Bug#800938: Bug#799948: Plasma desktop is unable to start (black screen - panic)

[Luca Boccassi]

On Tue, 2015-10-20 at 12:16 +0300, Vladimir Stavrinov wrote:
> On Mon, Oct 19, 2015 at 10:11:45PM +0100, Luca Boccassi wrote:
> 
> > Maybe there's some context I'm missing. Forgive me for asking, but are
> > you sure this is due to the Nvidia driver packages or glx-alternatives?
> 
> Absolutely. This is Nvidia driver problem. Few days ago I conducted
> specific experiment. After upgrading to latest version of all nvidia
> and glx packages, I've downgraded only kernel module and after
> reloading module the glx got working. But after rebooting system the
> problem returned again. So not only kernel module is problem, but it
> is main.

That is most likely because the permissions on the device nodes are
different when you load the module manually vs when udev does it at
boot.

> > Andreas, you use KDE if I'm not mistaken. Are you seeing any issues? Do
> 
> How many times again: this is not problem of KDE, plasma, kodi or any
> other software using glx. This is problem of glx in nvidia driver. 
> 
> I am using xlock from very old package xlockmore-gl not included in
> any of today's debian distributions. But it has two options
> "-modelist allgl" and "-modelist all-allgl". First is for include glx
> modes, second - to exclude ones. This is very good for testing glx,
> because it explicitly points to glx as the source of problem when it
> works with second option and doesn't work with the first one.
> 
> So it is certainly clear, that the source of our problems is glx
> feature of nvdia driver. But the fact that You can't reproduce the
> problem (if You can't, because You never mentioned this) may mean,
> that problem is somehow hardware specific. In this case there are no
> way to debug it as to ask us to do for You some experiments of Your
> choice.
> 
> Here is my hardware:
> 
> lspci | grep -i nvidia
> 01:00.0 VGA compatible controller: NVIDIA Corporation GK208 [GeForce GT 635] (rev a1)
> 01:00.1 Audio device: NVIDIA Corporation GK208 HDMI/DP Audio Controller (rev a1)
> 
> If this guess is not true and the problem is not hardware specific, then You
> should try number of different software using glx to reproduce the
> problem.
> 
> And finally it is possible, that at some point of investigation You
> will understand necessity to escalate the problem to upstream.

The reason I'm asking about which DM this is happening on is because,
after applying the video group workaround I am not experiencing any
issues with any software that uses GLX or any other library provided by
the nvidia drivers. So, I was just trying to narrow it down and get the
full picture of the environment.

As I wrote earlier, yesterday I noticed that it is not enough for the
desktop-manager user (sddm or Debian-gdm) to be in the video group, the
user also MUST be part of it, otherwise GDM breaks due to the device
nodes permissions problem.

Could you please make sure that both your user and your DM user (sddm I
believe?) are in the video group and try again and report the result?

Kind regards,
Luca Boccassi
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