From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753926Ab2BBBCA (ORCPT ); Wed, 1 Feb 2012 20:02:00 -0500 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:35337 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753341Ab2BBBB7 (ORCPT ); Wed, 1 Feb 2012 20:01:59 -0500 X-Originating-IP: 217.70.178.139 X-Originating-IP: 50.43.15.19 Date: Wed, 1 Feb 2012 17:01:46 -0800 From: Josh Triplett 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, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, "Paul E. McKenney" Subject: Re: [PATCH RFC tip/core/rcu 04/41] rcu: Add diagnostic for misaligned rcu_head structures Message-ID: <20120202010146.GF29058@leaf> References: <20120201194131.GA10028@linux.vnet.ibm.com> <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> <1328125319-5205-4-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1328125319-5205-4-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 01, 2012 at 11:41:22AM -0800, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > The push for energy efficiency will require that RCU tag rcu_head > structures to indicate whether or not their invocation is time critical. > This tagging is best carried out in the bottom bits of the ->next > pointers in the rcu_head structures. This tagging requires that the > rcu_head structures be properly aligned, so this commit adds the required > diagnostics. > > Signed-off-by: Paul E. McKenney > Signed-off-by: Paul E. McKenney > --- > kernel/rcutree.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index d0f8e64..4655f3e 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1707,6 +1707,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), > unsigned long flags; > struct rcu_data *rdp; > > + WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ > debug_rcu_head_queue(head); Upon further checking: static inline void debug_rcu_head_queue(struct rcu_head *head) { WARN_ON_ONCE((unsigned long)head & 0x3); :) - Josh Triplett