From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752008AbaGWMVU (ORCPT ); Wed, 23 Jul 2014 08:21:20 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:58398 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750800AbaGWMVT (ORCPT ); Wed, 23 Jul 2014 08:21:19 -0400 Date: Wed, 23 Jul 2014 05:21:12 -0700 From: "Paul E. McKenney" To: Pranith Kumar Cc: Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , "open list:READ-COPY UPDATE..." Subject: Re: [PATCH 09/16] rcu: Remove redundant check for online cpu Message-ID: <20140723122112.GJ11241@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1406092194-13004-1-git-send-email-bobby.prani@gmail.com> <1406092194-13004-10-git-send-email-bobby.prani@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1406092194-13004-10-git-send-email-bobby.prani@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14072312-1344-0000-0000-0000030227A1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 23, 2014 at 01:09:46AM -0400, Pranith Kumar wrote: > There are two checks for an online CPU if two if() conditions. This commit > simplies this by replacing it with only one check for the online CPU. > > Signed-off-by: Pranith Kumar I admit that it is very early in the morning my time, but I don't see this change as preserving the semantics in all cases. Please recheck your changes to the second check. Thanx, Paul > --- > kernel/rcu/tree.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 5dcbf36..8d598a2 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2602,15 +2602,18 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, > { > bool needwake; > > + if (!cpu_online(smp_processor_id())) > + return; > + > /* > * If called from an extended quiescent state, invoke the RCU > * core in order to force a re-evaluation of RCU's idleness. > */ > - if (!rcu_is_watching() && cpu_online(smp_processor_id())) > + if (!rcu_is_watching()) > invoke_rcu_core(); > > - /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ > - if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) > + /* If interrupts were disabled, don't invoke RCU core. */ > + if (irqs_disabled_flags(flags)) > return; > > /* > -- > 2.0.0.rc2 >