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authorJohannes Weiner <hannes@cmpxchg.org>2012-05-29 15:06:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-29 16:22:20 -0700
commit91c63734f6908425903aed69c04035592f18d398 (patch)
tree6790827ab915b17c63d5c39d8c72c47f3764f868 /mm/memcontrol.c
parent0ce72d4f7333248efbef1f3309770c7edb1b2625 (diff)
kernel: cgroup: push rcu read locking from css_is_ancestor() to callsite
Library functions should not grab locks when the callsites can do it, even if the lock nests like the rcu read-side lock does. Push the rcu_read_lock() from css_is_ancestor() to its single user, mem_cgroup_same_or_subtree() in preparation for another user that may already hold the rcu read-side lock. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 92675fe8a2ef..faad98e6d17d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1152,12 +1152,16 @@ struct lruvec *mem_cgroup_lru_move_lists(struct zone *zone,
static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
struct mem_cgroup *memcg)
{
- if (root_memcg != memcg) {
- return (root_memcg->use_hierarchy &&
- css_is_ancestor(&memcg->css, &root_memcg->css));
- }
+ bool ret;
- return true;
+ if (root_memcg == memcg)
+ return true;
+ if (!root_memcg->use_hierarchy)
+ return false;
+ rcu_read_lock();
+ ret = css_is_ancestor(&memcg->css, &root_memcg->css);
+ rcu_read_unlock();
+ return ret;
}
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)