[Bug 1928997] [NEW] powerdevil occasionally stops responding until manually suspended

[Nathaniel Beaver]

Public bug reported:

About twice a month or so, my laptop exhibits the following symptoms:

1. Adjusting the brightness with the usual keys no longer works.

2. Closing the lid no longer suspends

3. Plugging in or unplugging no longer updates the battery charging
icon.

When this happens, I run this command:

systemctl suspend

and after opening the lid and unlocking, everything works again.

Based on these symptoms and workaround, I believe this is a bug in
powerdevil. I first recorded it occurring in version 5.12.7-0ubuntu0.1
in 2019, but it persists in version 5.12.8.

Note that this is not a duplicate of bug #1766683:

https://bugs.launchpad.net/ubuntu/+source/powerdevil/+bug/1766683

Most of the time, closing the lid does suspend my laptop, and I have
lidAction=1 already set (see attached powermanagementprofilesrc).

I would greatly appreciate suggestions for debugging. Currently I have
tried looking at the output of:

systemctl status upower.service

systemctl status org.kde.powerdevil.backlighthelper.service

acpi -V

systemd-inhibit --list

journalctl --boot --lines=all | grep powerdevil

grep powerdevil ~/.xsession-errors

as well as running strace and gdb on the powerdevil process when it is
unresponsive, but I haven't turned up anything useful. (I've attached it
anyway in case anyone can make use of it.)

$ lsb_release -rd
Description:	Ubuntu 18.04.5 LTS
Release:	18.04

$ apt-cache policy powerdevil
powerdevil:
  Installed: 4:5.12.8-0ubuntu0.1
  Candidate: 4:5.12.8-0ubuntu0.1
  Version table:
 *** 4:5.12.8-0ubuntu0.1 500
        500 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages
        100 /var/lib/dpkg/status
     4:5.12.4-0ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: powerdevil 4:5.12.8-0ubuntu0.1
ProcVersionSignature: Ubuntu 5.4.0-72.80~18.04.1-generic 5.4.101
Uname: Linux 5.4.0-72-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.23
Architecture: amd64
CurrentDesktop: KDE
Date: Wed May 19 20:21:10 2021
InstallationDate: Installed on 2020-02-01 (473 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
SourcePackage: powerdevil
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: powerdevil (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic

** Attachment added: "powermanagementprofilesrc"
   https://bugs.launchpad.net/bugs/1928997/+attachment/5498831/+files/powermanagementprofilesrc

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Title:
  powerdevil occasionally stops responding until manually suspended

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