Recently I encountered this problem and discovered a solution. I posted my solution at:
kubuntu 16.04 SDDM login screen hangs https://askubuntu.com/questions/765364/kubuntu-16-04-sddm-login-screen-hangs/874972#874972 For completeness sake, I will also repost the solution here. ---------- Recently I encountered this problem with kubuntu 16.04 SDDM login screen hangs. The issue occurred after I installed kubuntu 16.04 on an Intel i7-7700k with Intel 630 HD graphics and then updated to the latest packages. I was able to login using the workaround of using Ctrl+Alt+F1 to get to a text console and then Ctrl+Alt+F7 to get back to X and the logged in session. I stumbled upon a fix to the login hang while I was working to get rid of a screen tearing problem. The fix involves changing the compositor rendering backend from XRender to OpenGL. More specifically to address the hang on login and problem with screen tearing I did the following: FIX SCREEN TEARING AND LOGIN HANGING ------------------------------------ A) Start K -> Settings -> System Settings Under Hardware section Double-click Display and Monitor Choose Compositor on LHS Enable compositor on startup: Checked # was checked Rendering backend: OpenGL 3.1 # was XRender OpenGL interface: GLX Tearing prevention ("vsync"): Full screen repaints # was Automatic Ignore message "Full screen repaints" can cause performance problems. Click Apply REFERENCES: Bug 321589 - Automatic VSync strategy causes tearing https://bugs.kde.org/show_bug.cgi?id=321589 Screen Tearing on Kubuntu 16.04 with Intel Drivers? https://askubuntu.com/questions/764302/screen-tearing-on-kubuntu-16-04-with-intel-drivers B) Set KWIN variables. Edit /etc/environment and add the top and bottom line: __GL_YIELD="USLEEP" #KWIN_TRIPLE_BUFFER=0 KWIN_USE_BUFFER_AGE=0 REFERENCES: https://community.kde.org/KWin/Environment_Variables https://askubuntu.com/questions/764302/screen-tearing-on-kubuntu-16-04-with-intel-drivers/774788 Listed as also working with NVidia. I hope the above steps help others get rid of the login hang and screen tearing problems. ** Bug watch added: KDE Bug Tracking System #321589 https://bugs.kde.org/show_bug.cgi?id=321589 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1623969 Title: Cannot log in to kubuntu after update (Intel graphics + ksshaskpass) Status in xorg package in Ubuntu: Invalid Bug description: I just took some updates to a number of graphic libraries on 16.04, and now I can't login to kubuntu. The symptom is that it takes my password on the greeter screen, but never updates the screen after that. The messages include these possibly related kernel messages: kernel: [ 701.564034] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* uncleared fifo underrun on pipe B kernel: [ 701.564054] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun I'm currently running kernel 4.4.0-36. Here are my most recent updates. The problem started after I rebooted. Of course that was the next time I logged in too... Start-Date: 2016-09-07 08:46:04 Commandline: /usr/bin/unattended-upgrade Remove: libcdaudio1:amd64 (0.99.12p2-14), linux-image-extra-4.2.0-36-generic:amd64 (4.2.0-36.42), linux-image-extra-4.4.0-22-generic:amd64 (4.4.0-22.40), gtk2-engines-murrine:amd64 (0.98.2-0ubuntu2.1), linux-image-extra-4.4.0-24-generic:amd64 (4.4.0-24.43), libslv2-9:amd64 (0.6.6+dfsg1-3build1), linux-image-extra-4.4.0-28-generic:amd64 (4.4.0-28.47), linux-image-extra-4.4.0-31-generic:amd64 (4.4.0-31.50), libfaac0:amd64 (1.28+cvs20151130-1) End-Date: 2016-09-07 08:48:13 Start-Date: 2016-09-07 16:42:27 Install: libgnome-keyring-common:amd64 (3.12.0-1build1, automatic), libgnome-keyring0:amd64 (3.12.0-1build1, automatic) Upgrade: libgles2-mesa:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libgles1-mesa:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libglapi-mesa:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libglapi-mesa:i386 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), p11-kit:amd64 (0.23.2-3, 0.23.2-5~ubuntu16.04.1), libxatracker2:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libegl1-mesa-drivers:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libegl1-mesa:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libegl1-mesa:i386 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), p11-kit-modules:amd64 (0.23.2-3, 0.23.2-5~ubuntu16.04.1), libgbm1:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libgbm1:i386 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), cups-filters:amd64 (1.8.3-2ubuntu3, 1.8.3-2ubuntu3.1), chromium-browser:amd64 (51.0.2704.79-0ubuntu0.16.04.1.1242, 52.0.2743.116-0ubuntu0.16.04.1.1250), libcupsfilters1:amd64 (1.8.3-2ubuntu3, 1.8.3-2ubuntu3.1), chromium-codecs-ffmpeg-extra:amd64 (51.0.2704.79-0ubuntu0.16.04.1.1242, 52.0.2 743.116-0ubuntu0.16.04.1.1250), libwayland-egl1-mesa:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libfontembed1:amd64 (1.8.3-2ubuntu3, 1.8.3-2ubuntu3.1), libgl1-mesa-dri:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libgl1-mesa-dri:i386 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), cups-filters-core-drivers:amd64 (1.8.3-2ubuntu3, 1.8.3-2ubuntu3.1), libgl1-mesa-glx:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libgl1-mesa-glx:i386 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), libp11-kit0:amd64 (0.23.2-3, 0.23.2-5~ubuntu16.04.1), libp11-kit0:i386 (0.23.2-3, 0.23.2-5~ubuntu16.04.1), mesa-vdpau-drivers:amd64 (11.2.0-1ubuntu2.1, 11.2.0-1ubuntu2.2), chromium-browser-l10n:amd64 (51.0.2704.79-0ubuntu0.16.04.1.1242, 52.0.2743.116-0ubuntu0.16.04.1.1250), ubuntu-mono:amd64 (14.04+16.04.20160621-0ubuntu1, 14.04+16.04.20160804-0ubuntu1), cups-browsed:amd64 (1.8.3-2ubuntu3, 1.8.3-2ubuntu3.1) End-Date: 2016-09-07 16:44:34 Start-Date: 2016-09-12 14:31:39 Commandline: /usr/sbin/synaptic Requested-By: alanr (1000) Upgrade: snapd:amd64 (2.13, 2.14.2~16.04), libappstream-glib8:amd64 (0.5.13-1ubuntu2, 0.5.13-1ubuntu3), neo4j:amd64 (3.0.4, 3.0.5), accountsservice:amd64 (0.6.40-2ubuntu11.1, 0.6.40-2ubuntu11.2), libaccountsservice0:amd64 (0.6.40-2ubuntu11.1, 0.6.40-2ubuntu11.2) End-Date: 2016-09-12 14:32:17 It was after rebooting after updates that this occurred. My workaround is "rm -fr ~/.kde" - and that allows me to log in. I'm crippled, but at least I can log in... If I try to log in again without doing this, the problem recurs. This happens even if I just log in and log back out, and try to log in again. However, I may just found a better workaround - press ALT-CTRL-F1 then ALT-CTRL-F7, and then the next chunk of the login sequence occurs. This makes it consistent with an issue reported in AskUbuntu http://askubuntu.com/questions/765364/kubuntu-16-04-sddm-login-screen- hangs And it's possibly related to bug https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1550779 - because of the CPU underrun being apparently related to graphics. In fact, each time I do this, I get a little further in the login sequence. It appears that the trigger for this bug is likely the prompts to provide passwords for my various ssh private keys (I have four). This also includes prompts from the KDE wallet manager for me to use the KDE wallet - and I don't use that feature. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: xorg 1:7.7+13ubuntu3 ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16 Uname: Linux 4.4.0-36-generic x86_64 ApportVersion: 2.20.1-0ubuntu2.1 Architecture: amd64 CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' Date: Thu Sep 15 07:53:07 2016 DistUpgraded: 2016-05-25 14:07:14,644 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py' DistroCodename: xenial DistroVariant: ubuntu ExtraDebuggingInterest: Yes GraphicsCard: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller [8086:0412] (rev 06) (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller [1043:8534] InstallationDate: Installed on 2014-07-12 (795 days ago) InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1) MachineType: ASUS All Series ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-36-generic root=UUID=1b9b0c50-d4ac-471c-a09a-0ee1cad092e4 ro quiet splash vt.handoff=7 SourcePackage: xorg UpgradeStatus: Upgraded to xenial on 2016-05-25 (112 days ago) dmi.bios.date: 01/16/2014 dmi.bios.vendor: ASUSTeK COMPUTER INC. (Licensed from AMI) dmi.bios.version: 1707 dmi.board.asset.tag: To be filled by O.E.M. dmi.board.name: P9D WS dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: Rev 1.xx dmi.chassis.asset.tag: Asset-1234567890 dmi.chassis.type: 3 dmi.chassis.vendor: Chassis Manufacture dmi.chassis.version: Chassis Version dmi.modalias: dmi:bvnASUSTeKCOMPUTERINC.(LicensedfromAMI):bvr1707:bd01/16/2014:svnASUS:pnAllSeries:pvrSystemVersion:rvnASUSTeKCOMPUTERINC.:rnP9DWS:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion: dmi.product.name: All Series dmi.product.version: System Version dmi.sys.vendor: ASUS version.compiz: compiz N/A version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.67-1ubuntu0.16.04.2 version.libgl1-mesa-dri: libgl1-mesa-dri 11.2.0-1ubuntu2.2 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 11.2.0-1ubuntu2.2 version.xserver-xorg-core: xserver-xorg-core 2:1.18.3-1ubuntu2.3 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.0-1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160325-1ubuntu1.1 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1build2 xserver.bootTime: Thu Sep 15 07:51:50 2016 xserver.configfile: default xserver.errors: xserver.logfile: /var/log/Xorg.0.log xserver.outputs: product id 9393 vendor ACI xserver.version: 2:1.18.3-1ubuntu2.3 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1623969/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
