[PATCH] Ensure blitter quiescience before reading pixels from the framebuffer

[Daniel Stone]

On Tue, Jul 17, 2007 at 12:02:36PM +0100, Bernardo Innocenti wrote:
> On my laptop, I sometimes see trapezoids and glyphs painted in
> the wrong color.  It happens mostly in Gtk widgets, but I could
> reproduce the problem also with a small cairo testcase.
> 
> I can't test this fix right now because I'm travelling and I
> can't afford to download and build all the xserver prerequisites,
> but the race I'm fixing here would perfectly justify the symptoms
> I see.
> 
> Unfortunately, calling XSync() at this point will stall the GPU
> and has therefore a huge impact on performance.  But I can't
> think of another way to protect access.  If we're always going
> to accesse these 1x1 repeated pixmaps with the CPU, a better
> fix would be not uploading them in the first place.

You might start by mentioning which driver you're using?

Cheers,
Daniel
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