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SubjectRe: [PATCH 2/9] cgroup: Use rculist ops for cgroup->children
On Sat 03-11-12 01:38:28, Tejun Heo wrote:
> Use RCU safe list operations for cgroup->children. This will be used
> to implement cgroup children / descendant walking which can be used by
> controllers.
>
> Note that cgroup_create() now puts a new cgroup at the end of the
> ->children list instead of head. This isn't strictly necessary but is
> done so that the iteration order is more conventional.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
> include/linux/cgroup.h | 1 +
> kernel/cgroup.c | 8 +++-----
> 2 files changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index b442122..90c33eb 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -12,6 +12,7 @@
> #include <linux/cpumask.h>
> #include <linux/nodemask.h>
> #include <linux/rcupdate.h>
> +#include <linux/rculist.h>
> #include <linux/cgroupstats.h>
> #include <linux/prio_heap.h>
> #include <linux/rwsem.h>
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index f05d992..cc5d2a0 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1650,7 +1650,6 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
>
> free_cg_links(&tmp_cg_links);
>
> - BUG_ON(!list_empty(&root_cgrp->sibling));
> BUG_ON(!list_empty(&root_cgrp->children));
> BUG_ON(root->number_of_cgroups != 1);
>
> @@ -1699,7 +1698,6 @@ static void cgroup_kill_sb(struct super_block *sb) {
>
> BUG_ON(root->number_of_cgroups != 1);
> BUG_ON(!list_empty(&cgrp->children));
> - BUG_ON(!list_empty(&cgrp->sibling));
>
> mutex_lock(&cgroup_mutex);
> mutex_lock(&cgroup_root_mutex);
> @@ -4053,7 +4051,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> }
> }
>
> - list_add(&cgrp->sibling, &cgrp->parent->children);
> + list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
> root->number_of_cgroups++;
>
> err = cgroup_create_dir(cgrp, dentry, mode);
> @@ -4084,7 +4082,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
>
> err_remove:
>
> - list_del(&cgrp->sibling);
> + list_del_rcu(&cgrp->sibling);
> root->number_of_cgroups--;
>
> err_destroy:
> @@ -4210,7 +4208,7 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
> raw_spin_unlock(&release_list_lock);
>
> /* delete this cgroup from parent->children */
> - list_del_init(&cgrp->sibling);
> + list_del_rcu(&cgrp->sibling);
>
> list_del_init(&cgrp->allcg_node);
>
> --
> 1.7.11.7
>

--
Michal Hocko
SUSE Labs


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