From 692e89abd154b04d212dce0c18a449bda15aac04 Mon Sep 17 00:00:00 2001 From: Glauber Costa Date: Fri, 22 Feb 2013 16:34:56 -0800 Subject: [PATCH] memcg: increment static branch right after limit set We were deferring the kmemcg static branch increment to a later time, due to a nasty dependency between the cpu_hotplug lock, taken by the jump label update, and the cgroup_lock. Now we no longer take the cgroup lock, and we can save ourselves the trouble. Signed-off-by: Glauber Costa Acked-by: Michal Hocko Cc: Tejun Heo Cc: Hiroyuki Kamezawa Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 31 +++++++------------------------ 1 file changed, 7 insertions(+), 24 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 46cdaef78b01..f4f41c36e703 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4974,8 +4974,6 @@ static int memcg_update_kmem_limit(struct cgroup *cont, u64 val) { int ret = -EINVAL; #ifdef CONFIG_MEMCG_KMEM - bool must_inc_static_branch = false; - struct mem_cgroup *memcg = mem_cgroup_from_cont(cont); /* * For simplicity, we won't allow this to be disabled. It also can't @@ -5004,7 +5002,13 @@ static int memcg_update_kmem_limit(struct cgroup *cont, u64 val) res_counter_set_limit(&memcg->kmem, RESOURCE_MAX); goto out; } - must_inc_static_branch = true; + static_key_slow_inc(&memcg_kmem_enabled_key); + /* + * setting the active bit after the inc will guarantee no one + * starts accounting before all call sites are patched + */ + memcg_kmem_set_active(memcg); + /* * kmem charges can outlive the cgroup. In the case of slab * pages, for instance, a page contain objects from various @@ -5017,27 +5021,6 @@ static int memcg_update_kmem_limit(struct cgroup *cont, u64 val) out: mutex_unlock(&set_limit_mutex); mutex_unlock(&memcg_create_mutex); - - /* - * We are by now familiar with the fact that we can't inc the static - * branch inside cgroup_lock. See disarm functions for details. A - * worker here is overkill, but also wrong: After the limit is set, we - * must start accounting right away. Since this operation can't fail, - * we can safely defer it to here - no rollback will be needed. - * - * The boolean used to control this is also safe, because - * KMEM_ACCOUNTED_ACTIVATED guarantees that only one process will be - * able to set it to true; - */ - if (must_inc_static_branch) { - static_key_slow_inc(&memcg_kmem_enabled_key); - /* - * setting the active bit after the inc will guarantee no one - * starts accounting before all call sites are patched - */ - memcg_kmem_set_active(memcg); - } - #endif return ret; } -- 2.30.2