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authorTejun Heo <tj@kernel.org>2013-01-07 08:49:33 -0800
committerTejun Heo <tj@kernel.org>2013-01-07 08:50:28 -0800
commit12a9d2fef1d35770d3cdc2cd1faabb83c45bc0fa (patch)
treea7c50e81a638a156ce8d4f41dcab273397e6e474
parentd5b1fe68baa7213f198e5be8cd1a1037258ab2c8 (diff)
downloadvexpress-lsk-12a9d2fef1d35770d3cdc2cd1faabb83c45bc0fa.tar.gz
cgroup: implement cgroup_rightmost_descendant()
Implement cgroup_rightmost_descendant() which returns the right most descendant of the specified cgroup. This can be used to skip the cgroup's subtree while iterating with cgroup_for_each_descendant_pre(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizefan@huawei.com>
-rw-r--r--include/linux/cgroup.h1
-rw-r--r--kernel/cgroup.c26
2 files changed, 27 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 942e6870557..8118a312037 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -558,6 +558,7 @@ static inline struct cgroup* task_cgroup(struct task_struct *task,
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
struct cgroup *cgroup);
+struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
/**
* cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4855892798f..6643f705345 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3017,6 +3017,32 @@ struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);
+/**
+ * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
+ * @pos: cgroup of interest
+ *
+ * Return the rightmost descendant of @pos. If there's no descendant,
+ * @pos is returned. This can be used during pre-order traversal to skip
+ * subtree of @pos.
+ */
+struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)
+{
+ struct cgroup *last, *tmp;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ do {
+ last = pos;
+ /* ->prev isn't RCU safe, walk ->next till the end */
+ pos = NULL;
+ list_for_each_entry_rcu(tmp, &last->children, sibling)
+ pos = tmp;
+ } while (pos);
+
+ return last;
+}
+EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);
+
static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
{
struct cgroup *last;