Using IPVS with One-Packet Scheduling on UDP causes CPU soft lockup on traffic.
Steps to reproduce:
1. Install ipvsadm and netcat-openbsd
2. Execute `ipvsadm -a -u 127.0.0.1:1234 -s rr --ops && ipvsadm -A -u 127.0.0.1:1234 -r 127.0.0.1:1235 -m -w 1`
3. Execute `nc -l -k -u 1235` to actually have a listening service
4. In another terminal, generate traffic `while sleep 0.01; do date | nc -u -w 0 127.0.0.1 1234; done`
In only takes several packets (around 100 in my tests) to cause the soft lockup to appear. Even with lower packet rates (sleep 1 for example), the bug occurs.
This problem is already fixed in the current 4.20 vanilla kernel but is present in the 4.15 vanilla kernel (tested packages from the kernel-ppa). So basically, this would be a backport.
Ubuntu release: Ubuntu 18.04.1 LTS
Kernel version: Ubuntu 4.15.0-43.46-generic 4.15.18
---
ProblemType: Bug
AlsaDevices:
total 0
crw-rw---- 1 root audio 116, 1 Jan 10 11:37 seq
crw-rw---- 1 root audio 116, 33 Jan 10 11:37 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
DistroRelease: Ubuntu 18.04
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lsusb:
Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: QEMU Standard PC (i440FX + PIIX, 1996)
Package: linux (not installed)
PciMultimedia:
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-43-generic root=UUID=27723a0b-84b7-4d41-ac73-d96bb9bc770a ro
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
RelatedPackageVersions:
linux-restricted-modules-4.15.0-43-generic N/A
linux-backports-modules-4.15.0-43-generic N/A
linux-firmware 1.173.2
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
Tags: bionic
Uname: Linux 4.15.0-43-generic x86_64
UnreportableReason: This report is about a package that is not installed.
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:
_MarkForUpload: False
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: rel-1.11.1-0-g0551a4be2c-prebuilt.qemu-project.org
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-2.12
dmi.modalias: dmi:bvnSeaBIOS:bvrrel-1.11.1-0-g0551a4be2c-prebuilt.qemu-project.org:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-2.12:cvnQEMU:ct1:cvrpc-i440fx-2.12:
dmi.product.name: Standard PC (i440FX + PIIX, 1996)
dmi.product.version: pc-i440fx-2.12
dmi.sys.vendor: QEMU
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 1811226
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.