From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx104.postini.com [74.125.245.104]) by kanga.kvack.org (Postfix) with SMTP id 0937F6B02E3 for ; Fri, 3 May 2013 12:49:51 -0400 (EDT) Received: by mail-pb0-f43.google.com with SMTP id md12so996212pbc.2 for ; Fri, 03 May 2013 09:49:51 -0700 (PDT) Date: Fri, 3 May 2013 09:49:49 -0700 (PDT) From: David Rientjes Subject: [patch] mm, memcg: don't take task_lock in task_in_mem_cgroup Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: KAMEZAWA Hiroyuki , Johannes Weiner , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org For processes that have detached their mm's, task_in_mem_cgroup() unnecessarily takes task_lock() when rcu_read_lock() is all that is necessary to call mem_cgroup_from_task(). While we're here, switch task_in_mem_cgroup() to return bool. Signed-off-by: David Rientjes --- include/linux/memcontrol.h | 9 +++++---- mm/memcontrol.c | 11 ++++++----- 2 files changed, 11 insertions(+), 9 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -77,7 +77,8 @@ extern void mem_cgroup_uncharge_cache_page(struct page *page); bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, struct mem_cgroup *memcg); -int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg); +bool task_in_mem_cgroup(struct task_struct *task, + const struct mem_cgroup *memcg); extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page); extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p); @@ -273,10 +274,10 @@ static inline bool mm_match_cgroup(struct mm_struct *mm, return true; } -static inline int task_in_mem_cgroup(struct task_struct *task, - const struct mem_cgroup *memcg) +static inline bool task_in_mem_cgroup(struct task_struct *task, + const struct mem_cgroup *memcg) { - return 1; + return true; } static inline struct cgroup_subsys_state diff --git a/mm/memcontrol.c b/mm/memcontrol.c --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1443,11 +1443,12 @@ static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, return ret; } -int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg) +bool task_in_mem_cgroup(struct task_struct *task, + const struct mem_cgroup *memcg) { - int ret; struct mem_cgroup *curr = NULL; struct task_struct *p; + bool ret; p = find_lock_task_mm(task); if (p) { @@ -1459,14 +1460,14 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg) * killer still needs to detect if they have already been oom * killed to prevent needlessly killing additional tasks. */ - task_lock(task); + rcu_read_lock(); curr = mem_cgroup_from_task(task); if (curr) css_get(&curr->css); - task_unlock(task); + rcu_read_unlock(); } if (!curr) - return 0; + return false; /* * We should check use_hierarchy of "memcg" not "curr". Because checking * use_hierarchy of "curr" here make this function true if hierarchy is -- 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: email@kvack.org