I have the same problem. See the attached syslog. The x-server almost crashes, and if I wait for a long time I might manage to get back to the login screen.
The problem seems to occur mainly in my case when using the Google Chrome browswer. I have an Nvidia card using KMS and Nouveau, and my network connection is via WiFi. I can confirm the problem is distro-inpependent, I use Gentoo Linux. ** Attachment added: "Syslog" https://bugs.launchpad.net/ubuntu/+source/libx11/+bug/1636564/+attachment/4900387/+files/syslog.txt -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to libx11 in Ubuntu. https://bugs.launchpad.net/bugs/1636564 Title: Segfault from libX11.so.6.3.0 Status in libx11 package in Ubuntu: Confirmed Bug description: Something went wrong with my Ubuntu 16.04 LTS desktop today. When I got back to the system Mattermost and a Chrome were indicating that the network was not working. I started to look about and it seemed that my main ethernet network connection had lost its IPv4 address somehow. ifconfig and the GUI network manager confirmed this. To try and resolve this I physically removed the connector and the plugged it back in. Shortly after I did this my GUI seemed to die out and I ended up back at the login screen. Once everything had calmed down I logged back in. After some digging about in the logs I noticed the following in /var/log/kern.log Oct 25 13:01:09 thorne-ul-dt kernel: [694321.877561] Mattermost[744]: segfault at 968 ip 00007f8a9e257643 sp 00007ffe72a3b510 error 4 in libX11.so.6.3.0[7f8a9e22f000+135000] Oct 25 13:01:09 thorne-ul-dt kernel: [694322.029362] chrome[745]: segfault at 968 ip 00007fd4b5c73643 sp 00007fff94f78d90 error 4 in libX11.so.6.3.0[7fd4b5c4b000+135000] That seemed to be the correct time for the problem I noticed. What exactly caused it I am not sure. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: libx11-6 2:1.6.3-1ubuntu2 ProcVersionSignature: Ubuntu 4.4.0-42.62-generic 4.4.21 Uname: Linux 4.4.0-42-generic x86_64 .tmp.unity_support_test.0: ApportVersion: 2.20.1-0ubuntu2.1 Architecture: amd64 CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CompositorRunning: compiz CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0' CompositorUnredirectFSW: true CurrentDesktop: Unity Date: Tue Oct 25 17:07:28 2016 DistUpgraded: Fresh install DistroCodename: xenial DistroVariant: ubuntu GraphicsCard: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller [8086:0412] (rev 06) (prog-if 00 [VGA controller]) Subsystem: Gigabyte Technology Co., Ltd Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller [1458:d000] InstallationDate: Installed on 2015-03-12 (592 days ago) InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1) MachineType: Gigabyte Technology Co., Ltd. H81M-DS2V ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-38-generic.efi.signed root=/dev/mapper/ubuntu--vg-root ro quiet splash crashkernel=384M-:128M vt.handoff=7 SourcePackage: libx11 UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 08/11/2015 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: F6 dmi.board.asset.tag: To be filled by O.E.M. dmi.board.name: H81M-DS2V dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: x.x dmi.chassis.asset.tag: To Be Filled By O.E.M. dmi.chassis.type: 3 dmi.chassis.vendor: Gigabyte Technology Co., Ltd. dmi.chassis.version: To Be Filled By O.E.M. dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF6:bd08/11/2015:svnGigabyteTechnologyCo.,Ltd.:pnH81M-DS2V:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rnH81M-DS2V:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.: dmi.product.name: H81M-DS2V dmi.product.version: To be filled by O.E.M. dmi.sys.vendor: Gigabyte Technology Co., Ltd. version.compiz: compiz 1:0.9.12.2+16.04.20160823-0ubuntu1 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 2:1.18.4-0ubuntu0.1 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: Tue Oct 25 13:01:04 2016 xserver.configfile: default xserver.errors: xserver.logfile: /var/log/Xorg.0.log xserver.outputs: product id 30926 vendor BNQ xserver.version: 2:1.18.4-0ubuntu0.1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libx11/+bug/1636564/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp