From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755826Ab2IBBpy (ORCPT ); Sat, 1 Sep 2012 21:45:54 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:38031 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754585Ab2IBBpx (ORCPT ); Sat, 1 Sep 2012 21:45:53 -0400 X-Originating-IP: 217.70.178.133 X-Originating-IP: 50.43.46.74 Date: Sat, 1 Sep 2012 18:45:45 -0700 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, sbw@mit.edu, patches@linaro.org, "Paul E. McKenney" Subject: Re: [PATCH tip/core/rcu 05/23] rcu: Prevent offline CPUs from executing RCU core code Message-ID: <20120902014545.GE5713@leaf> References: <20120830181811.GA29154@linux.vnet.ibm.com> <1346350718-30937-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346350718-30937-5-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: <1346350718-30937-5-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 Thu, Aug 30, 2012 at 11:18:20AM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > Earlier versions of RCU invoked the RCU core from the CPU_DYING notifier > in order to note a quiescent state for the outgoing CPU. Because the > CPU is marked "offline" during the execution of the CPU_DYING notifiers, > the RCU core had to tolerate being invoked from an offline CPU. However, > commit b1420f1c (Make rcu_barrier() less disruptive) left only tracing > code in the CPU_DYING notifier, so the RCU core need no longer execute > on offline CPUs. This commit therefore enforces this restriction. > > Signed-off-by: Paul E. McKenney > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > kernel/rcutree.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 300aba6..84a6f55 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1892,6 +1892,8 @@ static void rcu_process_callbacks(struct softirq_action *unused) > { > struct rcu_state *rsp; > > + if (cpu_is_offline(smp_processor_id())) > + return; > trace_rcu_utilization("Start RCU core"); > for_each_rcu_flavor(rsp) > __rcu_process_callbacks(rsp); > -- > 1.7.8 >