From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753478AbbCIIgF (ORCPT ); Mon, 9 Mar 2015 04:36:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51669 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753345AbbCIIe2 (ORCPT ); Mon, 9 Mar 2015 04:34:28 -0400 From: Alexander Gordeev To: linux-kernel@vger.kernel.org Cc: Alexander Gordeev , "Paul E. McKenney" Subject: [PATCH 05/10] rcu: Limit rcu_state::levelcnt[] to RCU_NUM_LVLS items Date: Mon, 9 Mar 2015 09:34:09 +0100 Message-Id: <8c4fac4157014a0dcd3a22b60f0e4aaf03e28e50.1425889432.git.agordeev@redhat.com> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Variable rcu_num_lvls is limited by RCU_NUM_LVLS macro. In turn, rcu_state::levelcnt[] array is never accessed beyond rcu_num_lvls. Thus, rcu_state::levelcnt[] is safe to limit to RCU_NUM_LVLS items. Since rcu_num_lvls could be changed during boot (as result of rcutree.rcu_fanout_leaf kernel parameter update) one might assume a new value could overflow the value of RCU_NUM_LVLS. However, that is not the case, since leaf-level fanout is only permitted to increase, resulting in rcu_num_lvls possibly to decrease. Cc: "Paul E. McKenney" Signed-off-by: Alexander Gordeev --- kernel/rcu/tree.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index dd5ce40..f358a83 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -421,7 +421,7 @@ do { \ struct rcu_state { struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ struct rcu_node *level[RCU_NUM_LVLS]; /* Hierarchy levels. */ - u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ + u32 levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */ u8 levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ u8 flavor_mask; /* bit in flavor mask. */ struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ -- 1.8.3.1