From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932157AbbGQWcK (ORCPT ); Fri, 17 Jul 2015 18:32:10 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:56854 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755057AbbGQWbZ (ORCPT ); Fri, 17 Jul 2015 18:31:25 -0400 X-Helo: d03dlp02.boulder.ibm.com X-MailFrom: paulmck@linux.vnet.ibm.com X-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, Alexander Gordeev , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 11/12] rcu: Shut up bogus gcc array bounds warning Date: Fri, 17 Jul 2015 15:31:02 -0700 Message-Id: <1437172263-15466-11-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1437172263-15466-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150717223041.GA14464@linux.vnet.ibm.com> <1437172263-15466-1-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15071722-0025-0000-0000-0000173C054C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexander Gordeev Because gcc does not realize a loop would not be entered ever (i.e. in case of rcu_num_lvls == 1): for (i = 1; i < rcu_num_lvls; i++) rsp->level[i] = rsp->level[i - 1] + levelcnt[i - 1]; some compiler (pre- 5.x?) versions give a bogus warning: kernel/rcu/tree.c: In function ‘rcu_init_one.isra.55’: kernel/rcu/tree.c:4108:13: warning: array subscript is above array bounds [-Warray-bounds] rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; ^ Fix that warning by adding an extra item to rcu_state::level[] array. Once the bogus warning is fixed in gcc and kernel drops support of older versions, the dummy item may be removed from the array. Cc: "Paul E. McKenney" Suggested-by: "Paul E. McKenney" Signed-off-by: Alexander Gordeev Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 581f8d3c5b28..faee5242d6ff 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -443,7 +443,9 @@ do { \ */ struct rcu_state { struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ - struct rcu_node *level[RCU_NUM_LVLS]; /* Hierarchy levels. */ + struct rcu_node *level[RCU_NUM_LVLS + 1]; + /* Hierarchy levels (+1 to */ + /* shut bogus gcc warning) */ u8 flavor_mask; /* bit in flavor mask. */ struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ void (*call)(struct rcu_head *head, /* call_rcu() flavor. */ -- 1.8.1.5