With rc6 off the hangup happened 2 minutes after booting:
$ dmesg|grep i915 [ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.5.0-26-generic root=/dev/mapper/System-root ro quiet splash i915.i915_enable_rc6=0 vt.handoff=7 [ 0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.5.0-26-generic root=/dev/mapper/System-root ro quiet splash i915.i915_enable_rc6=0 vt.handoff=7 [ 0.857239] i915 0000:00:02.0: power state changed by ACPI to D0 [ 0.857242] i915 0000:00:02.0: power state changed by ACPI to D0 [ 0.857458] i915 0000:00:02.0: setting latency timer to 64 [ 0.877771] i915 0000:00:02.0: irq 44 for MSI/MSI-X [ 1.619983] [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on minor 0 [ 128.787009] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung [ 128.787013] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state [ 254.699283] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Seems it's time to return to 3.5.0-25-generic.
With rc6 off the hangup happened 2 minutes after booting:
$ dmesg|grep i915 /vmlinuz- 3.5.0-26- generic root=/dev/ mapper/ System- root ro quiet splash i915.i915_ enable_ rc6=0 vt.handoff=7 /vmlinuz- 3.5.0-26- generic root=/dev/ mapper/ System- root ro quiet splash i915.i915_ enable_ rc6=0 vt.handoff=7 hangcheck_ hung] *ERROR* Hangcheck timer elapsed... GPU hung dri/0/i915_ error_state hangcheck_ hung] *ERROR* Hangcheck timer elapsed... GPU hung
[ 0.000000] Command line: BOOT_IMAGE=
[ 0.000000] Kernel command line: BOOT_IMAGE=
[ 0.857239] i915 0000:00:02.0: power state changed by ACPI to D0
[ 0.857242] i915 0000:00:02.0: power state changed by ACPI to D0
[ 0.857458] i915 0000:00:02.0: setting latency timer to 64
[ 0.877771] i915 0000:00:02.0: irq 44 for MSI/MSI-X
[ 1.619983] [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on minor 0
[ 128.787009] [drm:i915_
[ 128.787013] [drm] capturing error event; look for more information in /debug/
[ 254.699283] [drm:i915_
Seems it's time to return to 3.5.0-25-generic.