Major networking regression linux-image-5.4.0-42-generic

[Carl-Johan Kjellander]

When booting into linux-image-5.4.0-42-generic networking grinds to a halt. It is 10000x times slower than usual.

Selecting an older kernel like linux-image-5.3.0-62-generic makes networking normal again.

Description: Ubuntu 18.04.4 LTS
Release: 18.04

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-5.4.0-42-generic 5.4.0-42.46~18.04.1
ProcVersionSignature: Ubuntu 5.3.0-62.56~18.04.1-generic 5.3.18
Uname: Linux 5.3.0-62-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
Date: Wed Aug 19 11:11:51 2020
InstallationDate: Installed on 2019-11-19 (273 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
SourcePackage: linux-signed-hwe-5.4
UpgradeStatus: No upgrade log present (probably fresh install)

[Stefan Bader (smb)]

Could you please run (while running the 5.4 kernel)

sudo apport-collect -p linux 1892163

That should add more information about hardware and content of logfiles. Also you could try to enable the PPA where upcoming kernel releases are made available for testing:

sudo apt-add-repository ppa:canonical-kernel-team/proposed

To get rid of the additional PPA later, you can run

sudo apt-add-repository --remove ppa:canonical-kernel-team/proposed

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

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1892163

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Carl-Johan Kjellander (x-carljohan)]

I'm having lots of troubles with apport-collect since the network is so bad in 5.4.0, I tried apport-bug --save linux.apport linux, but that just locks up for 10 minutes.

Is there any way I can run this offline and then send it with 5.3.0?

Or what info do you need that I can run by hand and post? dmesg? lspci? boot logs? all installed packages?

[Carl-Johan Kjellander (x-carljohan)]

Also, running sudo apport-collect will not work since it can't attach to my firefox not running as root. But I did manage to get an authorization twice into my cache.

[Stefan Bader (smb)]

Does "apport-cli --save tmpreport -f -p linux" work for you? The documentation claims one could then later use that file.

[Carl-Johan Kjellander (x-carljohan)]

It works super nice, in 5.3.0....

in 5.4.0 it just keeps going and going for over 10 minutes before I give up.

It literally takes seconds in 5.3.0, I can send that one.

[Carl-Johan Kjellander (x-carljohan)]

More info, I am using wifi for the network. 5G

[Hui Wang (hui.wang)]

You could compare the dmesg of 5.3 kernel and 5.4 kernel, for those lines which contains the iwlwifi.

In your 5.4 kernel dmesg:
[ 2.757791] compat: loading out-of-tree module taints kernel.
[ 2.757807] compat: module verification failed: signature and/or required key missing - tainting kernel
[ 2.757934] Loading modules backported from iwlwifi
[ 2.757934] iwlwifi-stack-public:master:8324:9176b151

Looks like your 5.4 kernel load an out-of-tree wifi driver. And please also compare the "loading firmware part" of iwlwifi.

[Hui Wang (hui.wang)]

And I just have a lenovo laptop which has the same wifi card as yours (8086:2723), I boot the 5.4.0-42 kernel and use the in-tree iwlwifi driver + iwlwifi-cc-a0-48.ucode firmware, the network works normally.

So I suggest you temporarily uninstall the iwlwifi dkms and do a test.

[You-Sheng Yang (vicamo)]

Hi, on 5.0 or newer kernel, you should not be using backport-iwlwifi-dkms as all the drivers are already in position. And since latest version of backport-iwlwifi-dkms in Bionic should be 7906, you should remove that manually install copy.

[Stefan Bader (smb)]

Thanks, You-Sheng and Hui, I would suggest (and maybe that is what you meant) to use dkms (remove or uninstall for the 5.4 kernel version) to drop the built dkms module from the 5.4 kernel as a first test. That way it is available for any older kernel as long as they are kept.
If this works and it is unlikely to have to go back to 5.3, then it is better to completely remove the backport driver. Otherwise it gets rebuild/installed for every kernel update.

I would also take back (at least for now) the wont-fix status for the dkms package. With the 5.4 kernel being the latest HWE kernel for Bionic, we should see whether we can make it not compiling for 5.4.

[You-Sheng Yang (vicamo)]

For the one available in Bionic, version 7906-0ubuntu4~18.04.2 latest updated for bug 1886911, it compiles, but no ko will be installed.

[Stefan Bader (smb)]

Oh I see, so this would not have happened with the official dkms package. Thanks. In that case yes, wont-fix.

[Vin (vinuji)]

Folks, I've got Ubuntu mate 18.04 LTS and recently installed the updates which brought it upto Kernel 5.4.xxx
This has definitely caused issues with my network speed. It has become extremely slow. Wifi using Fibre broadband 35Mbps.. Feels like browsing on a modem.. Is there a fix coming soon..