Returning to existing session is unreliable and can leave on blank screen

Acer S7 - Intel Haswell Laptop with Intel GPU using i915 driver.

The same behavior can be replicated by letting the screen lock itself due to idle, or by locking your workstation.

Status changed to 'Confirmed' because the bug affects multiple users.

See this on desktop with nvidia.

Note:

lock then unlock
see cursor flashing in corner of vt8

Playing music prior to locking - muic muted (as expected)
When trying to unlock music can be momentarily heard until lock screen shows again

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1656399

Downgraded lightdm packages as follows:

1.21.1-0ubuntu1 locking works suspend works

1.21.1-0ubuntu2 locking works suspend works

1.21.2-0ubuntu not downloadable

1.21.3-0ubuntu1 no locking

however - seems locking fails in vm with 1.21.1-0ubuntu2

attached lightdm.log following failure to unlock

Status changed to 'Confirmed' because the bug affects multiple users.

affects lubuntu

Error in comment #7

1.21.1-0ubuntu2 does not allow locking

The change in there is:

  Restore patch from 1.20.0-0ubuntu3:
  * Add debian/patches/terminate-session.patch: Terminate leftover processes
    in greeter session. It can happen that the greeter session does not
    properly clean up itself on logout. This causes leaked processes like
    settings-daemon which act on the user session as they share the same
    $DISPLAY. Ask logind to terminate remaining processes in the greeter
    session on closing, which is more robust than trying to fix every greeter.
    (LP: #1637758)

 -- Martin Pitt <email address hidden> Tue, 22 Nov 2016 09:43:39 +0100

Which suggests that the issue might be lightdm-gtk-greeter being killed before the unlock has completed?

Actually the relevant part of the lightdm.log is:

[+7580.55s] DEBUG: Seat seat0: Returning to existing user session wolf
[+7580.55s] DEBUG: Unlocking login1 session c2
[+7580.55s] DEBUG: Activating VT 7
[+7580.67s] DEBUG: Seat seat0: Stopping greeter
[+7580.67s] DEBUG: Terminating login1 session c6
[+7580.69s] DEBUG: Session pid=13835: Sending SIGTERM
[+7580.69s] DEBUG: Activating login1 session c2
[+7580.70s] WARNING: Failed to flush data to greeter: Broken pipe
[+7580.70s] DEBUG: Greeter closed communication channel
[+7580.70s] DEBUG: Session pid=13835: Terminated with signal 1

Which suggests the greeter is not exiting cleanly. This suggests:
- The change to the method by which lightdm kills the greeter might not be handled well by lightdm-gtk-greeter.
- There's probably a bug in lightdm in that it asked the greeter to quit, so it shouldn't care if it doesn't exit cleanly in this case.
- We need the greeter log to know more about what happened there.

Greeter log

Checked with gnome-screensaver and xscreensaver instead of light-locker.

In both cases -

lock and suspend both work as expected.

lock then login as new user fails to allow you back to original use

downgrading lightdm to 1.21.1-0ubuntu1 allows lock and login as new user, however both require user to login twice to gain access to locked desktop

was going to check the budgie greeter - but that uses lightdm-gtk-greeter and fails the same as with other flavours

This bug seems to affect Lubuntu Zesty alpha 2. It affects all Lubuntu test cases.

It turns out I can reproduce this with unity-greeter (on zesty). I get the following:
1. Log into session from greeter
2. Switch to greeter and log in again
(returned to session)
3. Switch to greeter and log in again
Switched to black screen, can manually VT switch back to session but need to unlock it from screen locker.
4. Switch to greeter and log in again
Returned to session, but screen locker shown.

There were a couple of bugs regarding signals and return values from greeters which I have fixed in lp:lightdm, but these don't seem to have caused the issue.

Still investigating...

It happens to me, too.
======================
Something (big) cropped up. When I returned to my NetBook, the screen had locked. Typed my password in. System then (visually) unlocked itself, paused briefly and then locked me back out again. You can test this more quickly by using the keyboard shortcut of CTRL+ALT+l

Naturally I thought I'd got the password wrong. Tried typing in the password in upper case and it didn't do the above - it gave a red error message, pretty much expected.

The only way I could get into a locked system again was to chose a "Shutdown" menu option.

Played around with it for a bit. Managed to unlock the NetBook successfully once - then it resumed its unhelpful behaviour.

And here are my system's details.
=================================
On 28 January 2017 at 02:55, Simon Quigley <email address hidden> wrote:

    Lubuntu Zesty Zapus Alpha 2 (soon to be 17.04) has been released!

OK. Used your link and downloaded MD5SUMS and zesty-desktop-i386.iso. Ran md5sum and it checked out OK:-
1c3f420bb80754bc3b31eb479d77e3b5 zesty-desktop-i386.iso

Used Startup Disc Creator on a 4GB USB flash drive.

Hardware used to install iso on:

Samsung NC10 - hawking
Intel Atom N270, 1.66GHz, 32-bit, 2GiB RAM, 149.05 GiB hard drive, no optical drive, Ethernet and WiFi connections
Full details see here:- https://gist.github.com/21b61903871ee685fc79

Booted install media without Ethernet cable connected. Had to reboot system after connecting Ethernet cable before it was happy to continue the update. Opted for "Download updates while installing Lubuntu" and "Install third-party software". Chose option to wipe hard drive and install Lubuntu on top of it. Put in a hostname of "hawking" for this NetBook. Installer said there was already another system on the network called "hawking". Decided not to argue so named the system "hawking2".

Install completed successfully and asked for the (installation) storage medium at a suitable time.

Rebooted system, logged in. The start/swift menu icon isn't present. Ran Software Updater OK. Saw an email on lubuntu-devel complaining about Firefox not working. On my NetBook, ran Firefox (version 50.1.0) ran fine and I Googled "Hello World".

Normally I only use the "alternate" iso images and in the install I repartition the hard drive manually. For some reason I did it a little differently this time :)

This is effecting me on Xubuntu 17.04

Intel Skylake i7 with HD530 Graphics (Lenovo Thninkpad T460s)

really wish people wouldn't fiddle with bug status

On 2017-02-20 08:27, flocculant wrote:
> really wish people wouldn't fiddle with bug status

Reversed the latest change.

@Gunnar - thank you

@robert - I've seen reports from xubuntu testers where it was sometimes working. So I tried more on a completely brand new installation.

Lock - unlock fails - this continued for 3 attempts at which point I reached desktop.
Lock and unlock cycle next time took 2 attempts.
Lock and unlock cycle next time took 1 attempt.

I was then able to lock and unlock at will.

Attached all /var/log/lightdm logs from that session.

In my used and abused installation I see similar behaviour.

Same experience on my updated Lubuntu 17.04.

I'm also finding it to be unreliable. It seems to be a race condition between the greeter quitting and the session starting. I suspect the use of logind has made this race more likely.

Robert, any chance we can get this fix in Zesty Archive in debian/patches? I can help with packaging if needed (if you aren't working on it already).

Uploaded to zesty as 1.21.5-0ubuntu1.

The change fixes the issue for me, though of course it may not be the only issue affecting screen locking with light-locker (as per the original bug description). If you continue to have problems please comment here an open a new bug and we'll tackle further issues there. Thanks for all the great feedback in this bug!

@ Robert - grabbed from -proposed.

Locking from desktop appears to work as expected.

Unlocking from suspend - I get hiccups if I'm a bit quick entering password (bug 1666803)

Installing 1.21.5-0ubuntu1 has solved the problem coming out from lock screen

This bug was fixed in the package lightdm - 1.21.5-0ubuntu1

---------------
lightdm (1.21.5-0ubuntu1) zesty; urgency=medium

  * New upstream release:
    - Fix logic that checked if a session was being stopped.
      This fixes a race condition that could cause logging into an existing
      session from a greeter to not return to that session. (LP: #1656399)

 -- Robert Ancell <email address hidden> Wed, 22 Feb 2017 12:38:50 +1300

The new version has fixed the issue for me!