Comment 80 for bug 1559308

This has been happening to me for about ~2 months too: hangs, typically after resuming from suspend, either immediately after resume or within a couple of minutes. Hard power-cycle by holding down power button is only way out (CTRL+ALT+F1 unresponsive and entire laptop appears frozen).

Think it's definitely related to external displays (I use a mini-DP cable) as I don't seem to have the issue when just using the laptop's internal screen.

Environment:
* ThinkPad X1 Carbon 3rd Gen (2015, Broadwell)
* Integrated Intel HD5500 graphics
* Stock Ubuntu 14.04/Unity with Kernel 3.19.

The attached crash log has no less than 2549 occurrences of the ominous "[drm:gen8_irq_handler [i915_bpo]] *ERROR* The master control interrupt lied (SDE)!". These tend to occur more often just before freezes and suggest the following might be related:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1488719