From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756703Ab2GQU7K (ORCPT ); Tue, 17 Jul 2012 16:59:10 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:58929 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756617Ab2GQU7I (ORCPT ); Tue, 17 Jul 2012 16:59:08 -0400 Date: Tue, 17 Jul 2012 13:58:56 -0700 From: "Paul E. McKenney" To: Fengguang Wu Cc: Josh Triplett , Lai Jiangshan , LKML , Steven Rostedt Subject: Re: rcu_dyntick and suspicious RCU usage Message-ID: <20120717205856.GF11150@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120709135637.GA26040@localhost> <20120709145724.GA27095@localhost> <20120710044700.GA9462@localhost> <20120711074924.GD3819@linux.vnet.ibm.com> <20120712164308.GA31584@linux.vnet.ibm.com> <20120712165738.GA21630@localhost> <20120712170242.GB31396@linux.vnet.ibm.com> <20120713091230.GA20208@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120713091230.GA20208@localhost> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12071720-6148-0000-0000-000007BF4925 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 13, 2012 at 05:12:30PM +0800, Fengguang Wu wrote: > On Thu, Jul 12, 2012 at 10:02:42AM -0700, Paul E. McKenney wrote: > > On Fri, Jul 13, 2012 at 12:57:38AM +0800, Fengguang Wu wrote: > > > On Thu, Jul 12, 2012 at 09:43:08AM -0700, Paul E. McKenney wrote: > > > > On Wed, Jul 11, 2012 at 12:49:24AM -0700, Paul E. McKenney wrote: > > > > > On Tue, Jul 10, 2012 at 12:47:00PM +0800, Fengguang Wu wrote: > > > > > > Hi Paul, > > > > > > > > > > > > Fortunately this bug is bisectable and the first bad commit is: > > > > > > > > > > > > commit 9b2e4f1880b789be1f24f9684f7a54b90310b5c0 > > > > > > Author: Paul E. McKenney > > > > > > Date: Fri Sep 30 12:10:22 2011 -0700 > > > > > > > > > > > > rcu: Track idleness independent of idle tasks > > > > > > > > > > OK, there is a problem in TINY_RCU's handling of dyntick-idle: it > > > > > traces while in idle. The confusion on my part was that in TREE_RCU, > > > > > the nesting and dyntick-idle indication are different, while in > > > > > TINY_RCU they are one and the same. > > > > > > > > > > Does the following patch help? > > > > > > > > This one failed in my testing. Please see the end for the fixed > > > > version, with on small but important change. > > > > > > It worked, thanks! > > > > > > Tested-by: Fengguang Wu > > > > Very good! (And please ignore my resend of the same patch.) > > > > I will queue this. > > Will you recommend it for -stable? It impacts 3.3/3.4. I tested it on > 3.4 and it works fine. However for 3.3, the patch cannot apply cleanly. If someone hits it in a real workload, I might consider it. I currently have it queued for 3.7. Thanx, Paul