group.of.nepali.translators team mailing list archive

[Tim Gardner <1944642@xxxxxxxxxxxxxxxxxx>]

Hi Kenneth - Since you already have the environment and reproducer, it
would likely be faster if I build bisect kernels to narrow down the
offending commit. It will probably take 6-8 attempts. Do you have the
time for that ?


** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Xenial)
     Assignee: (unassigned) => Tim Gardner (timg-tpi)

** Changed in: linux (Ubuntu Xenial)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1944642

Title:
  Xenial (ESM) - 4.15.0-156 creates event storm when ejecting DVD-ROM
  media

Status in linux package in Ubuntu:
  Incomplete
Status in linux source package in Xenial:
  In Progress

Bug description:
  Hello! I'm a programmer employed by VMWare. We're using Ubuntu Xenial,
  have an ESM contract, and have run into what we believe to be a nasty
  interaction between a kernel change and the `cdrom_id --eject-media`
  command. This problem started happening after upgrading from
  4.15.0-154 to 4.15.0-156.

  I am reporting a kernel "device change" event storm that appears to
  not stop on its own and is triggered by both ejecting media from a
  DVD-ROM drive AND having a udev rule which contains the following
  line:

  ENV{DISK_EJECT_REQUEST}=="?*", RUN+="cdrom_id --eject-media $devnode",
  GOTO="cdrom_end"

  If you eliminate this line from your udev rule file, the storm will
  never happen. This strongly suggests that the cdrom_id program is a
  key component in the problem. As mentioned before, this problem
  happened after we upgraded from kernel 4.15.0-154 to kernel 4.15.0-156
  as part of a regular update to the Canonical-included packages that we
  use as a base for our system. Based on the evidence, we believe that
  this is a regression from kernel version 4.15.0-154.

  This storm prevents new media inserted into the drive from being
  recognized and mounted. In order for any new media inserted into the
  drive to be recognized, one must terminate the storm by do one of two
  things:

  Either:
  Move `/lib/udev/cdrom_id` to some other location, wait for a moment for the storm to stop, then move it back. Media inserted into the drive will be immediately recognized.
  or:
  Insert the media several times until it stays inserted. In testing "several" has been "three or four", but I have no idea of the upper or lower bounds of this number. Each time you insert the media, it will be automatically removed from the VM. On the insertion immediately _before_ the one that actually works, the event storm will stop, and the media will be -again- automatically removed. On the next insertion, the media will stay in, and you will be able to actually mount the media inside the VM.

  When you look at the output of `udevadm monitor -u -k` during the
  event storm the following event is generated at a rate roughly ten
  times per second:

  KERNEL[3198.914510] change   /devices/pci0000:00/0000:00:07.1/ata1/host0/target0:0:0/0:0:0:0/block/sr0 (block)
  UDEV  [3199.021261] change   /devices/pci0000:00/0000:00:07.1/ata1/host0/target0:0:0/0:0:0:0/block/sr0 (block)

  
  Relevant system information:
  OS:  Ubuntu Xenial ESM
  IAAS: vSphere 7.0
  uname -a output: Linux test-machine 4.15.0-156-generic #163~16.04.1-Ubuntu SMP Mon Aug 23 13:38:23 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

  Likely Reproduction Steps:
  1) Boot a machine (virtual or otherwise) with an attached DVD-ROM drive with the 4.15.0-156-generic kernel.
  2) Insert media into the drive.
  3) Eject the media.
  4) Notice that `udevadm monitor -u -k` is showing you an endless stream of "device change" events.

  If you need any additional information or resources from us, please
  don't hesitate to ask. I expect that if you folks need a vSphere
  environment, we'll be able to provide one.

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