Bug#565344: Found a second workaround

[Bruno Kleinert]

Am Dienstag, den 02.02.2010, 16:08 +0100 schrieb Bruno Kleinert: 
> A further experiment to collect information:
> 
> On the Intel notebook I tried blindly to restore gamma values from the
> KMS framebuffer text console with DISPLAY=:0.0 xgamma -gamma 1.0 but
> that didn't bring back neither the framebuffer console nor the X session
> when I tried to switch to it.
> 
> Only Blindly unlocking the GNOME screensaver and issuing the xgamma
> command restores the gamma values for the X session and also the KMS
> framebuffer text. Btw.: Also at the framebuffer console when I issued
> the xgamma command before, xgamma claimed that the gamma settings
> already were all set to 1.0 for R, G and B.
And some other news from tests:

After installing xserver-xorg-video-radeon and mesa 7.7, both from
experimental, the AMD/ATI machine is able to run compiz (Works really
surprisingly stable - but that's off topic here ;).

I installed compiz packages also on the Notebook with Intel GPU. To my
surprise *both* machines could suspend and resume without any black
screen at all! I don't have too many suspend/resume cycles until now,
but ATM it seems as if both machines resume reliably when they're
running compiz.

Ok, I think it's time to write a little summary for those interested in
trying to reproduce the "black screen after resume" ;)

      * Tested with: AMD/ATI GPU on amd64 system and all Intel stuff
        with Intel GPU on i386 system 
      * KMS or no KMS -- on both systems it doesn't matter.
      * Software - that likely is - involved: Metacity, configured as
        compositing manager (Use gconf-editor to
        set /apps/metacity/general/compositing_manager to 'true') and
        GNOME screensaver 
      * Before doing any testing, I suggest to set up a short key that
        starts a terminal and make sure that new windows get the input
        focus, you might find that quite useful afterwards...
      * Suspend the machine to disk by the freaky GNOME shutdown dialog.
        Before the machine switches to either the VGA or KMS framebuffer
        text console, GNOME screensaver should softly fade the screen to
        black 
      * Now resume the box and there should be back a running and
        responsive system with a black screen. Also X *and* VGA and KMS
        framebuffer consoles should remain black! 
      * The GNOME screensaver should be running on the all black X
        session -- Try unlocking it blindly with your password 
      * Hopefully one has configured the short key to fire up a terminal
        window. Press that shortcut and blindly execute 'xgamma -gamma
        1' -- You should have normal output on the screen in X and at
        the VGA or KMS framebuffer text console. When everything is
        back, one should see, that xgamma also prints the gamma settings
        as they were BEFORE the command was issued. It should say, that
        RGB channeles were set to 1.0 all the time.
      * My current workaround? Install compiz, suspend, resume and there
        should be no black screen anymore!

My conclusion: It's hardware and driver independent, so it's likely to
be a bug in the core xserver. ...and somehow the usage of AIGLX by
compiz works around that issue. So, I'm stuck here and have no further
clue what else to test or look at.

Cheers - Fuddl
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