An update: The problem I reported in January went away on its own after
a few weeks of having the problem every single day when I booted each
morning. I was installing Ubuntu software updates when they became
available during that time. There is something going on during boot that
causes this problem.

"my speculation" is that I suspect a timing issue with the way things
are initialized during boot up that leads to the problem. Some strange
timing issue is occurring which causes systemd-udevd to fall into an
infinite loop (continuously looking for something or to be notified
about an action completion) and drive one of the processor cores to
100%. When a new kernel was installed or something was done to change
initialization activity during boot the problem went away because the
timing problem that created it was changed. I believe that some kind of
race condition may be at the root of the problem.

>From my earlier search on the problem symptoms, it seems that when
systemd-udevd isn't working correctly you can get numerous confusing
symptoms that mysteriously go away when the something changes timing
conditions during boot. Since the problem is in the kernel then it
effects other systems besides Ubuntu.

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  udevd keeps binding and unbinding some usb device und uses all cpu

Status in Linux:
Status in linux package in Ubuntu:

Bug description:
  It first appeared when I upgraded ubuntu studio to 18.04
  udevd started to use all available cpu.
  now I'm running ubuntu desktop from a usb key and it's still the same

  udevadm monitor returns:
  KERNEL[2512.539491] unbind   
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  UDEV  [2512.540201] bind     
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  KERNEL[2512.566574] bind     
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  KERNEL[2512.566866] unbind   
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  UDEV  [2512.567499] unbind   
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  KERNEL[2512.594050] bind     
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  KERNEL[2512.594310] unbind   
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  UDEV  [2512.596510] bind     
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  KERNEL[2512.620736] bind     
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  KERNEL[2512.624606] unbind   
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)
  UDEV  [2512.634706] unbind   
/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1/1-1.1.2/1-1.1.2:1.0 (usb)

  WORKAROUND: Remove file:

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: udev 237-3ubuntu10.3
  ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
  Uname: Linux 4.15.0-29-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.2
  Architecture: amd64
  CasperVersion: 1.394
  CustomUdevRuleFiles: 70-snap.core.rules
  Date: Mon Aug 20 18:54:48 2018
  ExecutablePath: /lib/systemd/systemd-udevd
  LiveMediaBuild: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
  MachineType: Dell Inc. Vostro 3300
   PATH=(custom, no user)
  ProcKernelCmdLine: file=/cdrom/preseed/hostname.seed boot=casper 
initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
  SourcePackage: systemd
  UpgradeStatus: No upgrade log present (probably fresh install) 02/10/2010
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A01 07JC8T
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.chassis.version: Not Specified
dmi:bvnDellInc.:bvrA01:bd02/10/2010:svnDellInc.:pnVostro3300:pvrNotSpecified:rvnDellInc.:rn07JC8T:rvrA00:cvnDellInc.:ct8:cvrNotSpecified: Vostro 3300
  dmi.product.version: Not Specified
  dmi.sys.vendor: Dell Inc.

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