[Bug 1728760] Re: 17.04 to 17.10 dist upgrade automatically switched me to lowlatency kernel

[James]

** Attachment added: "history.log"
   https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1728760/+attachment/5005106/+files/history.log

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https://bugs.launchpad.net/bugs/1728760

Title:
  17.04 to 17.10 dist upgrade automatically switched me to lowlatency
  kernel

Status in ubuntu-release-upgrader package in Ubuntu:
  Incomplete

Bug description:
  When I upgraded from 17.04 to 17.10, I was automatically switched from
  the generic kernel to the lowlatency kernel. I did not have the
  lowlatency kernel installed prior to the dist upgrade (I have verified
  this by inspecting my /var/log/apt/history.log* files, all upgrades
  prior to the dist upgrade only show updating *-generic kernel
  packages, if I had lowlatency installed it would show that as well.)
  I'm not sure why I was switched to lowlatency, I don't see anything in
  the release notes saying that there was a switch to lowlatency as the
  default, and other users who have just done a dist upgrade weren't
  switched to lowlatency. So I think it is probably a bug that I was
  switched to lowlatency - perhaps there's a package that I have
  installed that is incorrectly depending on the lowlatency kernel in
  17.10? I'm not sure how to find out if that's the case.

  To be explicit, after the dist-upgrade, I had both the
  4.13.0-16-generic and 4.13.0-16-lowlatency kernels installed, and by
  default 4.13.0-16-lowlatency was what was booted into.

  This also caused a problem when I did the upgrade - perhaps this is a
  separate bug that I should report, let me know and I'll do that. After
  the dist-upgrade, wifi didn't work. I have a BCM4352 wifi card, whose
  driver is provided by the bcmwl-kernel-source package, which uses DKMS
  to compile it. Presumably during the dist-upgrade, the driver was
  compiled for the 4.13.0-16-generic kernel, so when I manually selected
  that kernel on boot, it worked, but it wasn't compiled for the
  4.13.0-16-lowlatency kernel, which is why wifi didn't work out of the
  box after the dist-upgrade. The solution was of course straight
  forward, I had to reinstall the bcmwl-kernel-source package, but a non
  working system after an upgrade requiring reinstalling packages or
  booting into a different kernel to fix is presumably a bug.

  If the switch from generic to lowlatency was a feature, not a bug,
  then such a switch should also be accompanied by compiling all the
  kernel modules that were compiled against the generic kernel against
  the new lowlatency kernel, so as to ensure the system is in a working
  state after completing a dist upgrade. Also, if the switch is a
  feature, then I would expect it to be documented in the release notes
  with a brief explanation or link to more information on why the switch
  was done.

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