My Q67 / i7-2600 box has rev09 Sandy Bridge graphics.  It hangs
instantly when GNOME loads and it hangs so hard the reset button
doesn't work.  Setting i915.semaphore=0 fixes it.

Semaphores were disabled in a1656b90
in 2.6.38 and were re-enabled by

commit 47ae63e0
Merge: c59a333f 467cffba
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Mar 7 12:32:44 2011 +0000

    Merge branch 'drm-intel-fixes' into drm-intel-next

    Apply the trivial conflicting regression fixes, but keep GPU semaphores
    enabled.

    Conflicts:
        drivers/gpu/drm/i915/i915_drv.h
        drivers/gpu/drm/i915/i915_gem_execbuffer.c

(It's worth noting that the offending change is i915_drv.c,
 which is not a conflict.)
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Acked-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>