Double login to switch back to my session after closing the guest session

Thanks for your report; I made the same observation.

The log shows LightDM doing the correct thing - it unlocks the logind session when you get to the greeter. I suspect that Unity has regressed and is not removing its lock screen when this occurs.

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

copying debug info from IRC

"the enviroment variable XDG_SESSION_ID is not set anymore, that's the problem, we're not listening to the correct dbus path"

seems to be another fallover from the systemd user session transition

The reason is that (user) D-Bus and (user) systemd services don't run in the session any more, as they apply to all sessions of that user. To illustrate, check "systemctl status" and compare the bits that are directly under user@1000.service (user-global services) vs. the bits that are in the logind session (session-XX.scope).

So right now these don't have a "native" XDG_SESSION_ID. The intention is that you don't assume XDG_SESSION_ID and a D-Bus object path, but you query logind for it:

$ busctl call org.freedesktop.login1 /org/freedesktop/login1 org.freedesktop.login1.Manager GetUser u `id -u`
o "/org/freedesktop/login1/user/_1000"
$ busctl get-property org.freedesktop.login1 /org/freedesktop/login1/user/_1000 org.freedesktop.login1.User Display
(so) "c1" "/org/freedesktop/login1/session/c1"

This is actually a lot more comfortable if you use libsystemd and sd_uid_get_display(), like in https://cgit.freedesktop.org/polkit/commit/?id=a68f5dfd76 .

As a hack we could poke that into the graphical session units without poking it into *all* user services (as it would be conceptually wrong for e. g. gvfs, keyring, or pulseaudio), e. g. in unity.service's ExecStartPre=. But I think it's actually not difficult to fix it the proper way.

Hello Hadrien, or anyone else affected,

Accepted unity into yakkety-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/unity/7.5.0+16.10.20161112-0ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

I have updated my 16.10 yakkety with proposed enabled. Now, unity version is 7.5.0+16.10.20161112-0ubuntu1
The bug is fixed for me.
Thank you!

I tested 7.5.0+16.10.20161112-0ubuntu1. The second login screen shows for a short moment but then it disappears automatically after a fraction of second and I am back in my session.

This bug was fixed in the package unity - 7.5.0+16.10.20161112-0ubuntu1

---------------
unity (7.5.0+16.10.20161112-0ubuntu1) yakkety; urgency=medium

  [ Marco Trevisan (Treviño) ]
  * LockScreenController: ignore icon_paths_changed signal in
    menumanager for Lockscreen (LP: #1635625)

  [ Andrea Azzarone ]
  * Properly handle the file manager copy dialog in
    FileManagerLauncherIcon and in StorageLauncherIcon. (LP: #1575452,
    LP: #1609845)
  * Correctly position the force quit dialog when scaling is different
    than 1.0 (LP: #1637991)
  * GnomeSession: Retrieve the session id using dbus if $XDG_SESSION_ID
    is not set (LP: #1633749)

 -- Marco Trevisan (Treviño) <mail@3v1n0.net> Sat, 12 Nov 2016 02:13:01 +0000

The verification of the Stable Release Update for unity has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.