Re: cgroup tasks file error

[ccmail111 <ccmail111-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>]

Hi Serge,

Thanks for the tip. 
It seems to work (no ns).

[host:~]$ mount -t cgroup cpuset -ocpuset /dev/cgroup
[host:~]$ ls /dev/cgroup
cgroup.procs                    cpuset.memory_spread_page
cpuset.cpu_exclusive            cpuset.memory_spread_slab
cpuset.cpus                     cpuset.mems
cpuset.mem_exclusive            cpuset.sched_load_balance
cpuset.mem_hardwall             cpuset.sched_relax_domain_level
cpuset.memory_migrate           notify_on_release
cpuset.memory_pressure          release_agent
cpuset.memory_pressure_enabled  tasks

$ps aux | grep daemon
root       572  0.0  0.9  88816  2216 ?        Sl   18:25   0:00 myproc --daemon

[host:~]$ mkdir /dev/cgroup/hello
[host:~]$ echo 0 > /dev/cgroup/hello/cpuset.mems
[host:~]$ echo 0 > /dev/cgroup/hello/cpuset.cpus
[host:~]$ echo 572 > /dev/cgroup/hello/tasks
[host:~]$ cat /dev/cgroup/hello/tasks
572

Now move it back..

[host:~]$ echo 572 > /dev/cgroup/tasks

check:
[host:~]$ cat /dev/cgroup/hello/tasks
[host:~]$
[host:~]$ cat /dev/cgroup/tasks | grep 572
572
[host:~]$ id
uid=0(root) gid=0(root) groups=0(root)
[host:~]$

Thanks everyone !




--- On Tue, 12/14/10, Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> wrote:

> From: Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
> Subject: Re: cgroup tasks file error
> To: "ccmail111" <ccmail111-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>
> Cc: "Jue Hong" <honshj-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, "Matt Helsley" <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> Date: Tuesday, December 14, 2010, 12:40 PM
> Quoting ccmail111 (ccmail111-/E1597aS9LQAvxtiuMwx3w@public.gmane.org):
> > 
> > Isn't ns mounted by default ?
> 
> I thought that in an earlier email you said you had done
> 
>     mount -t cgroup cpuset -ocpuset
> /dev/cgroup
> 
> in which case ns would not be mounted.  But note, we
> DO NOT
> want you to have ns mounted :)
> 
> > I rebooted machine,
> > based on 2.6.32 kernel.
> > 
> > Then,
> > 
> > [host:~]$ mkdir /dev/cgroup
> > [host:~]$ mount -t cgroup cpuset -ocpuset,ns
> /dev/cgroup
> > [host:~]$ ps aux | grep libvirt
> > root       575 
> 0.6  0.9  88816  2216 ?     
>   Sl   17:28   0:00
> myproc --daemon
> > root       654 
> 0.0  0.2   4044   664
> ttyS0   
> S+   17:29   0:00 grep
> libvirt
> > [host:~]$ mkdir /dev/cgroup/hello
> > [host:~]$ cat /dev/cgroup/hello/tasks
> > [host:~]$ echo 0 > /dev/cgroup/hello/cpuset.cpus
> > [host:~]$ echo 0 > /dev/cgroup/hello/cpuset.mems
> > [host:~]$ echo 575 > /dev/cgroup/hello/tasks
> > [host:~]$ cat /dev/cgroup/hello/tasks
> > 575
> > [host:~]$ id
> > uid=0(root) gid=0(root) groups=0(root)
> > [host:~]$
> > 
> > Now, I try to move the task out - the parent/root:
> > 
> > [host:~]$ echo 575 > /dev/cgroup/tasks
> > -bash: echo: write error: Operation not permitted
> > 
> > 
> > Any thoughts !?
> 
> Yes, ns cgroup is forbidding you from moving back :) 
> Mount without it.
> 
> -serge
>