Comment 70 for bug 1759836

Had the same problem on Dell Latitude E6400 laptop using Gentoo Linux with udev versions newer than udev-233. Disabling Bluetooth in BIOS solved the issue, however, I need bluetooth. Researching the web resulted in this page:

https://askubuntu.com/questions/1028883/ubuntu-18-04-systemd-udevd-uses-high-cpu-conflict-with-wifi

Following the instructions mentioned by one user in the comments helped me to solve the cpu load issue with udev-239 and kernel 4.18.17, while Bluetooth still works.

Run the following command:

/lib/systemd/systemd-udevd -D

This should print garbage in endless loop containing ".../97-hid2hci.rules:"

If so, edit /lib/udev/rules.d/97-hid2hci.rules

and add

ACTION=="add",

in front of line mentioned by above command.

In my case, I had to change the following lines in 97-hid2hci.rules from:

ATTR{bInterfaceClass}=="03", ATTR{bInterfaceSubClass}=="01", ATTR{bInterfaceProtocol}=="02", \
  ATTRS{bDeviceClass}=="00", ATTRS{idVendor}=="413c", ATTRS{bmAttributes}=="e0", \
  RUN+="hid2hci --method=dell --devpath=%p", ENV{HID2HCI_SWITCH}="1"

to:

ACTION=="add", ATTR{bInterfaceClass}=="03", ATTR{bInterfaceSubClass}=="01", ATTR{bInterfaceProtocol}=="02", \
  ATTRS{bDeviceClass}=="00", ATTRS{idVendor}=="413c", ATTRS{bmAttributes}=="e0", \
  RUN+="hid2hci --method=dell --devpath=%p", ENV{HID2HCI_SWITCH}="1"

And this fixed the issue (after reboot).

Best regards
Florian