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cgroup: implement cgroup_rightmost_descendant()

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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>
This commit is contained in:
Tejun Heo 2013-01-07 08:49:33 -08:00
parent d5b1fe68ba
commit 12a9d2fef1
2 changed files with 27 additions and 0 deletions
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1
include/linux/cgroup.h
View file

@ -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

26
kernel/cgroup.c
View file

@ -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;