[Lxc-users] [PATCH 2/2] cgroups: support cgroups mounted in multiple places

[Michael H. Warfield]

On Sun, 2011-06-26 at 18:27 +0200, Daniel Lezcano wrote: 
> On 06/26/2011 05:52 PM, Michael H. Warfield wrote:
> > On Sun, 2011-06-26 at 17:27 +0200, Daniel Lezcano wrote: 
> >> On 06/26/2011 05:06 PM, Serge E. Hallyn wrote:
> >>> Quoting Michael H. Warfield (mhw at WittsEnd.com):
> >>>>> cd /sys/fs/cgroup
> >>>>>    for d in `/bin/ls`; do
> >>>>>       echo 1 > $d/cgroup.clone_children
> >>>>>    done
> >>>>
> >>>> Doing this step alone broke lxc totally for me, with or without the
> >>>> patch below.  This was on Fedora 15 testing with lxc 0.7.4.2 as well as
> >>>
> >>> Do you have the ns cgroup mounted?  The above is only for without
> >>> ns cgroup.
> > 
> >> Yes, the ns_cgroup and clone_children are mutually exclusive.
> > 
> >> If you try to create a namespace with a ns cgroup mounted and the
> >> clone_children flag is set. The 'clone' will return EINVAL.
> > 
> >> I noticed with the patch applied because there was a bug in it which was
> >> setting this flag even if the cgroup was ns.
> > 
> >> It is possible, you ran lxc with the patch, the clone_children was set,
> >> and then you remove the patch and try to run lxc again. As the
> >> clone_children is still set, that will make impossible to clone a new
> >> namespace.
> > 
> >> With the patch I sent previously on top of Serge's patch, that should be
> >> fixed.
> > 
> > Ok...  Got that an threw it into the mix.
> > 
> > I'm still seeing the segfaults on lxc-info.  Seems to fault even if I
> > specify the name of a non-existent machine as well.

> Oh, seems I missed this info :s

> If you launch lxc-info -n foo, that segfaults ?

> On what architecture does it fault ?

Fedora 15, x86_64.

0.7.4.2 is fine.

Just rebuilt a fresh set of packages from GIT sources alone.  They're
fine and lxc-info from git works.

Git patched with Serge's patch.  Segfault.

Git patched with both patches.  Segfault.

Here's what gdb has to say about it:

[root at forest lxc]# gdb lxc-info core.13546 
GNU gdb (GDB) Fedora (7.2.90.20110525-39.fc15)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/mhw/rpmbuild/BUILD/lxc-0.7.4.2git2/src/lxc/lxc-info...done.
[New LWP 13546]
Core was generated by `./lxc-info -n Alcove'.
Program terminated with signal 11, Segmentation fault.
#0  lxc_cgroup_path_get (path=0x7fff89b35928, subsystem=0x7fba52a4fdc1 "freezer", name=0x7fff89b3987d "Alcove") at cgroup.c:326
326	               *s = '\0';
(gdb) trace
Tracepoint 1 at 0x7fba52a41e74: file cgroup.c, line 326.
(gdb) backtrace
#0  lxc_cgroup_path_get (path=0x7fff89b35928, subsystem=0x7fba52a4fdc1 "freezer", name=0x7fff89b3987d "Alcove") at cgroup.c:326
#1  0x00007fba52a4a337 in freezer_state (name=<optimized out>) at state.c:74
#2  0x00007fba52a4a42d in lxc_getstate (name=0x7fff89b3987d "Alcove") at state.c:130
#3  0x000000000040068d in main (argc=<optimized out>, argv=<optimized out>) at lxc_info.c:63

Regards,
Mike
-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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