Systemd uses CPU after wakeup due to power_supply BAT0 (battery) continued polling

[Jean]

My setup:
 - Dell Latitude 7520
 - Dell WD15 USB C docking station
 - Ubuntu 20.04.3
 - systemd 245.4-4ubuntu3.13
 - uname -a:
Linux CLIFMI085 5.13.0-1012-oem #16-Ubuntu SMP Tue Sep 7 09:23:08 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

I leave my laptop docked and, after waking it up from sleep, the fans start blowing. After a quick inspection with top/htop, I always see /usr/lib/systemd/systemd-udev consuming 50+% of my CPU.

After a quick search, I discover that I can use `udevadm monitor` to check what device is making all this fuss, and this is the output:

UDEV [92591.827159] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92591.873819] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92591.920022] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92591.967005] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.018200] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.068351] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.115100] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.166201] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.213318] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.261046] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.308824] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.356577] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.403766] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92592.451164] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)

As you can see, the battery status is being polled every 0.05s. To fix this, I just need to restart the service with:

sudo systemctl restart systemd-udevd systemd-udevd-kernel.socket systemd-udevd-control.socket

Afterwards, this is the output of `udevadm monitor`:

KERNEL[92739.612371] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92739.646888] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[92741.076823] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92741.099370] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[92742.539438] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV [92742.573812] change /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)

As you can see, the battery is now being polled every ~1.5s, which is fine.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Viktor Pal (deere)]

I experience the same issue on a Dell Latitude 3520.
It is Manjaro and systemd version is 249 but the issue/solution is exactly the same.
Did you find any permanent solution to the problem?

[Jean (alessandro-lai85)]

No, no workaround. I still have to do the restart at every reboot with the docking station attached.

My system is fully updated up to yesterday:

$ uname -a
Linux CLIFMI085 5.13.0-1021-oem #25-Ubuntu SMP Thu Dec 2 18:03:51 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

[Yao Wei (medicalwei)]

Could you try updating the BIOS firmware, and see whether this issue is still reproducible?

I cannot observe the issue with BIOS firmware version 1.13.0 with docking station DA310.

[Jean (alessandro-lai85)]

I don't have any BIOS update available; as I said, my laptop (Dell Latitude 7520) is fully updated.

$ sudo dmidecode -s bios-version
1.6.1

$ fwupdmgr get-updates | grep "Current version" -B2
Devices with no available firmware updates:
 • UEFI Device Firmware
 • UEFI Device Firmware
 • UEFI dbx
 • VMM3332 inside Dell WD15/TB16/TB18 wired Dock
│ │ Device ID: 71b677ca0f1bc2c5b804fa1d59e52064ce589293
│ │ Summary: NVM Express Solid State Drive
│ │ Current version: 21112012
--
└─System Firmware:
  │ Device ID: 5ecfc78eb81da0c1a2ab9baa1510f0c269ea1b9b
  │ Current version: 1.6.1

[Viktor Pal (deere)]

The difference between your and my setup is that I do not use a docking station.
Maybe worth a try if this also happens without it.

Upstream bug has been reported here: https://github.com/systemd/systemd/issues/21751
Also, I have a BIOS update that just came out so will install it right now and let you know if that helped.

[Kai-Chuan Hsieh (kchsieh)]

reply #5

Can you try $ fwupdmgr get-updates to see if you can see the latest firmware in LVFS? or attach your output here.

Also, you can always get latest BIOS here https://www.dell.com/support/home/en-in/product-support/product/latitude-15-7520-laptop/drivers, sometimes it is newer than BIOS in LVFS.

[Jean (alessandro-lai85)]

#7 output was already attached there, just grepped for brevity. The first lines where confusing me though, I've now upgraded the system BIOS from 1.6.1 to 1.12.2. 1.13 seems available on the official site, I'll report back ASAP on the results of the upgrade.

[Jean (alessandro-lai85)]

After first reboot with BIOS 1.12.2 all seems fine, the update seems even to have made the process of hooking up the docking station and activating the external monitors faster.

After first sleep and wakeup, no battery pinging that I can see with udevadm monitor, not even at a slow pace (but the battery is more than full).

Should I retry during battery recharge?

[Kai-Chuan Hsieh (kchsieh)]

The issue is first found on other platform during enablement, and the fix is landed in BIOS. Latitude 7520 has no problem with the BIOS version we certified, however, the regression should be caused by BIOS upgrade. Therefore, I assume the latest BIOS should contain fix for it. As I know, the issue should be observed whenever adapter is attached, if you can't see it, the issue should be fixed in the latest BIOS.

You can still monitor few days or do whatever experiment you'd like to do, until you think the issue is indeed fixed.

Again, thanks for reporting the issue.

[xiaoliang (liang-xiao1)]

For Latitude 7520, BIOS 1.7.1 should fix this issue.

[Jean (alessandro-lai85)]

Good. I woke up the laptop after leaving it hooked to the docking and in sleep the whole night, no issues.

I consider it resolved. Thanks.

[Viktor Pal (deere)]

Upgrading to BIOS 1.13.3 on Latitude 3520 seems to have solved the issue.
Thanks for the help.