From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752200AbbAMJgb (ORCPT ); Tue, 13 Jan 2015 04:36:31 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:42677 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752079AbbAMJg3 (ORCPT ); Tue, 13 Jan 2015 04:36:29 -0500 Date: Tue, 13 Jan 2015 01:36:18 -0800 From: "Paul E. McKenney" To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, Josh Triplett , Steven Rostedt , Mathieu Desnoyers Subject: Re: [PATCH] rcu_tree: avoid touch rnp->completed when starts a new GP Message-ID: <20150113093618.GI9719@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1421134234-3418-1-git-send-email-laijs@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1421134234-3418-1-git-send-email-laijs@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15011309-0005-0000-0000-000007FA4384 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 13, 2015 at 03:30:34PM +0800, Lai Jiangshan wrote: > In rcu_gp_init(), rnp->completed equals to rsp->completed in THEORY, > we don't need to touch it normally. If something goes wrong, > it will complain and fixup rnp->completed and avoid oops. > > Signed-off-by: Lai Jiangshan Queued for 3.21, thank you! Thanx, Paul > --- > kernel/rcu/tree.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 7680fc2..ea6dc28 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1639,8 +1639,8 @@ static int rcu_gp_init(struct rcu_state *rsp) > rcu_preempt_check_blocked_tasks(rnp); > rnp->qsmask = rnp->qsmaskinit; > ACCESS_ONCE(rnp->gpnum) = rsp->gpnum; > - WARN_ON_ONCE(rnp->completed != rsp->completed); > - ACCESS_ONCE(rnp->completed) = rsp->completed; > + if (WARN_ON_ONCE(rnp->completed != rsp->completed)) > + ACCESS_ONCE(rnp->completed) = rsp->completed; > if (rnp == rdp->mynode) > (void)__note_gp_changes(rsp, rnp, rdp); > rcu_preempt_boost_start_gp(rnp); > -- > 2.1.0 >