Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755229AbZISGz5 (ORCPT ); Sat, 19 Sep 2009 02:55:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754818AbZISGz4 (ORCPT ); Sat, 19 Sep 2009 02:55:56 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:50095 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754806AbZISGz4 (ORCPT ); Sat, 19 Sep 2009 02:55:56 -0400 Date: Sat, 19 Sep 2009 08:55:23 +0200 From: Ingo Molnar To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu Subject: Re: [PATCH tip/core/rcu 0/3] Cleanups/bugfixes for large systems and TREE_PREEMPT_RCU Message-ID: <20090919065523.GA17617@elte.hu> References: <20090918164955.GA22272@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090918164955.GA22272@linux.vnet.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1749 Lines: 39 * Paul E. McKenney wrote: > This set of patches does some cleanups and fixes a bug that prevents > TREE_PREEMPT_RCU from running reliably on large systems (more than 64 > CPUs, or on 32-bit systems, more than 32 CPUs). The patches are as > follows: > > 1. Add WARN_ON_ONCE() consistency checks to catch bugs. These > are all on slowpaths, so are appropriate for production use. > > 2. Apply the results of a code walkthrough of rcutree_plugin.h. > This includes a fix for a theoretical race that could result in > excessively long RCU grace periods, or perhaps even hangs/OOMs. > > 3. Fix a bug introduced in a bugfix commit #de078d875 that caused > large systems to only partially initialize the fields in the > rcu_node tree. TREE_RCU doesn't care about any of these fields, > which explains why only TREE_PREEMPT_RCU was broken. > > With these fixes, large systems using TREE_PREEMPT_RCU pass moderate > rcutorture runs (but with Josh Triplett's mods that force frequent > preemption within RCU read-side critical sections). I am sure that > there are more bugs, but these fixes get things much closer. > > b/kernel/rcutree.c | 13 +++++++++---- > b/kernel/rcutree_plugin.h | 21 ++++++++++++++------- > kernel/rcutree.c | 38 +++++++++----------------------------- > kernel/rcutree_plugin.h | 16 +++++++++------- > 4 files changed, 41 insertions(+), 47 deletions(-) Thanks Paul, applied them to tip:core/urgent. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/