ubuntu 18.04 systemd-udevd进程CPU占用特别高，禁用WiFi可以解决，如下：
执行
udevadm monitor
，不断输出如下信息：
UDEV [13756.376116] bind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
KERNEL[13756.380620] bind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
KERNEL[13756.381300] unbind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
UDEV [13756.381674] unbind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
KERNEL[13756.392446] bind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
KERNEL[13756.393308] unbind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
UDEV [13756.393898] bind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
KERNEL[13756.397263] bind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
KERNEL[13756.398300] unbind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
UDEV [13756.398561] unbind /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0 (usb)
执行
dmesg
输出内容如下：
[13756.340234] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.346204] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.354209] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.362221] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.367210] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.375214] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.381236] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.393229] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.398213] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.407212] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.413235] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.425200] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.430295] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.438214] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.443217] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
[13756.454226] usb 8-2.2: usbfs: USBDEVFS_CONTROL failed cmd hid2hci rqt 33 rq 9 len 4 ret -71
执行
sudo /lib/systemd/systemd-udevd -D
,会发现持续输出如下信息：
RUN 'hid2hci --method=dell --devpath=%p' /lib/udev/rules.d/97-hid2hci.rules:11
starting 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'
seq 5913 queued, 'bind' 'usb'
'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'(err) 'error: switching device '/sys//devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0' failed.'
seq 5914 queued, 'unbind' 'usb'
Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0' failed with exit code 1.
seq 5893 processed
seq 5894 running
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
Process '/usr/sbin/obex-check-device 413c 8156' failed with exit code 1.
RUN 'VBoxCreateUSBNode.sh $major $minor $attr{bDeviceClass} vboxusers' /lib/udev/rules.d/60-virtualbox.rules:2
IMPORT builtin 'path_id' /lib/udev/rules.d/71-seat.rules:51
RUN 'uaccess' /lib/udev/rules.d/73-seat-late.rules:17
handling device node '/dev/bus/usb/008/017', devnum=c189:912, mode=0660, uid=0, gid=46
set permissions /dev/bus/usb/008/017, 020660, uid=0, gid=46
creating symlink '/dev/char/189:912' to '../bus/usb/008/017'
starting 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'
starting 'VBoxCreateUSBNode.sh 189 912 e0 vboxusers'
seq 5915 queued, 'bind' 'usb'
'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'(err) 'error: switching device '/sys//devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0' failed.'
seq 5916 queued, 'unbind' 'usb'
Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0' failed with exit code 1.
seq 5894 processed
'VBoxCreateUSBNode.sh 189 912 e0 vboxusers'(err) '/lib/udev/VBoxCreateUSBNode.sh: 35: test: Illegal number: e0'
seq 5895 running
RUN 'hid2hci --method=dell --devpath=%p' /lib/udev/rules.d/97-hid2hci.rules:11
starting 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'
seq 5917 queued, 'bind' 'usb'
'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'(err) 'Can't claim interface: Device or resource busy (16)'
'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0'(err) 'error: switching device '/sys//devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0' failed.'
Process 'hid2hci --method=dell --devpath=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2.2/8-2.2:1.0' failed with exit code 1.
这种情况，一般都算由于
Dell Wireless 370 Bluetooth
或者
Dell Wireless 1397 WLAN
驱动导致的，如下：
解决方法如下：
sudo rm -rf /lib/udev/rules.d/97-hid2hci.rules执行完成后，就可以不禁用无线网卡了。