Comment 0 for bug 1728760

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.