Messages in this thread | | | Date | Thu, 4 Apr 2013 17:34:25 +0200 | From | Michal Hocko <> | Subject | Re: [RFC][PATCH 6/7] memcg: don't need to get a reference to the parent |
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On Wed 03-04-13 17:13:21, Li Zefan wrote: > The cgroup core guarantees it's always safe to access the parent. > > Signed-off-by: Li Zefan <lizefan@huawei.com>
I would just prefer if you put a comment into place where we used to take a reference to parent so that it is more obvious in the code. See bellow.
Acked-by: Michal Hocko <mhocko@suse.cz>
> --- > mm/memcontrol.c | 14 +------------- > 1 file changed, 1 insertion(+), 13 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ad576e8..45129cd 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6124,12 +6124,8 @@ static void mem_cgroup_get(struct mem_cgroup *memcg) > > 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) > @@ -6229,14 +6225,6 @@ mem_cgroup_css_online(struct cgroup *cont) > res_counter_init(&memcg->res, &parent->res); > res_counter_init(&memcg->memsw, &parent->memsw); > 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). > - */ > - mem_cgroup_get(parent);
Maybe a little note would be nice /* * No need to take reference to parent because cgroup * core guarantees its existence */ > } else { > res_counter_init(&memcg->res, NULL); > res_counter_init(&memcg->memsw, NULL); > -- > 1.8.0.2 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
-- Michal Hocko SUSE Labs
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