz again. At some point this will
fail to work and something about compiz restarting itself seems to fail.
Apport never gets involved as there is no crash (I'm not sure how to
trigger apport to report the issue).

If this quasi-crash or freeze happening to others it may be unreported
and lead to user frustration and abandonment of compiz based interfaces
or ubuntu altogether. My suggestion is to formalize the python script
suggested by Davideddu.

I have been using this solution over the last 9 to 12 months. In the
last week after my latest aptitude upgrade I have had to use this rescue
method at typically twice an hour. The latest trigger seems to be  when
evince (3.4.0-0ubuntu1) is trying to startup or render a pdf.

This problem could use some heat. I'd like to help but am not sure how I

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  Unity freezes when a program uses a lot of CPU and I hover an item on
  the launcher

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