Bug#702918: kdm: Kdm can't start KDE sessions twice.

[Pino Toscano]

reopen 702918
tags 702918 = confirmed
severity 702918 important
retitle 702918 kwin with effects hangs (with 100% CPU) on second kdm login
reassign 702918 nvidia-glx
affects 702918 kde-window-manager kdm
thanks

Hi,

Alle mercoledì 13 marzo 2013, José Luis Feliciano Triana García ha scritto:
> You login first time OK, then you log off, after you retype your
> password, and the session is not able to start, I can hear the KDE
> sound at login, but no change in the screen as the splash screen
> keeps frozen.
> I log on on a tty, open top, and then Kwin is in the top, consuming
> the 90-100 % of cpu time.
> 
>  I tried to use the privative drivers (nvidia) with no result, I
> changed KDM to LightDM, and with lightDM I can start KDE sessions
> twice, but not with KDM as display manager.
> 
> Steps to reproduce:
> 
> With KDM:
> 
> 1) Start a KDE session.
> 2) Log off  from that KDE session.
> 3) Login into a KDE session again.
> 4) Vuala! splash screen frozen, KDE sound session, but no desktop.
> 5) Restart X server (I had to activate the ctrl + alt + return
> binding in order to kill Xserver), alternatively you can restar the
> X server in kdm, and it will allow you to login as well.
> 6) Logon to the KDE session again and you will be able to login (no
> splash screen frozen)
> 
> It is expected to run a KDE session twice.
> 
> Additional information:
> 
> I installed Openbox, I can start a pure Openbox session twice and a
> KDE Openbox session as well, but not a KDE/Kwin session.
> 
> While I have the splash screen frozen, In a tty using top I can see
> that Kwin is consuming an unusual amount of CPU time, and the
> process becomes unresponsive, I can't kill it through top, I must
> restart the whole X server in order to stop Kwin consuming most cpu.
> 
> I changed the configuration of kdm, the theme through systemsettings
> , but even before I made any change, I had this behavior using Kdm.
> 
> I actually use lightDM, as it allows me to start KDE sessions twice
> in a row, the times I may need to.
> 
> This only happens per user, I explain I have my user "foo" and I
> create another user "bar".
> 
> I login with foo, then I log out (no user switch), I login with bar,
> no problem, I logout bar session, then I try to login a second time
> with foo, splash screen frozen, restart X server, and I able to log
> in a second time as foo.

I can reproduce the issue too, on wheezy/i386 and current nvidia
drivers; it seems this happens only when the desktop effects are
enabled.

I tried to get a backtrace of kwin when it starts to use the whole CPU;
I get nothing meaningful (even with all the -dbg packages installed),
if not thread traces ending on libGL calls. I am not sure though, why
this happens only with kdm (which should have no businness in
compositing stuff).

For now, I'm reassigning to nvidia-glx; nvidia people, feel free to
share your thoughts.

-- 
Pino Toscano
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