Comment 295 for bug 1140716

Mikhail, for the time being you can set i915.semaphores=0 (or echo 0 > /sys/modules/i915/parameters/semaphores) to prevent this hang.

The only interesting patch I can suggest atm is

commit 31643d54a739382626c27c0f2a12b3bbc22d1a38
Author: Ben Widawsky <email address hidden>
Date: Wed Sep 26 10:34:01 2012 -0700

    drm/i915: Workaround to bump rc6 voltage to 450

    BIOS should be setting the minimum voltage for rc6 to be 450mV. Old or
    buggy BIOSen may not be doing this, so we correct it for them. Ideally
    customers should update the BIOS as only it would know the optimal
    values for the platform, so we leave that fact as a DRM_ERROR for the
    user to see.

in 3.8-rc1 or look for a BIOS update.