From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id B5B926B004F for ; Thu, 19 Jan 2012 15:52:01 -0500 (EST) Received: by iadj38 with SMTP id j38so500046iad.14 for ; Thu, 19 Jan 2012 12:52:01 -0800 (PST) Date: Thu, 19 Jan 2012 12:51:47 -0800 (PST) From: Hugh Dickins Subject: [PATCH 3/3] memcg: let css_get_next() rely upon rcu_read_lock() In-Reply-To: Message-ID: References: <1326958401.1113.22.camel@edumazet-laptop> <1326979818.2249.12.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Eric Dumazet , Li Zefan , Andrew Morton , Manfred Spraul , KAMEZAWA Hiroyuki , Johannes Weiner , Ying Han , Greg Thelen , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Remove lock and unlock around css_get_next()'s call to idr_get_next(). memcg iterators (only users of css_get_next) already did rcu_read_lock(), and its comment demands that; but add a WARN_ON_ONCE to make sure of it. Signed-off-by: Hugh Dickins Acked-by: KAMEZAWA Hiroyuki Acked-by: Li Zefan --- kernel/cgroup.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- 3.2.0+.orig/kernel/cgroup.c 2012-01-19 12:16:04.000000000 -0800 +++ 3.2.0+/kernel/cgroup.c 2012-01-19 12:22:55.188244820 -0800 @@ -5087,6 +5087,8 @@ css_get_next(struct cgroup_subsys *ss, i return NULL; BUG_ON(!ss->use_id); + WARN_ON_ONCE(!rcu_read_lock_held()); + /* fill start point for scan */ tmpid = id; while (1) { @@ -5094,10 +5096,7 @@ css_get_next(struct cgroup_subsys *ss, i * scan next entry from bitmap(tree), tmpid is updated after * idr_get_next(). */ - spin_lock(&ss->id_lock); tmp = idr_get_next(&ss->idr, &tmpid); - spin_unlock(&ss->id_lock); - if (!tmp) break; if (tmp->depth >= depth && tmp->stack[depth] == rootid) { -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org