On waking from, generally a long sleep, my laptop loops in gdm. I get a continuous stream of:
Nov 20 15:34:15 X1 /usr/lib/gdm3/gdm-x-session[2674]: (--) modeset(0): HDMI max TMDS frequency 310000KHz
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): EDID vendor "HPN", prod id 13450
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Using hsync ranges from config file
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Using vrefresh ranges from config file
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Printing DDC gathered Modelines:
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "2560x1440"x0.0 241.50 2560 2608 2640 2720 1440 1443 1448 1481 +hsync -vsync (88.8 kHz eP)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080"x0.0 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync (67.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080"x0.0 148.35 1920 1936 1980 2640 1080 1084 1089 1125 +hsync +vsync (56.2 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1280x720"x0.0 74.25 1280 1390 1430 1650 720 725 730 750 +hsync +vsync (45.0 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "2560x1440"x0.0 304.25 2560 2608 2640 2720 1440 1443 1448 1492 +hsync -vsync (111.9 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "800x600"x0.0 40.00 800 840 968 1056 600 601 605 628 +hsync +vsync (37.9 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "640x480"x0.0 31.50 640 656 720 840 480 481 484 500 -hsync -vsync (37.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "640x480"x0.0 25.18 640 656 752 800 480 490 492 525 -hsync -vsync (31.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "720x400"x0.0 28.32 720 738 846 900 400 412 414 449 -hsync +vsync (31.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1280x1024"x0.0 135.00 1280 1296 1440 1688 1024 1025 1028 1066 +hsync +vsync (80.0 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1024x768"x0.0 78.75 1024 1040 1136 1312 768 769 772 800 +hsync +vsync (60.0 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1024x768"x0.0 65.00 1024 1048 1184 1344 768 771 777 806 -hsync -vsync (48.4 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "800x600"x0.0 49.50 800 816 896 1056 600 601 604 625 +hsync +vsync (46.9 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080"x60.0 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -hsync +vsync (67.1 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1600x900"x60.0 119.00 1600 1696 1864 2128 900 901 904 932 -hsync +vsync (55.9 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1280x720"x60.0 74.48 1280 1336 1472 1664 720 721 724 746 -hsync +vsync (44.8 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1200"x0.0 154.00 1920 1968 2000 2080 1200 1203 1209 1235 +hsync -vsync (74.0 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1680x1050"x0.0 119.00 1680 1728 1760 1840 1050 1053 1059 1080 +hsync -vsync (64.7 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1440x900"x0.0 88.75 1440 1488 1520 1600 900 903 909 926 +hsync -vsync (55.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1280x800"x0.0 71.00 1280 1328 1360 1440 800 803 809 823 +hsync -vsync (49.3 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1280x1024"x0.0 108.00 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync (64.0 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080"x0.0 148.50 1920 2448 2492 2640 1080 1084 1089 1125 +hsync +vsync (56.2 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1280x720"x0.0 74.25 1280 1720 1760 1980 720 725 730 750 +hsync +vsync (37.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "720x480"x0.0 27.00 720 736 798 858 480 489 495 525 -hsync -vsync (31.5 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "720x576"x0.0 27.00 720 732 796 864 576 581 586 625 -hsync -vsync (31.2 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080i"x0.0 74.25 1920 2008 2052 2200 1080 1084 1094 1125 interlace +hsync +vsync (33.8 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1440x480i"x0.0 27.00 1440 1478 1602 1716 480 488 494 525 interlace -hsync -vsync (15.7 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080i"x0.0 74.25 1920 2448 2492 2640 1080 1084 1094 1125 interlace +hsync +vsync (28.1 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1440x576i"x0.0 27.00 1440 1464 1590 1728 576 580 586 625 interlace -hsync -vsync (15.6 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (II) modeset(0): Modeline "1920x1080"x0.0 74.25 1920 2558 2602 2750 1080 1084 1089 1125 +hsync +vsync (27.0 kHz e)
Nov 20 15:34:16 X1 /usr/lib/gdm3/gdm-x-session[2674]: (--) modeset(0): HDMI max TMDS frequency 310000KHz
Eventually it quiesces, but it generally takes about 10 minutes before the machine is usable.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.3 LTS
Release: 18.04
Codename: bionic
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gdm3 3.28.3-0ubuntu18.04.4
ProcVersionSignature: Ubuntu 4.15.0-70.79-generic 4.15.18
Uname: Linux 4.15.0-70-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
CurrentDesktop: XFCE
Date: Wed Nov 20 15:35:34 2019
InstallationDate: Installed on 2018-11-06 (379 days ago)
InstallationMedia: Ubuntu-Server 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_GB.UTF-8
SHELL=/bin/bash
SourcePackage: gdm3
UpgradeStatus: No upgrade log present (probably fresh install)