lkml.org 
[lkml]   [2008]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH -v2] freezer_cg: disable writing freezer.state of root cgroup
From
On Wed, Nov 5, 2008 at 5:18 PM, Li Zefan <lizf@cn.fujitsu.com> wrote:
> With this change, control file 'freezer.state' doesn't exist in root
> cgroup, making root cgroup unfreezable.
>
> I think it's reasonable to disallow freeze tasks in the root cgroup.
> And then we can avoid fork overhead when freezer subsystem is
> compiled but not used.
>
> Also make writing invalid value to freezer.state returns EINVAL
> rather than EIO. This is more consistent with other cgroup subsystem.
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

Acked-by: Paul Menage <menage@google.com>

I might use the term "non-freezable" rather than "unfreezable".

Thanks,

Paul

> ---
>
> patch is based on freezer_cg-remove-task_lock-from-freezer_fork.patch
>
> ---
> Documentation/cgroups/freezer-subsystem.txt | 3 +++
> kernel/cgroup_freezer.c | 11 ++++++++++-
> 2 files changed, 13 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/cgroups/freezer-subsystem.txt b/Documentation/cgroups/freezer-subsystem.txt
> index c50ab58..91572b9 100644
> --- a/Documentation/cgroups/freezer-subsystem.txt
> +++ b/Documentation/cgroups/freezer-subsystem.txt
> @@ -54,6 +54,9 @@ freezer.state. Writing "FROZEN" to the state file will freeze all tasks in the
> cgroup. Subsequently writing "THAWED" will unfreeze the tasks in the cgroup.
> Reading will return the current state.
>
> +Note freezer.state doesn't exist in root cgroup, which means root cgroup
> +is unfreezable.
> +
> * Examples of usage :
>
> # mkdir /containers/freezer
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index 6605907..cf3fce9 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -192,6 +192,13 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
> */
> freezer = task_freezer(task);
>
> + /*
> + * The root cgroup is unfreezable, so we can skip the
> + * following check.
> + */
> + if (!freezer->css.cgroup->parent)
> + return;
> +
> spin_lock_irq(&freezer->lock);
> BUG_ON(freezer->state == CGROUP_FROZEN);
>
> @@ -335,7 +342,7 @@ static int freezer_write(struct cgroup *cgroup,
> else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
> goal_state = CGROUP_FROZEN;
> else
> - return -EIO;
> + return -EINVAL;
>
> if (!cgroup_lock_live_group(cgroup))
> return -ENODEV;
> @@ -354,6 +361,8 @@ static struct cftype files[] = {
>
> static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
> {
> + if (!cgroup->parent)
> + return 0;
> return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
> }
>
> --
> 1.5.4.rc3
>
>


\
 
 \ /
  Last update: 2008-11-06 02:27    [W:0.056 / U:1.784 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site