[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

Michel Dänzer <michel@daenzer.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Product|xorg                        |DRI
            Version|git                         |unspecified
          Component|Driver/Radeon               |DRM/Radeon
         AssignedTo|xorg-driver-ati@lists.x.org |dri-devel@lists.freedesktop
                   |                            |.org
          QAContact|xorg-team@lists.x.org       |

--- Comment #2 from Michel Dänzer <michel@daenzer.net> 2011-04-07 02:58:34 PDT ---
Looks like one of the pointers in radeon_legacy_backlight_get_brightness() is
NULL, but I'm not sure which one that could be. Johannes, can you add some
debugging output to see which one it is?

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

Johannes Obermayr <johannesobermayr@gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #45356|0                           |1
        is obsolete|                            |

--- Comment #3 from Johannes Obermayr <johannesobermayr@gmx.de> 2011-04-07 07:27:13 PDT ---
Created an attachment (id=45373)
 --> (https://bugs.freedesktop.org/attachment.cgi?id=45373)
dmesg

(In reply to comment #2)
> Looks like one of the pointers in radeon_legacy_backlight_get_brightness() is
> NULL, but I'm not sure which one that could be. Johannes, can you add some
> debugging output to see which one it is?

boot parameter: drm.debug=255 nomodeset 3
then a 'rmmod radeon'
and finally a 'modprobe radeon'

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

--- Comment #4 from Michel Dänzer <michel@daenzer.net> 2011-04-07 07:51:26 PDT ---
Thanks, but I mean modifying radeon_legacy_backlight_get_brightness() to print
the value of each pointer before dereferencing it. If you don't know how to do
that, I can try whipping up a test patch.

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

--- Comment #5 from Michel Dänzer <michel@daenzer.net> 2011-04-07 08:35:56 PDT ---
Created an attachment (id=45386)
 View: https://bugs.freedesktop.org/attachment.cgi?id=45386
 Review: https://bugs.freedesktop.org/review?bug=36037&attachment=45386

Debugging patch

This patch (only compile tested) should print the pointer values before
referencing them, and bail if one of them is NULL. This should also avoid the
immediate crash, but it might still crash elsewhere later on.

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

Johannes Obermayr <johannesobermayr@gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #45373|0                           |1
        is obsolete|                            |

--- Comment #6 from Johannes Obermayr <johannesobermayr@gmx.de> 2011-04-07 10:03:15 PDT ---
Created an attachment (id=45392)
 --> (https://bugs.freedesktop.org/attachment.cgi?id=45392)
dmesg

dmesg output with applied Debugging patch

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

--- Comment #7 from Johannes Obermayr <johannesobermayr@gmx.de> 2011-04-07 11:00:32 PDT ---
After a second and third try (after reboots) I got:

[drm] pdata=00000072

I assume it is the value I receive each time now.

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

--- Comment #8 from Michel Dänzer <michel@daenzer.net> 2011-04-14 07:59:21 PDT ---
So bl_get_data() returns NULL in radeon_legacy_backlight_get_brightness(). I'm
stumped as to how that could happen... Any ideas, Matthew?

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

--- Comment #9 from Matthew Garrett <mjg59@srcf.ucam.org> 2011-04-14 08:29:30 PDT ---
That's bizarre. I can't see any obvious way this could happen.

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[Bug 36037] RV250Lf: airlied/drm-fixes branch crashes in new backlight code

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=36037

Johannes Obermayr <johannesobermayr@gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #10 from Johannes Obermayr <johannesobermayr@gmx.de> 2012-01-04 05:06:07 PST ---
It does not crash when building against recent kernels.

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