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[Bug 740126] Re: Disabling an output can cause vblank events to be missed


I'm running on a ThinkPad T500 with dual video. Currently have been running with the build-in Intel graphics adaptor (due to battery life). I may switch to the external ATI Radeon 3850 (I think that's what my laptop has...) and test if that resolves the problem.

One theory I have is that the problem is related to the Compiz process
providing 3D graphics for Unity, and that this is related to the HW we
are running; i.e. if we run the Intel on-board graphics adaptor, it
might not have 3D support in HW, hence demanding other things from the
SW than if we run on 3D enabled graphics adaptors. Does this sound as a
possibility, anyone??

My solution to the problem (when coming back to my laptop with "frozen" screensaver) has been to press CTRL+ALT+F1 and then log in to the console in tty1. From here, I run ps -ef --sort time to see which processes have been running for a long time.
 1) kill <pid of gnome screen-saver> does not help --> doesn't even remove the screensaver photo from the display
     even though the process dies.
 2) kill <pid of compiz> does not kill the process --> no change
 3) kill -9 <pid of compiz> does actually kill compiz, and at this point pressing CTRL+ALT+F7 (or F8) takes me back to
     the Gnome session, which is now flashing a bit, then refreshing and coming up again, seemingly normal.

Most of the times, I'm able to get back into my session with all applications still running after step 3) above.
However, it has also happened that I got a new, blank session with no apps running.

My 5 cents today is that this is a problem related to compiz and 3D
rendering, and that it might be related to the graphics adaptor used,
including whether the computer is equipped with 3D suppot in HW.


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  Disabling an output can cause vblank events to be missed