WiFi works on kernel version LL 115 but not LL 117

[Michael F Winthrop]

Running on Linux Kubuntu "latest" version, silent install notified me that re-boot is needed to install latest updates. I re-booted, and suddenly had no WiFi. I then used an Ethernet connection to ensure that Internet was still functional. I rebooted to kernel low latency 115 and WiFi returned (disconnected Ethernet before reboot).
I then rebooted again to kernel low latency version 117, with Ethernet, and ran "$ ubuntu-bug linux" which gave me:

QXcbConnection: XCB error: 3 (BadWindow), sequence: 1098, resource id: 25174330, major code: 40 (TranslateCoords), minor code: 0

and opened this bug report in LL 117 using Ethernet connection. I would have included LL 115 report for comparison, but there is no bug "save" option I know of.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-117-lowlatency 4.15.0-117.118
ProcVersionSignature: Ubuntu 4.15.0-117.118-lowlatency 4.15.18
Uname: Linux 4.15.0-117-lowlatency x86_64
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC2: dad 4716 F.... pulseaudio
 /dev/snd/controlC0: dad 4716 F.... pulseaudio
CurrentDesktop: KDE
Date: Tue Sep 8 11:30:04 2020
HibernationDevice: RESUME=UUID=540c3467-7148-463e-858a-cb1435e4503f
IwConfig:
 lo no wireless extensions.

 enp9s0 no wireless extensions.
MachineType: Dell Inc. Inspiron 1545
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-117-lowlatency root=UUID=27aec088-dbbf-44f9-9c61-ab3c933e054e ro quiet splash vt.handoff=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-117-lowlatency N/A
 linux-backports-modules-4.15.0-117-lowlatency N/A
 linux-firmware 1.173.19
RfKill:

SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/17/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A10
dmi.board.name: 0G848F
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA10:bd07/17/2009:svnDellInc.:pnInspiron1545:pvr:rvnDellInc.:rn0G848F:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Inspiron 1545
dmi.sys.vendor: Dell Inc.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Michael F Winthrop (mwinthrop-1)]

Problem Solved: I fixed the issue with:

sudo apt-get install --reinstall linux-image-4.15.0-117-lowlatency
sudo apt-get install --reinstall linux-headers-4.15.0-117-lowlatency
sudo apt-get install --reinstall linux-image-4.15.0-117-generic

What I saw was that VirtualBox was also corrupt in the 117 O/S but not in the 115 version. The solution above fixed the WiFi and VirtualBox.

Please note that I generally do not like using Discover to run updates. I prefer:
sudo apt update
sudo apt upgrade

Sometimes Discover locks updates from the command prompt, and I have to kill the locks. Discover takes a long time to do updates. I thought the "silent upgrade" was a new feature of Discover.

The "bot" upgrade was something new to me, and now I think that it might be a security problem.

[Michael F Winthrop (mwinthrop-1)]

Same problem again with update (manual this time) kubuntu 18.04 update to "Ubuntu 4.15.0-123.126-lowlatency 4.15.18" deletes WiFi but Ubuntu 4.15.0-122.124-lowlatency 4.15.18 works wifi correctly.

[Michael F Winthrop (mwinthrop-1)]

Same fix worked again. Must be a problem in the upgrade script. I noticed that the header files were pulled in with the broken wifi original upgrade (which usually does not happen and I have to do that after the upgrade). When I just did the reinstall of the upgrade the install of the kernel complained I had no header files. I therefore reinstalled them also. Now all WiFi works. Have not checked anything else yet.

Cheers

[Michael F Winthrop (mwinthrop-1)]

Since that time, I determined that the cause of this problem is that I have two kernels for each kernel release: lowlatency and generic. The upgrade puts the headers in for generic whether I am running lowlatency when the silent upgrade takes place or do the upgrade in a terminal window by hand. Therefore, the upgrade does not check to see if I have the same release in both lowlatency and generic. I have to remember to install the headers for lowlatency after any kernel update. Since the header update includes virtualbox updates I analyze that this solves the failed WiFi and Virtualbox corruption I found before I realized the headers were not up to date. The failed WiFi and Virtualbox were disguised because I could boot partially with previous low latency headers but not correctly. The ethernet hid the WiFi problem.

I recommend that upgrades for kernels and headers be scripted for when both lowlatency and generic (when present).