Emergency shell ddcutil

Support
1

For about the last month I’m getting a 1 out of 4 chance that I boot into the emergency shell. The problem seams to be ddcutil, anyone else has ran into this problem? Maybe have advice how to fix/debug this?

# journalctl --boot=0 --priority=2 --catalog --no-pager
Sep 26 07:55:25 benihime systemd-coredump[893]: [🡕] Process 685 (ddcutil) of user 0 dumped core.
                                                
                                                Stack trace of thread 685:
                                                #0  0x00007f7d6dd4e61c n/a (libc.so.6 + 0x17f61c)
                                                #1  0x0000555c3bc01031 strsplit (ddcutil + 0x8b031)
                                                #2  0x0000555c3bc134ba n/a (ddcutil + 0x9d4ba)
                                                #3  0x0000555c3bc13778 is_possible_monitor_by_hiddev_name (ddcutil + 0x9d778)
                                                #4  0x0000555c3bc138a9 check_usb_monitor (ddcutil + 0x9d8a9)
                                                #5  0x0000555c3bb91752 main (ddcutil + 0x1b752)
                                                #6  0x00007f7d6dbf4e08 n/a (libc.so.6 + 0x25e08)
                                                #7  0x00007f7d6dbf4ecc __libc_start_main (libc.so.6 + 0x25ecc)
                                                #8  0x0000555c3bb91895 _start (ddcutil + 0x1b895)
                                                ELF object binary architecture: AMD x86-64
░░ Subject: Process 685 (ddcutil) dumped core
░░ Defined-By: systemd
░░ Support: https://forum.manjaro.org/c/support
░░ Documentation: man:core(5)
░░ 
░░ Process 685 (ddcutil) crashed and dumped core.
░░ 
░░ This usually indicates a programming error in the crashing program and
░░ should be reported to its vendor as a bug.

After exiting the emergency shell the system boots normally and I dont see any problem.

Also reported upstream

2

My thoughts:

Your title says “kernel panic”

What you posted is evidence of a core dump because of ddcutil failing.
Not a kernel panic - or is the panic happening right after?

On a kernel panic, the system usually just stops - you don’t get to go anywhere after a panic occurs.
But you said you get to an emergency shell on boot.

There might be no evidence in the logs when the panic happens before the initrd can switch over to the real root.
In that case: disable quiet and splash in /etc/default/grub
so that you can see the text messages scroll by and maybe can see a hint as to why the panic occurs.

3

you are right, that was a big brain fart :smiley: there is no kernel panic just booting into emergency shell.

4

… still:
either hit ESC real quick or

update-grub afterwards …

so that you don’t get the splash screen and can see the messages - they may be cryptic, but they usually tell you why you are thrown to an emergency shell

5

I found this report that seams to be the same, looks like ddcutil needs to be updated by the maintainers.

If ddcutil is built with configure option –enable-usb=no, ddcutil is built without support for USB communication. In this case command ddcutil chkusbmon is not built, and the udev rule is not installed.

As an alternative to building from branch 2.1.5-dev, you can simply delete file /usr/lib/udev/rules.d/60-ddcutil-usb.rules.

6

The USB rules were removed and the changes are available with 2.1.4-2 currently only in the Manjaro unstable branch.

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7

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