[lxc-users] LXCFS and ProcPS Interaction Issue

[Serge Hallyn]

Quoting Robert Pendell (shinji at elite-systems.org):
> 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

You probably should have used /usr.  Check where lxcfs 0.9 is putting it's
fs - presumably it's under /usr/local/var/lib/lxcfs instead of
/var/lib/lxcfs.  The lxcfs lxc hook may be trying to bind-mount from
/var/lib.

> 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,

(oh, yes, there it is)

> meminfo was blank so it looks like that the issue does indeed persist

Hm.

Can you show your /proc/meminfo?

> regardless.  The stacktrace was non-conclusive given that we already
> know the scenario that needs handled/patched.

Do we?  Sorry i don't seem to have that context handy.  Which scenario
is it?