From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752385AbZHTEV1 (ORCPT ); Thu, 20 Aug 2009 00:21:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752139AbZHTEV0 (ORCPT ); Thu, 20 Aug 2009 00:21:26 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:41309 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752101AbZHTEV0 (ORCPT ); Thu, 20 Aug 2009 00:21:26 -0400 Date: Wed, 19 Aug 2009 21:21:24 -0700 From: "Paul E. McKenney" To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com, josht@linux.vnet.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, hugh.dickins@tiscali.co.uk, benh@kernel.crashing.org Subject: Re: [PATCH -tip/core/rcu 3/6] Simplify RCU CPU-hotplug notification Message-ID: <20090820042124.GC6847@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090815165153.GA8886@linux.vnet.ibm.com> <4A8CCAE4.4030707@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A8CCAE4.4030707@cn.fujitsu.com> 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 Thu, Aug 20, 2009 at 12:02:44PM +0800, Lai Jiangshan wrote: > Paul E. McKenney wrote: > > From: Paul E. McKenney > > > > Use the new cpu_notifier() API to simplify RCU's CPU-hotplug > > notifiers, collapsing down to a single such notifier. This > > makes it trivial to provide the notifier-ordering guarantee > > that rcu_barrier() depends on. Also remove redundant > > open_softirq() calls from Hierarchical RCU notifier. > > > > Signed-off-by: Paul E. McKenney > > --- > > kernel/rcupdate.c | 16 +++++++++++++++- > > kernel/rcupreempt.c | 25 ++----------------------- > > kernel/rcutree.c | 17 +++++------------ > > 3 files changed, 22 insertions(+), 36 deletions(-) > > > > diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c > > index eae29c2..8df1156 100644 > > --- a/kernel/rcupdate.c > > +++ b/kernel/rcupdate.c > > @@ -217,9 +217,13 @@ static void rcu_migrate_callback(struct rcu_head *notused) > > wake_up(&rcu_migrate_wq); > > } > > > > +extern int rcu_cpu_notify(struct notifier_block *self, > > + unsigned long action, void *hcpu); > > + > > static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, > > unsigned long action, void *hcpu) > > { > > + rcu_cpu_notify(self, action, hcpu); > > if (action == CPU_DYING) { > > /* > > * preempt_disable() in on_each_cpu() prevents stop_machine(), > > @@ -244,8 +248,18 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, > > > > void __init rcu_init(void) > > { > > + int i; > > + > > __rcu_init(); > > - hotcpu_notifier(rcu_barrier_cpu_hotplug, 0); > > + cpu_notifier(rcu_barrier_cpu_hotplug, 0); > > + > > + /* > > + * We don't need protection against CPU-hotplug here because > > + * this is called early in boot, before either interrupts > > + * or the scheduler are operational. > > + */ > > + for_each_online_cpu(i) > > + rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i); > > I think, > There is only one cpu in cpu online map at early boot time, > it is the current cpu. Indeed there is. But I wouldn't put it past the fast-boot guys to parallelize early boot. ;-) Thanx, Paul