From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751920Ab0C1ERa (ORCPT ); Sun, 28 Mar 2010 00:17:30 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:58896 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751185Ab0C1ER2 (ORCPT ); Sun, 28 Mar 2010 00:17:28 -0400 Date: Sat, 27 Mar 2010 21:17:24 -0700 From: "Paul E. McKenney" To: Lai Jiangshan Cc: Ingo Molnar , LKML Subject: Re: [PATCH] rcu: remove lock acquirement when very eary boot Message-ID: <20100328041724.GR2343@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <4BAEC985.6020302@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BAEC985.6020302@cn.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 28, 2010 at 11:14:13AM +0800, Lai Jiangshan wrote: > > cleanup: remove lock acquirement when very eary boot This is indeed a safe change, however, I am keeping this lock acquisition and release for documentation purposes. Call me paranoid, but... Thanx, Paul > Signed-off-by: Lai Jiangshan > --- > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 112edb5..e6014e1 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1646,13 +1646,10 @@ EXPORT_SYMBOL_GPL(rcu_barrier_sched); > static void __init > rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) > { > - unsigned long flags; > int i; > struct rcu_data *rdp = rsp->rda[cpu]; > - struct rcu_node *rnp = rcu_get_root(rsp); > > /* Set up local state, ensuring consistent view of global state. */ > - raw_spin_lock_irqsave(&rnp->lock, flags); > rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); > rdp->nxtlist = NULL; > for (i = 0; i < RCU_NEXT_SIZE; i++) > @@ -1662,7 +1659,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) > rdp->dynticks = &per_cpu(rcu_dynticks, cpu); > #endif /* #ifdef CONFIG_NO_HZ */ > rdp->cpu = cpu; > - raw_spin_unlock_irqrestore(&rnp->lock, flags); > } > > /* >