Comment 0 for bug 1733662

In doing Ubuntu 17.10 regression testing, we've encountered one computer (boldore, a Cisco UCS C240 M4 [VIC]), that hangs about one in four times when running our cpu_offlining test. This test attempts to take all the CPU cores offline except one, then brings them back online again. This test ran successfully on boldore with previous releases, but with 17.10, the system sometimes (about one in four runs) hangs. Reverting to Ubuntu 16.04.3, I found no problems; but when I upgraded the 16.04.3 installation to linux-image-4.13.0-16-generic, the problem appeared again, so I'm confident this is a problem with the kernel. I'm attaching two files, dmesg-output-4.10.txt and dmesg-output-4.13.txt, which show the dmesg output that appears when running the cpu_offlining test with 4.10.0-38 and 4.13.0-16 kernels, respectively; the system hung on the 4.13 run. (I was running "dmesg -w" in a second SSH login; the files are cut-and-pasted from that.)

I initiated this bug report from an Ubuntu 16.04.3 installation running a 4.10 kernel; but as I said, this applies to the 4.13 kernel.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.10.0-38-generic 4.10.0-38.42~16.04.1
ProcVersionSignature: User Name 4.10.0-38.42~16.04.1-generic 4.10.17
Uname: Linux 4.10.0-38-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
Date: Tue Nov 21 17:36:06 2017
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: linux-hwe
UpgradeStatus: No upgrade log present (probably fresh install)