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| author |   Tejun Heo <tj@kernel.org> | 2013-01-07 08:49:33 -0800 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2013-01-07 08:50:28 -0800 |
| commit | 12a9d2fef1d35770d3cdc2cd1faabb83c45bc0fa (patch) | |
| tree | a7c50e81a638a156ce8d4f41dcab273397e6e474 | |
| parent | cgroup: remove unused dummy cgroup_fork_callbacks() (diff) | |
| download | linux-dev-12a9d2fef1d35770d3cdc2cd1faabb83c45bc0fa.tar.xz linux-dev-12a9d2fef1d35770d3cdc2cd1faabb83c45bc0fa.zip | |
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.h | 1 | ||||
| -rw-r--r-- | kernel/cgroup.c | 26 |
2 files changed, 27 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 942e68705577..8118a3120378 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 4855892798fd..6643f7053454 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; |