it's one of these commits (from the quantal kernel), likely the top one since it's happening on sandybridge:
817e8fdee14b05d drm/i915: Implement WaDisableHiZPlanesWhenMSAAEnabled 4c443ec9afe7f6f drm/i915: GFX_MODE Flush TLB Invalidate Mode must be '1' for scanline waits f534135423c7028 drm/i915: Disable AsyncFlip performance optimisations c0c1fd8a18479f0 drm/i915: Invalidate the relocation presumed_offsets along the slow path ** Changed in: linux (Ubuntu) Importance: Medium => Critical ** Changed in: linux (Ubuntu) Assignee: (unassigned) => Ubuntu Kernel Team (ubuntu-kernel-team) ** Also affects: linux (Ubuntu Precise) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Quantal) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Raring) Importance: Critical Assignee: Ubuntu Kernel Team (ubuntu-kernel-team) Status: Confirmed ** Changed in: linux (Ubuntu Quantal) Importance: Undecided => Critical ** Changed in: linux (Ubuntu Quantal) Status: New => Confirmed ** Changed in: linux (Ubuntu Precise) Importance: Undecided => Critical ** Changed in: linux (Ubuntu Precise) Status: New => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1140716 Title: [regression] 3.5.0-26-generic GPU hangs To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1140716/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs