Comment 7 for bug 1231207

I thought this was going to be related to

commit b16999da214803a026d7246ec4aa62031e82dfc8
Author: Chris Wilson <email address hidden>
Date: Wed Oct 9 23:54:57 2013 +0100

    sna: Upon unwinding operations, also check for exec objects to clear

    If we cancel an operation after partially committing it, we may leave
    the batch bookkeeping in an inconsistent state with an exec object with
    a zero-length batch. Ordinarily, this would not be an issue as we could
    pass the extra object to the next batch. However, if we switch rings, we
    need to clear the extra objects as they are currently flagged as being
    on the wrong ring, leading to hilarity.

    Reported-by: Jiri Slaby <email address hidden>
    Signed-off-by: Chris Wilson <email address hidden>

Maybe it still is...