Cannot log in on unity with nvidia drivers

[fcole90]

After a recent update, it's no more possible to log in to Ubuntu 16.04 when using lightdm to access to Unity.

If I try to login lightdm disappears as if it was loading Unity, but after a few seconds the login prompt appears again.

### Workaround ###

Current workaround has been to purge all nvidia drivers, as nvidia-352 was installed.

The same driver (nvidia-352) works correctly in trusty, and until recently it used to work even on xenial.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xorg 1:7.7+13ubuntu1
ProcVersionSignature: Ubuntu 4.3.0-7.18-generic 4.3.3
Uname: Linux 4.3.0-7-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.19.4-0ubuntu2
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 Feb 9 20:11:26 2016
DistUpgraded: Fresh install
DistroCodename: xenial
DistroVariant: ubuntu
DkmsStatus:
 bbswitch, 0.8, 4.3.0-5-generic, x86_64: installed
 bbswitch, 0.8, 4.3.0-7-generic, x86_64: installed
 bbswitch, 0.8, 4.4.0-2-generic, x86_64: installed
 psmouse-focaltech, 0.1, 3.19.0-18-generic, x86_64: installed
 psmouse-focaltech, 0.1, 3.19.0-20-generic, x86_64: installed
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation 4th Gen Core Processor Integrated Graphics Controller [8086:0416] (rev 06) (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. 4th Gen Core Processor Integrated Graphics Controller [1043:178d]
InstallationDate: Installed on 2015-03-21 (325 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150321)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 003: ID 0bda:57b4 Realtek Semiconductor Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: ASUSTeK COMPUTER INC. X550JK
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.3.0-7-generic.efi.signed root=UUID=3eab3ace-7b67-4e6a-aea7-d31b73cc4819 ro quiet splash acpi_osi=
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/08/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: X550JK.303
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: X550JK
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrX550JK.303:bd10/08/2014:svnASUSTeKCOMPUTERINC.:pnX550JK:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnX550JK:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.name: X550JK
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.
version.compiz: compiz 1:0.9.12.2+16.04.20151211-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.66-2
version.libgl1-mesa-dri: libgl1-mesa-dri 11.1.1-1ubuntu2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.1.1-1ubuntu2
version.xserver-xorg-core: xserver-xorg-core 2:1.17.3-2ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.2-1ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.6.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160127-1ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1
xserver.bootTime: Tue Feb 9 19:54:16 2016
xserver.configfile: default
xserver.errors: systemd-logind: failed to get session: PID 926 does not belong to any known session
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 1117
 vendor LGD
xserver.version: 2:1.17.3-2ubuntu2

[fcole90 (fcole90)]

This bug is a duplicate of https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1543458, but I'm closing it as this contains useful debugging infos.