I recently switched from Kubuntu 17.10 to Kubuntu 18.04 (fresh installed). The problem is the process systemd-udevd is constantly running and consuming 90-100% CPU load. After tinkering around with all devices I found out that it is because of WiFi! Once I turn on WiFi the process starts running and CPU load goes up to 100%. But whenever I turn off the WiFi it gets down to zero!
here is the top results when WiFi is on:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
338 root 20 0 94336 51744 3120 S 44.7 0.6 0:35.50 systemd-udevd
24957 root 20 0 67936 25248 2860 R 40.4 0.3 0:23.85 systemd-udevd
328 root 19 -1 150720 53068 52264 S 4.3 0.7 0:07.61 systemd-journal
and running: strace -p 338 makes the following output repeatedly:
strace: Process 338 attached
strace: [ Process PID=338 runs in x32 mode. ]
strace: [ Process PID=338 runs in 64 bit mode. ]
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}, {EPOLLIN, {u32=4010060672, u64=94544830180224}}], 11, 0) = 2
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=484799898}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=112300760}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=112454363}) = 0
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}, {EPOLLIN, {u32=4010060672, u64=94544830180224}}], 11, 0) = 2
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=485376240}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=112893238}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=113047679}) = 0
recvmsg(7, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="", iov_len=0}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, cmsg_data={pid=24957, uid=0, gid=0}}], msg_controllen=32, msg_flags=0}, MSG_DONTWAIT) = 0
recvmsg(7, {msg_namelen=0}, MSG_DONTWAIT) = -1 EAGAIN (Resource temporarily unavailable)
sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=-853365251, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base="libudev\0\376\355\312\376(\0\0\0(\0\0\0\315\0\0\0\5w\305\345\261\2Ge"..., iov_len=40}, {iov_base="ACTION=unbind\0DEVPATH=/devices/p"..., iov_len=205}], msg_iovlen=2, msg_controllen=0, msg_flags=0}, 0) = 245
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}], 11, 0) = 1
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=495431807}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=123814890}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=123945023}) = 0
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=0x000001}, msg_namelen=128->12, msg_iov=[{iov_base="unbind@/devices/pci0000:00/0000:"..., iov_len=8192}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, cmsg_data={pid=0, uid=0, gid=0}}], msg_controllen=32, msg_flags=0}, 0) = 243
getrandom("\x9c\x6d\x41\x2b\xb5\xf0\xf1\x9a\x32\xb3\x4a\x73\xee\x04\xff\x90", 16, GRND_NONBLOCK) = 16
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=126971116}) = 0
getrandom("\xaf\x35\x7a\x36\x01\x32\xa6\xe6\x13\x46\x4e\x22\xcc\x48\x77\x9b", 16, GRND_NONBLOCK) = 16
getrandom("\x48\x0b\xeb\xf1\xf0\x1c\xf1\x78\x89\xb7\x48\xe1\x84\x38\xc9\x3c", 16, GRND_NONBLOCK) = 16
getrandom("\x11\x06\x8c\x4a\xeb\xff\x84\x8e\x0c\x09\x00\x84\x62\x74\xfc\xd7", 16, GRND_NONBLOCK) = 16
getrandom("\xb5\x8e\x19\x16\xad\xf6\x16\x7e\x21\x66\x90\x12\x2d\x43\x46\x45", 16, GRND_NONBLOCK) = 16
getrandom("\x84\x7d\x47\x96\x50\x36\xad\x28\x06\x6e\xed\x33\xe0\x05\x57\x20", 16, GRND_NONBLOCK) = 16
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}, {EPOLLIN, {u32=4010060672, u64=94544830180224}}], 11, 0) = 2
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=504542288}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=131992368}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=132096027}) = 0
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}, {EPOLLIN, {u32=4010060672, u64=94544830180224}}], 11, 0) = 2
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=504955877}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=132438717}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=132555928}) = 0
recvmsg(7, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="", iov_len=0}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, cmsg_data={pid=24957, uid=0, gid=0}}], msg_controllen=32, msg_flags=0}, MSG_DONTWAIT) = 0
recvmsg(7, {msg_namelen=0}, MSG_DONTWAIT) = -1 EAGAIN (Resource temporarily unavailable)
sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=-853365251, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base="libudev\0\376\355\312\376(\0\0\0(\0\0\0\23\1\0\0\5w\305\345\261\2Ge"..., iov_len=40}, {iov_base="ACTION=bind\0DEVPATH=/devices/pci"..., iov_len=275}], msg_iovlen=2, msg_controllen=0, msg_flags=0}, 0) = 315
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}], 11, 0) = 1
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=512870505}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=140367037}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=140494166}) = 0
recvmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=0, nl_groups=0x000001}, msg_namelen=128->12, msg_iov=[{iov_base="bind@/devices/pci0000:00/0000:00"..., iov_len=8192}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, cmsg_data={pid=0, uid=0, gid=0}}], msg_controllen=32, msg_flags=0}, 0) = 311
getrandom("\x21\xcd\x52\xae\x20\xa4\xe9\x0f\x2c\x3f\x68\x8a\x77\x65\xfb\x22", 16, GRND_NONBLOCK) = 16
getrandom("\xb5\x1f\x43\xf7\x14\x3e\x29\x6c\xdd\x95\xd5\x64\xec\xec\x66\xca", 16, GRND_NONBLOCK) = 16
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=141295429}) = 0
getrandom("\xe7\x73\x2e\xc2\x5d\x71\x93\x8a\xd0\xf4\x5f\xd7\x91\x1f\x7b\x00", 16, GRND_NONBLOCK) = 16
getrandom("\xe4\xd4\xd3\x2c\xa2\xa1\x0c\x96\x6e\x6a\x34\x9c\x50\x06\x3d\x43", 16, GRND_NONBLOCK) = 16
getrandom("\xb0\x7f\xf7\x93\x1f\xa6\x6d\x2e\x01\xfb\x21\x97\x4b\xe8\x85\x14", 16, GRND_NONBLOCK) = 16
getrandom("\x3f\x94\x2b\x17\x01\x8f\x88\x2e\x08\xa0\x9d\xd0\xef\x4f\x0e\x9a", 16, GRND_NONBLOCK) = 16
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}, {EPOLLIN, {u32=4010060672, u64=94544830180224}}], 11, 0) = 2
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=519062044}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=146474265}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=146513033}) = 0
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}, {EPOLLIN, {u32=4010060672, u64=94544830180224}}], 11, 0) = 2
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=519231922}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=146636530}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=146675297}) = 0
recvmsg(7, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="", iov_len=0}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, cmsg_data={pid=24957, uid=0, gid=0}}], msg_controllen=32, msg_flags=0}, MSG_DONTWAIT) = 0
recvmsg(7, {msg_namelen=0}, MSG_DONTWAIT) = -1 EAGAIN (Resource temporarily unavailable)
sendmsg(3, {msg_name={sa_family=AF_NETLINK, nl_pid=-853365251, nl_groups=00000000}, msg_namelen=12, msg_iov=[{iov_base="libudev\0\376\355\312\376(\0\0\0(\0\0\0\315\0\0\0\5w\305\345\261\2Ge"..., iov_len=40}, {iov_base="ACTION=unbind\0DEVPATH=/devices/p"..., iov_len=205}], msg_iovlen=2, msg_controllen=0, msg_flags=0}, 0) = 245
epoll_wait(10, [{EPOLLIN, {u32=4010170080, u64=94544830289632}}], 11, 0) = 1
clock_gettime(CLOCK_REALTIME, {tv_sec=1524848329, tv_nsec=525080911}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1045, tv_nsec=152528058}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1045, tv_nsec=152611810}) = 0
....
running udevadm monitor prints the following repeatedly:
KERNEL[1464.842652] bind /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0 (usb)
KERNEL[1464.844393] unbind /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0 (usb)
UDEV [1464.845340] bind /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0 (usb)
KERNEL[1464.857728] bind /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0 (usb)
KERNEL[1464.858361] unbind /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0 (usb)
....
and running journalctl returns repeatedly:
Apr 27 05:22:09 amir-pc systemd-udevd[359]: Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3
Apr 27 05:22:09 amir-pc upowerd[1339]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0
-- Logs begin at Fri 2018-04-27 05:22:09 +0430, end at Fri 2018-04-27 21:37:15 +0430. --
Apr 27 05:22:09 amir-pc systemd-udevd[359]: Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3
Apr 27 05:22:09 amir-pc upowerd[1339]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0
Apr 27 05:22:09 amir-pc systemd-udevd[359]: Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3
Apr 27 05:22:09 amir-pc upowerd[1339]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0
....
running dmesg returns:
[ 441.582359] usb 3-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 441.582361] usb 3-1.3: Product: Dell Wireless 370 Bluetooth Mini-card
[ 441.582363] usb 3-1.3: Manufacturer: Dell Computer Corp
[ 450.803644] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.811642] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.819653] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.826650] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.833668] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.841644] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.848630] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.856628] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.863632] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.871611] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.881629] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.888616] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.896634] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.903596] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.910611] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.917595] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.926603] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.933598] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.942616] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.949606] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.957363] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.964607] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.973581] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.980582] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.987582] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 450.994561] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 451.004574] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 451.009525] ERROR @wl_cfg80211_scan :
[ 451.009527] WLC_SCAN error (-22)
[ 451.010550] usb 3-1.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[ 451.020078] usb 3-1: USB disconnect, device number 14
[ 451.020081] usb 3-1.1: USB disconnect, device number 15
[ 451.076974] usb 3-1.2: USB disconnect, device number 16
[ 451.077105] usb 3-1.3: USB disconnect, device number 19
[ 796.468102] usb 3-1: new full-speed USB device number 20 using uhci_hcd
[ 796.672318] usb 3-1: New USB device found, idVendor=0a5c, idProduct=4500
[ 796.672322] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 796.672325] usb 3-1: Product: BCM2046B1
[ 796.672328] usb 3-1: Manufacturer: Broadcom
[ 796.674239] hub 3-1:1.0: USB hub found
[ 796.676385] hub 3-1:1.0: 3 ports detected
[ 796.976059] usb 3-1.1: new full-speed USB device number 21 using uhci_hcd
[ 797.109323] usb 3-1.1: New USB device found, idVendor=413c, idProduct=8157
[ 797.109332] usb 3-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 797.116785] input: HID 413c:8157 as /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.1/3-1.1:1.0/0003:413C:8157.000B/input/input25
[ 797.176461] hid-generic 0003:413C:8157.000B: input,hidraw0: USB HID v1.11 Keyboard [HID 413c:8157] on usb-0000:00:1a.0-1.1/input0
[ 797.256314] usb 3-1.2: new full-speed USB device number 22 using uhci_hcd
[ 797.396307] usb 3-1.2: New USB device found, idVendor=413c, idProduct=8158
[ 797.396315] usb 3-1.2: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 797.405072] input: HID 413c:8158 as /devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0/0003:413C:8158.000C/input/input26
[ 797.464858] hid-generic 0003:413C:8158.000C: input,hidraw3: USB HID v1.11 Mouse [HID 413c:8158] on usb-0000:00:1a.0-1.2/input0
[ 797.564507] IPv6: ADDRCONF(NETDEV_UP): wlp4s0: link is not ready
[ 797.944045] usb 3-1.3: new full-speed USB device number 23 using uhci_hcd
[ 803.296508] usb 3-1.3: unable to read config index 0 descriptor/all
[ 803.296515] usb 3-1.3: can't read configurations, error -110
[ 803.376039] usb 3-1.3: new full-speed USB device number 24 using uhci_hcd
[ 808.672986] usb 3-1.3: unable to read config index 0 descriptor/all
[ 808.672993] usb 3-1.3: can't read configurations, error -110
[ 808.673984] usb 3-1-port3: attempt power cycle
[ 809.280029] usb 3-1.3: new full-speed USB device number 25 using uhci_hcd
[ 809.340944] usb 3-1.3: New USB device found, idVendor=413c, idProduct=8156
[ 809.340948] usb 3-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 809.340951] usb 3-1.3: Product: Dell Wireless 370 Bluetooth Mini-card
[ 809.340954] usb 3-1.3: Manufacturer: Dell Computer Corp
[ 1337.985097] perf: interrupt took too long (2508 > 2500), lowering kernel.perf_event_max_sample_rate to 79500
[ 1387.269440] perf: interrupt took too long (3140 > 3135), lowering kernel.perf_event_max_sample_rate to 63500
[ 1454.553305] perf: interrupt took too long (3927 > 3925), lowering kernel.perf_event_max_sample_rate to 50750
....
and running /lib/systemd/systemd-udevd -D returns below results repeatedly:
IMPORT builtin 'hwdb' /lib/udev/rules.d/50-udev-default.rules:14
RUN 'hid2hci --method=dell --devpath=%p' /lib/udev/rules.d/97-hid2hci.rules:11
starting 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0'
seq 284188 queued, 'bind' 'usb'
seq 284189 queued, 'unbind' 'usb'
'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0'(err) 'error: switching device '/sys//devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0' failed.'
Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0' failed with exit code 1.
seq 284184 processed
seq 284185 running
RUN 'hid2hci --method=dell --devpath=%p' /lib/udev/rules.d/97-hid2hci.rules:11
starting 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1.2/3-1.2:1.0'
seq 284190 queued, 'bind' 'usb'
seq 284191 queued, 'unbind' 'usb'
My fresh installed Kubuntu is using kernel version 4.15.0-20-generic and my laptop is a Dell Studio XPS 1640. WiFi is using bcmwl-kernel-source 6.30.223.271+bdcom-0ubuntu4 driver (downgrading to a previous working driver didn't solve the problem).
It's worth mentioning that no USB devices are connected, only a wireless mouse, which makes no problem (disconnecting it doesn't affect the problem). But as mentioned turning off WiFi always make the high CPU load disappear.
Best Answer
I installed Ubuntu 18.04 LTS (AMD64) on my Dell XPS Studio 1340 and I was suffering the same issue. I've solved it by completely disabling Bluetooth from the BIOS. I know it isn't a solution but a workaround, but it works for me because I rarely use Bluetooth.
It looks like a bug in the kernel or systemd without a fix yet: