Monitor intermittently turns off and back on again

[Daniel]

I'm experiencing an issue after upgrading from Xubuntu 15.10 to 16.04. I'm using a Dell Latitude E7450, attached to a docking station, and connected to two Dell U2715H via mDP, both displaying 2560x1440.
Each of the displays intermittently turns off for about 2 or 3 seconds, and then turns back on again. I couldn't tell whether this behaviour is specifically triggered by anything - it seems to happen randomly. There is no notification from the screen's OSD when it goes black.
The issue does not occur when the system is booted with the previously installed kernel, 4.2.0-35-generic.

Please let me know if you need any further information.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-21-generic 4.4.0-21.37
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: dkozar 1793 F.... pulseaudio
 /dev/snd/controlC0: dkozar 1793 F.... pulseaudio
CurrentDesktop: XFCE
Date: Fri Apr 29 11:57:51 2016
InstallationDate: Installed on 2015-10-28 (184 days ago)
InstallationMedia: Xubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
MachineType: Dell Inc. Latitude E7450
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-21-generic.efi.signed root=UUID=4dc74fbd-1097-4419-a15f-7dbac52da6e0 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-21-generic N/A
 linux-backports-modules-4.4.0-21-generic N/A
 linux-firmware 1.157
SourcePackage: linux
UpgradeStatus: Upgraded to xenial on 2016-04-29 (0 days ago)
dmi.bios.date: 09/01/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A07
dmi.board.name: 0Y15C1
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA07:bd09/01/2015:svnDellInc.:pnLatitudeE7450:pvr:rvnDellInc.:rn0Y15C1:rvr:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E7450
dmi.sys.vendor: Dell Inc.

[Brad Figg (brad-figg)]

This change was made by a bot.

[Hugh Wells (winxp0922)]

I have this problem too on both a Thinkpad T410 and T450s. Never happened before I upgraded to 16.04

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.6 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.6-rc6-wily/

[Daniel (dkk089)]

Thanks for the suggestion. I tested latest v4.6 kernel (4.6.0-040600rc6-generic) successfully. I haven't seen the issue pop up in the last 7 hours or so, so it does indeed seem that this was fixed upstream.

[penalvch (penalvch)]

Daniel, the next step is to fully reverse commit bisect from kernel 4.4 to 4.6-rc6 in order to identify the last bad commit, followed immediately by the first good one. Once this good commit has been identified, it may be reviewed for backporting. Could you please do this following https://wiki.ubuntu.com/Kernel/KernelBisection#How_do_I_reverse_bisect_the_upstream_kernel.3F ?

Please note, finding adjacent kernel versions is not fully commit bisecting.

After the fix commit (not kernel version) has been identified, then please mark this report Status Confirmed.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]