Comment 8 for bug 981304

More batch corruption, presuming:

commit c501ae7f332cdaf42e31af30b72b4b66cbbb1604
Author: Chris Wilson <email address hidden>
Date: Wed Dec 14 13:57:23 2011 +0100

    drm/i915: Only clear the GPU domains upon a successful finish

    By clearing the GPU read domains before waiting upon the buffer, we run
    the risk of the wait being interrupted and the domains prematurely
    cleared. The next time we attempt to wait upon the buffer (after
    userspace handles the signal), we believe that the buffer is idle and so
    skip the wait.