Comment 69 for bug 445056

Looking through the dmesg, we see the symptom of the hang in that the i915 kernel worker thread and Xorg are both blocked trying to acquire a mutex. This implies that a third unknown process is currently waiting on the GPU. As the hangcheck has not fired, it implies that the GPU is idle. So is this a case of missing interrupts? In which case the recent gen3 page-flipping patches from Jesse Barnes may be of use.