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Subject[PATCH 2/9] cgroup: Use rculist ops for cgroup->children
Date
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>
---
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


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