I noticed that when I connect the AC_Adapter to my Thinkpad X1 carbon that the fan went full-throttle and CPU temp goes up to 76C and maybe more if I let it.
Using top I saw "systemd-udevd" maxing out 2 cores.
"udevadm monitor" tells me it's bluetooth/hci connected ....
It turns out using
"sudo systemctl stop systemd-udevd systemd-udevd-kernel.socket systemd-udevd-control.socket && sudo systemctl start systemd-udevd systemd-udevd-kernel.socket systemd-udevd-control.socket"
solves the problem ... until I connect again. Then it has to be run again or I simply dont run the start bit, but then I suspect I will not have bluetooth.
Hope this helps anyone having the same problem and ,maybe it'll be gone in newer kernel releases.
Intrerestingly just using the stop command and resuming from suspend (using dpms) ..... if the touchpad is lost, using a previous solution:
"sudo modprobe -r psmouse;sudo modprobe psmouse" doesn't work. It requires a start of the sockets first.