On Tue, 2008-11-18 at 00:38 -0800, Keith Packard wrote:
> Airlied pointed me at a fairly easy bug to reproduce -- VT switch while
> compiz is running and the server locks up when you switch back.

No such problem here with radeon.


> The cause is fairly simple to understand -- VT switching involves a mode
> set, and that mode set erases the hardware frame counter registers.
> However, Mesa doesn't know that, and so it asks to wait for the next
> frame to pass by when compiz asks it to wait. As it has an old frame
> count, it waits for a long time.
> 
> It seems like what we want is for the kernel to keep some kind of
> 'offset' when vt switching and add that into the frame counts returned
> for each crtc. Does this make sense?
> 
> We've got DRM_PRE_MODESET and DRM_POST_MODESET as well as
> I915_GEM_LEAVEVT/I915_GEM_ENTERVT to play with here.

This is precisely what DRM_PRE/POST_MODESET are for. Assuming
xf86-video-intel is calling them appropriately before and after VT
switch, this is probably a bug in the i915 DRM.


-- 
Earthling Michel Dänzer           |          http://tungstengraphics.com
Libre software enthusiast         |          Debian, X and DRI developer


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