[SOLVED] Blank screen with visible cursor after unlocking

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[SOLVED] Blank screen with visible cursor after unlocking

Postby lufte » 2020-03-07 18:22

Fellow Debian users: I need help diagnosing an issue to be able to, at least, file a proper bug report.

Sometimes after unlocking my desktop I'm met by a blank screen with just a cursor. I can move the cursor and switch to another TTY, but that's about it. I fix it by restarting lightdm.

I had initially thought it was a bug in my locking app, light-locker, but I now replaced it with xfce4-screensaver and the bug still occurs. I have looked at X, lightdm and light-locker's logs but none of them show errors.

I appreciate any clue on where to look to diagnose the issue. It only happens after unlocking (not when logging in) and I'm running an up-to-date Debian testing with lightdm and Xfce.
Last edited by lufte on 2020-03-12 21:57, edited 1 time in total.
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Re: Blank screen with visible cursor after unlocking

Postby Head_on_a_Stick » 2020-03-07 19:21

Check the systemd journal and ~/.xsession-errors.

It sounds like your graphics drivers are bugging out, what are you using?

And if this is testing then it could just be a SNAFU. The development branches are like that sometimes. Users of testing are expected to be able to dig into such issues themselves, if you can't do that then stick to stable instead.
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Re: Blank screen with visible cursor after unlocking

Postby lufte » 2020-03-08 21:18

It sounds like your graphics drivers are bugging out, what are you using?

Ah, thanks, I was thinking this was related to the locker itself or maybe lightdm. It's a Thinkpad X230t with intel graphics. This is the output of lshw -c display:
Code: Select all
*-display                 
       description: VGA compatible controller
       product: 3rd Gen Core processor Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 09
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:32 memory:f0000000-f03fffff memory:e0000000-efffffff ioport:6000(size=64) memory:c0000-dffff

The driver is xserver-xorg-video-intel. I see nothing related to the error in systemd journal nor .xsession-errors, but apt sometimes complains about some "Possible missing firmware" for i915, so maybe that's related.
Users of testing are expected to be able to dig into such issues themselves

Yes, I know. I've been using testing for many years and that's usually the case, except when it comes to video or X. At least now I'm headed in the right direction. Thank you.
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Re: Blank screen with visible cursor after unlocking

Postby Head_on_a_Stick » 2020-03-09 15:04

lufte wrote:The driver is xserver-xorg-video-intel

Are you sure? I think bullseye defaults to the modesetting driver for Intel cards now. If it is running the Intel DDX driver then try swapping to the modesetting driver, or vice versa.
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Re: Blank screen with visible cursor after unlocking

Postby lufte » 2020-03-09 15:27

Yeah, I read in the package description that this driver is no longer recommended but I tried uninstalling it and X won't start. I assumed the other driver (modesetting?) was installed by default but maybe that's not the case. I will investigate this further and try using the driver you recommend.
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Re: Blank screen with visible cursor after unlocking

Postby Head_on_a_Stick » 2020-03-09 15:32

lufte wrote:I assumed the other driver (modesetting?) was installed by default but maybe that's not the case.

The modesetting DDX driver is provided by the xserver-xorg-core package, which should already be installed.

If X failed to start after you removed xserver-xorg-video-intel then check if you have any X.Org configuration files that may be attempting to force it. Otherwise check the X.Org log to see why it failed.

FWIW the modesetting driver can be used even with xserver-xorg-video-intel installed by creating a configuration file:
Code: Select all
# /etc/X11/xorg.conf.d/20-modesetting.conf
Section "Device"
   Identifier "Device0"
   Driver "modesetting"
EndSection

But make sure there isn't also a file calling the "intel" driver (as I mentioned above).
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Re: Blank screen with visible cursor after unlocking

Postby lufte » 2020-03-09 23:45

I did indeed have a configuration file which set the "intel" driver. I now removed that file, uninstalled the xserver-xorg-video-intel package, and X starts normally . I haven't been able to reproduce the issue although it was kind of random, so I'm going to give it some time, but maybe this was it.

Thank you for your help. I'll mark the issue as solved if the bug doesn't come up during the next days.
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