laptop completely locks up on video/display changes

[Barton Janes]

Description: Ubuntu 18.04.1 LTS
Release: 18.04
Package: linux-image-4.15.0-44-generic
Hardware: Dell Precision 5530 with Dell Thunderbolt Dock

Latest round of updates added kernel 4.15.0-44. On reboot the kernel hangs the laptop, have to do a full hard shutdown then start. Laptop will start and run fine when not docked. When docked to Dell Thunderbolt dock with 2 external monitors connected by mini display port and HDMI the laptop will lock up hard with any change to primary display. If I boot with laptop open and display running, laptop works fine unless I try closing lid to use just the external displays, this will completely lock up the system. If I open system settings and re-arrange the displays or change the primary display, the system will lock up hard. Nothing is found in logs. Booting with the laptop closed not using the laptop display, system will completely lock after logging into user account.

The previous kernel, kernel 4.15.0-43 does not have this issue, everything works fine, can re-arrange displays, hot dock and undock, close lid to use only external displays, soft reboot and system does not hang up or lock.

[Barton Janes (bcjanes)]

package linux-image-4.15.0-45-generic appears to have resolved this issue. I will follow up after further testing.

[Barton Janes (bcjanes)]

This has definitely been resolved with linux-image-4.15.0-45-generic. Reboots, hot dock / undock, changing the displays in system prefs, etc no longer lock the laptop up.