Screen restarts and logs out when disconnecting HDMI cable

[Anne Chew Yii Huei]

Replication steps:

1. Start up Ubuntu desktop as usual with HDMI cable connected to external monitor in extended desktop mode.
2. Log in to Ubuntu desktop.
3. Launch a few applications (e.g. browser, terminal, etc).
4. Disconnect HDMI cable.

Expected behaviour:

Desktop session should still be available on laptop screen after disconnecting HDMI cable.

Current behaviour:

Laptop screen goes black and shows the login screen. Logging in again shows a fresh desktop session (no open application windows).

Other information:

This is a dual-OS machine, with home directory encryption enabled for Ubuntu.
Installed from Mantic originally, and upgraded to Noble via command line.

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: ubuntu-desktop 1.539
ProcVersionSignature: Ubuntu 6.5.0-35.35-generic 6.5.13
Uname: Linux 6.5.0-35-generic x86_64
ApportVersion: 2.28.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Mon Jun 10 21:51:29 2024
EcryptfsInUse: Yes
InstallationDate: Installed on 2024-03-14 (88 days ago)
InstallationMedia: Ubuntu Legacy 23.10 "Mantic Minotaur" - Release amd64 (20231010)
SourcePackage: ubuntu-meta
UpgradeStatus: No upgrade log present (probably fresh install)

[AceLan Kao (acelankao)]

Looks like the X or Wayland crashes when HDMI cable is unplugged.

We may need below logs
1. dmesg with drm.debug=0x1e
2. sudo lspci -vvnn

[Anne Chew Yii Huei (annecyh)]

dmesg output with drm.debug=0x1e

[Anne Chew Yii Huei (annecyh)]

output for "sudo lspci -vvnn" after reproducing the issue and logging back in.

[AceLan Kao (acelankao)]

It's the gnome-shell crashes.

[86941.402557] gnome-shell[77896]: segfault at 140 ip 00007e53082487f6 sp 00007e52b37eafe0 error 4 in libc.so.6[7e5308228000+188000] likely on CPU 4 (core 8, socket 0)
[86941.402574] Code: 84 ed 74 60 e8 2b fd fd ff 49 8b 1c 24 49 89 c7 48 85 db 75 15 eb 36 0f 1f 44 00 00 49 8b 5c 24 08 49 83 c4 08 48 85 db 74 23 <44> 3a 2b 75 ed 4c 89 fa 48 89 de 4c 89 f7 e8 f7 fd fd ff 85 c0 75

Could you add "drm.debug=0x1e" to /etc/default/grub change the below line
   GRUB_CMDLINE_LINUX=""
to
   GRUB_CMDLINE_LINUX="log_buf_len=16M drm.debug=0x1e"
Then run
   sudo update-grub
and reboot to capture the dmesg log again after unplug the HDMI.

[Anne Chew Yii Huei (annecyh)]

Hi Acelan,

I've updated the grub file and saved the latest dmesg log.
Hope the log contains the info you expect.

Thanks!

[Daniel van Vugt (vanvugt)]

A segfault is unexpected, otherwise I would have just assumed this was bug 2050865...

To help us find the cause of the crash please follow these steps:

1. Run these commands:
    journalctl -b0 > journal.txt
    journalctl -b-1 > prevjournal.txt
and attach the resulting text files here.

2. Look in /var/crash for crash files and if found run:
    ubuntu-bug YOURFILE.crash
Then tell us the ID of the newly-created bug.

3. If step 2 failed then look at https://errors.ubuntu.com/user/ID where ID is the content of file /var/lib/whoopsie/whoopsie-id on the machine. Do you find any links to recent problems on that page? If so then please send the links to us.

Please take care to avoid attaching .crash files to bugs as we are unable to process them as file attachments. It would also be a security risk for yourself.

[Daniel van Vugt (vanvugt)]

Maybe this is still bug 2050865, and the segfault in the log isn't from disconnecting HDMI.

[Daniel van Vugt (vanvugt)]

If the HDMI port is connected to a secondary GPU then it might be bug 2069565.