From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756063Ab0ECSxd (ORCPT ); Mon, 3 May 2010 14:53:33 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:41093 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755450Ab0ECSx1 (ORCPT ); Mon, 3 May 2010 14:53:27 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, Li Zefan , "Paul E. McKenney" Subject: [PATCH tip/core/urgent 05/10] cgroup: Fix an RCU warning in alloc_css_id() Date: Mon, 3 May 2010 11:53:14 -0700 Message-Id: <1272912799-17859-5-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.0 In-Reply-To: <20100503185253.GA17672@linux.vnet.ibm.com> References: <20100503185253.GA17672@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Li Zefan With CONFIG_PROVE_RCU=y, a warning can be triggered: # mount -t cgroup -o memory xxx /mnt # mkdir /mnt/0 ... kernel/cgroup.c:4442 invoked rcu_dereference_check() without protection! ... This is a false-positive. It's safe to directly access parent_css->id. Signed-off-by: Li Zefan Signed-off-by: Paul E. McKenney --- kernel/cgroup.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 4ca928d..3a53c77 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4561,13 +4561,13 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent, { int subsys_id, i, depth = 0; struct cgroup_subsys_state *parent_css, *child_css; - struct css_id *child_id, *parent_id = NULL; + struct css_id *child_id, *parent_id; subsys_id = ss->subsys_id; parent_css = parent->subsys[subsys_id]; child_css = child->subsys[subsys_id]; - depth = css_depth(parent_css) + 1; parent_id = parent_css->id; + depth = parent_id->depth; child_id = get_new_cssid(ss, depth); if (IS_ERR(child_id)) -- 1.7.0