[lxc-users] LXCFS and ProcPS Interaction Issue

[Robert Pendell]

On Mon, Jun 1, 2015 at 9:11 PM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> Quoting Robert Pendell (shinji at elite-systems.org):
>> On Mon, Jun 1, 2015 at 8:42 PM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
>> > Quoting Robert Pendell (shinji at elite-systems.org):
>> >> First some basic information so you know my environment...
>> >> Host: Linode
>> >> OS: Ubuntu 14.04.2
>> >> Kernel: Host supplied 4.0.1 -- also tested against PV-Grub loaded 4.1-RC4
>> >> Container Privilage: Unprivileged.
>> >> shinji at icarus:/proc> apt-cache policy lxcfs
>> >> lxcfs:
>> >>   Installed: 0.7-0ubuntu2~ubuntu14.04.1~ppa1
>> >>   Candidate: 0.7-0ubuntu2~ubuntu14.04.1~ppa1
>> >>   Version table:
>> >>  *** 0.7-0ubuntu2~ubuntu14.04.1~ppa1 0
>> >>         500 http://ppa.launchpad.net/ubuntu-lxc/daily/ubuntu/
>> >> trusty/main amd64 Packages
>> >>         100 /var/lib/dpkg/status
>> >>
>> >> I literally just noticed this today.  When LXCFS is started and
>> >> running ProcPS throws a Floating Point Exception.  I do not know why
>> >> this is the case.  Oddly enough stopping LXCFS on the host and
>> >> restarting the container makes the bug go away.  Ideas?  Anything I
>> >> can test to isolate?
>> >
>> > Can you build 0.9.0 from the wily sources, just to make sure this isn't
>> > somethign fixed upstream?
>> >
>> > Also, if you can run lxcfs under gdb and get stack trace when it crashes
>> > that woudl be helpful.
>> >
>> >> LXCFS Stopped
>> >> shinji at trusty-x86:~> ps u
>> >> USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
>> >> shinji    1506  0.0  0.1   5816  3536 pts/4    Ss+  12:42   0:00 -bash
>> >> shinji    1519  0.0  0.1   5404  2684 pts/4    S+   12:42   0:00 tmux -2 -f /usr
>> >> shinji    1573  0.3  0.1   5696  3412 pts/5    Ss   12:42   0:00 /bin/bash
>> >> shinji    1679  0.0  0.1   5228  2340 pts/5    R+   12:42   0:00 ps u
>> >>
>> >> LXCFS Started
>> >> shinji at trusty-x86:~> ps u
>> >> USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
>> >> Signal 8 (FPE) caught by ps (procps-ng version 3.3.9).
>> >> shinji    1521  0.0ps:display.c:66: please report this bug
>> >> Floating point exception
>> >>
>>
>> I could but I guess I forgot to mention on here that the issue was
>> already identified when I ran a ticket on LXC.
>
> Ah, great, thanks.
>

I went ahead and did that testing but I couldn't get lxcfs 0.9 to work
at all.  It built but it didn't seem to respond nor did LXC seem to
attempt to use it.  I removed lxcfs 0.7 before testing and had it
install in the default location (/usr/local).  At no time did it seem
like the container was using lxcfs as all /proc contents were a mirror
of the host.

However I did check /var/lib/lxcfs/proc and found that, once again,
meminfo was blank so it looks like that the issue does indeed persist
regardless.  The stacktrace was non-conclusive given that we already
know the scenario that needs handled/patched.

Robert Pendell
shinji at elite-systems.org
A perfect world is one of chaos.
Keybase: http://keybase.io/shinji257