From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761289AbZLPK0o (ORCPT ); Wed, 16 Dec 2009 05:26:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761244AbZLPK0m (ORCPT ); Wed, 16 Dec 2009 05:26:42 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:41666 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761283AbZLPK0k (ORCPT ); Wed, 16 Dec 2009 05:26:40 -0500 Subject: Re: [PATCH RFC tip/core/rcu 15/18] rcu: give different levels of the rcu_node hierarchy distinct lockdep names From: Peter Zijlstra To: "Paul E. McKenney" 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 In-Reply-To: <12609181611666-git-send-email-> References: <20091215230213.GA9093@linux.vnet.ibm.com> <12609181611666-git-send-email-> Content-Type: text/plain; charset="UTF-8" Date: Wed, 16 Dec 2009 11:26:00 +0100 Message-ID: <1260959160.17860.39.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 as well BUG_ON then.