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Re: Xubuntu 14.10 second seat screen lock not working / gets stuck


On 12/31/2014 08:13 PM, Schlomo Schapiro wrote:
> Hi,
> see https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1406834

Looks like you have two problems that I'm guessing are unrelated:

  * Scenario #1:  When using xscreensaver, locking works but LightDM
    keeps trying and failing to spawn a greeter on non-seat0 seats
    while the screen is in power-save mode.
  * Scenario #2:  When using light-locker, locking on non-seat0 seats
    doesn't properly session-switch to LightDM.

You filed a bug report for scenario #1; would you please also file a bug
report for scenario #2 (against light-locker)?

> On 1 January 2015 at 01:34, Richard Hansen <ubuntu-a7x@xxxxxxxxxxxxxxx>
> wrote:
>> Support for session switching on non-seat0 seats was added in systemd
>> 208 [1] and xorg-server 1.16 [2], both of which are available in utopic
>> (but not trusty).
>> [1] http://cgit.freedesktop.org/systemd/systemd/commit/?id=d7bd01b547bd91353513131561de9cc7d9f7d405
>> [2] http://cgit.freedesktop.org/xorg/xserver/commit/?id=cac39219898f5e5a59ff8d8d6524f5fe0d111469
> ​Very very cool. So now I found out that it does not work for me.

I should mention that I have never tried utopic (I'm still running
trusty) so I don't know if session switching on non-seat0 seats would
work for me either.

> The question is why. I guess I'll try also with different graphics cards
> to find out if it is related to the radeon driver.

By "radeon driver" I assume you mean the open source radeon driver and
not the proprietary fglrx driver, right?

>>> It seems to me rather that light-locker just locks the session with the
>>> "This session is locked" but then lightdm cannot show the greeter
>>> anywhere to ask for a passwort to unlock it.
>> Yes; seems like something is trying to switch sessions but failing
>> somehow.  Anything interesting in lightdm or X logs?
> ​Yes, see above bug report. lightdm.log is now 1.4 GB after just a few
> hours...

What about scenario #2 (using light-locker)?

>>> and that after logging out
>>> of the session there is no new login screen. Apparently lightdm does not
>>> start a new session on this seat after the first session is done.
>> That seems odd to me, and sounds like a lightdm bug...  Do the lightdm
>> logs show anything interesting?
> ​Yes, it fails to start another X server. I guess that in my case (using
> xscreensaver instead of light-locker), I would expect this not to happen
> unless it is doing it in order to offer another login for user switching.

Whenever you log out, the X server is supposed to exit -- that's normal
behavior.  The display manager (LightDM) is then supposed to spawn a new
X instance.

What happens when you set allow-user-switching=false, switch to
light-locker, log in to seat-1, then log out?  Does it still fail?  What
are the symptoms exactly?  Anything interesting in the logs?

>> But it should, given that utopic should support session switching on
>> non-seat0 seats.  I would expect trusty to have problems, but not utopic.
> ​I see. Against which package(s) should I report this as a bug?


> Is this an "official" feature of utopic?

I don't know if any Ubuntu release has any "official" features, but
certainly there are some features Canonical cares more about than
others.  I don't think multiseat is high on their list of priorities.

However, session switching on non-seat0 seats is a feature of logind
v208 and X server v1.16, and those are in utopic, so if it's not working
then it's a bug in utopic that should be addressed.  And it will be
addressed if there's enough manpower to troubleshoot, fix, and test
(which is where volunteers like us come in).


>>> My workaround is now to use xscreensaver instead of light-locker. Works
>>> but ugly and much less integrated.
>> Good to know that there is a workaround.
> ​Well, it is not good enough since lightdm.log starts to fill up really
> fast. So I need to find another way, preferably with lightdm.
>> I believe linux-kvm supports multiple graphics and input devices, though
>> I have never tried it.
> ​Cool, will look into that too.
> Kind Regards,
> Schlomo

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