[lxc-users] LXCFS and ProcPS Interaction Issue

[Robert Pendell]

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.

The issue is identified by LXCFS not handling the situation where
/proc/meminfo is empty.  I don't see a change that would make it
handle it better in 0.9.  The empty scenario happens in a few
conditions.

The memory cgroup isn't compiled into the kernel being used at all
The memory cgroup functions are compiled in but are disabled at boot
time (cgroup_disable=memory)
The memory cgroup functions are compiled in but are disabled by
default at boot time

See ticket: https://github.com/lxc/lxcfs/issues/30

The first scenario applies to me above.

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