If the backing pixmap for a window is migrated between video and system RAM, its serial number is updated but the corresponding window's is not. If a GC is validated before the pixmap is migrated and then used again afterward, VALIDATE_DRAWABLE_AND_GC will decide not to validate it because its serial number matches the window's. This can lead to rendering corruption or segfaults when the wrong GC ops are used to perform the rendering.
We have a workaround for this in the nvidia driver now, so Release Wranglers, if you decide not to care about this issue then go ahead and mark the bug WONTFIX.
It might be nice to come up with a fix for this, but I don't think it's critical for release, if NVIDIA has managed to work around it. Removing from blocker list with agreement from submitter.
I've fixed the ops to validate the backing gc/drawable if the serial number has been bumped, fixing a reproducable instance of this bug with XAA. I think that covers it, so marking closed.
*** Bug 7246 has been marked as a duplicate of this bug. ***
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