Messages in this thread Patch in this message | | | Date | Mon, 8 Apr 2013 14:35:34 +0800 | From | Li Zefan <> | Subject | [PATCH 10/12] memcg: don't need to get a reference to the parent |
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The cgroup core guarantees it's always safe to access the parent.
v2: - added a comment in mem_cgroup_put() as suggested by Michal - removed mem_cgroup_get(), otherwise gcc will warn that it's not used
Signed-off-by: Li Zefan <lizefan@huawei.com> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memcontrol.c | 19 +++---------------- 1 file changed, 3 insertions(+), 16 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 7fdd69d..9ca5a99 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -501,7 +501,6 @@ enum res_type { */ static DEFINE_MUTEX(memcg_create_mutex); -static void mem_cgroup_get(struct mem_cgroup *memcg); static void mem_cgroup_put(struct mem_cgroup *memcg); static inline @@ -6125,19 +6124,10 @@ static void free_rcu(struct rcu_head *rcu_head) schedule_work(&memcg->work_freeing); } -static void mem_cgroup_get(struct mem_cgroup *memcg) -{ - atomic_inc(&memcg->refcnt); -} - static void __mem_cgroup_put(struct mem_cgroup *memcg, int count) { - if (atomic_sub_and_test(count, &memcg->refcnt)) { - struct mem_cgroup *parent = parent_mem_cgroup(memcg); + if (atomic_sub_and_test(count, &memcg->refcnt)) call_rcu(&memcg->rcu_freeing, free_rcu); - if (parent) - mem_cgroup_put(parent); - } } static void mem_cgroup_put(struct mem_cgroup *memcg) @@ -6239,12 +6229,9 @@ mem_cgroup_css_online(struct cgroup *cont) res_counter_init(&memcg->kmem, &parent->kmem); /* - * We increment refcnt of the parent to ensure that we can - * safely access it on res_counter_charge/uncharge. - * This refcnt will be decremented when freeing this - * mem_cgroup(see mem_cgroup_put). + * No need to take a reference to the parent because cgroup + * core guarantees its existence. */ - mem_cgroup_get(parent); } else { res_counter_init(&memcg->res, NULL); res_counter_init(&memcg->memsw, NULL); -- 1.8.0.2
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