X locks when deactivating composite effects

[Lubos Lunak]

On Tuesday 11 of November 2008, Michel Dänzer wrote:
> On Mon, 2008-11-10 at 06:35 -0800, john terragon wrote:
> > Hi,
> >
> > whenever I deactivate the composite effects the x server locks up and I
> > get the following in the Xorg log file:
...
> Yes, looks like https://bugzilla.redhat.com/show_bug.cgi?id=445331
> (http://bugs.freedesktop.org/show_bug.cgi?id=7128 is probably related,
> http://bugs.freedesktop.org/show_bug.cgi?id=18465 possibly).
>
> Basically, the problem is that the (AI)GLX code keeps pointers to
> DrawableRec structs of X windows corresponding to GLX windows without
> preventing/tracking the destruction of the X windows. So it can happen
> that the (AI)GLX code dereferences these pointers after the X window is
> already destroyed.
>
> It might be possible for the client (is that kwin for you as well?) to
> avoid this problem by making sure that the GLX context is unbound and
> destroyed before the X window is destroyed, not sure about that though.

 The bug appears to be in X (GLX1.3 docs seem to suggest in section 3.3.7 ["If 
draw is destroyed after glXMakeContextCurrent is called,..."] that destroying 
a window while a GLXContext using it is still current is allowed). I'll try 
to reshuffle the relevant KWin code though.

-- 
Lubos Lunak
KDE developer
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