From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758758AbZLPPNw (ORCPT ); Wed, 16 Dec 2009 10:13:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758632AbZLPPNv (ORCPT ); Wed, 16 Dec 2009 10:13:51 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:49002 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758620AbZLPPNv (ORCPT ); Wed, 16 Dec 2009 10:13:51 -0500 Date: Wed, 16 Dec 2009 07:13:45 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, 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, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com Subject: Re: [PATCH RFC tip/core/rcu 15/18] rcu: give different levels of the rcu_node hierarchy distinct lockdep names Message-ID: <20091216151345.GB6744@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20091215230213.GA9093@linux.vnet.ibm.com> <1260959160.17860.39.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1260959160.17860.39.camel@laptop> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 16, 2009 at 11:26:00AM +0100, Peter Zijlstra wrote: > On Tue, 2009-12-15 at 15:02 -0800, Paul E. McKenney wrote: > > From: Paul E. McKenney > > > > Proposed for 2.6.34, not for inclusion. > > > > Previously, each level of the rcu_node hierarchy had the same rather > > unimaginative name: "&rcu_node_class[i]". This makes lockdep diagnostics > > involving these lockdep classes less helpful than would be nice. This > > patch fixes this by giving each level of the rcu_node hierarchy a distinct > > name: "rcu_node_level_0", "rcu_node_level_1", and so on. > > > > Signed-off-by: Paul E. McKenney > > --- > > kernel/rcutree.c | 9 ++++++++- > > 1 files changed, 8 insertions(+), 1 deletions(-) > > > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > > index 0a4c328..a6e45f6 100644 > > --- a/kernel/rcutree.c > > +++ b/kernel/rcutree.c > > @@ -1811,11 +1811,17 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp) > > */ > > static void __init rcu_init_one(struct rcu_state *rsp) > > { > > + static char *buf[] = { "rcu_node_level_0", > > + "rcu_node_level_1", > > + "rcu_node_level_2", > > + "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ > > int cpustride = 1; > > int i; > > int j; > > struct rcu_node *rnp; > > > > + WARN_ON_ONCE(MAX_RCU_LVLS > 4); /* Fix buf[] initialization! */ > > So you're going to WARN here, > > > /* Initialize the level-tracking arrays. */ > > > > for (i = 1; i < NUM_RCU_LVLS; i++) > > @@ -1829,7 +1835,8 @@ static void __init rcu_init_one(struct rcu_state *rsp) > > rnp = rsp->level[i]; > > for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { > > spin_lock_init(&rnp->lock); > > - lockdep_set_class(&rnp->lock, &rcu_node_class[i]); > > + lockdep_set_class_and_name(&rnp->lock, > > + &rcu_node_class[i], buf[i]); > > and segfault here because i overruns its bounds? Might or might not, depending on memory layout. > Might as well BUG_ON then. I will give BUILD_BUG_ON() a try, but with the array size computed at compile time as you suggest elsewhere. Thanx, Paul