From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753878AbZJGEsa (ORCPT ); Wed, 7 Oct 2009 00:48:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751355AbZJGEs3 (ORCPT ); Wed, 7 Oct 2009 00:48:29 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:51067 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753172AbZJGEs2 (ORCPT ); Wed, 7 Oct 2009 00:48:28 -0400 Date: Tue, 6 Oct 2009 21:47:48 -0700 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, 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, dhowells@redhat.com Subject: [PATCH tip/core/rcu 0/3] rcu: prevent hangs by simplifying rcu_barrier/CPU-hotplug, fix lockdep complaint Message-ID: <20091007044748.GA12763@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patchset fixes a couple of issues with TREE_PREEMPT_RCU: 1. The current implementation of rcu_barrier() waits for any prior CPU-hotplug operation to complete. This code path has resulted in some hangs, so first move this code from rcupdate.c to rcutree.c and then use a simpler algorithm that avoids the waiting, eliminating the possibility of such hangs. 2. The lockdep facility complains from time to time due to the fact that certain combinations of CPU-hotplug operations can cause the TREE_PREEMPT_RCU code to acquire the root rcu_node structure's lock while holding a leaf rcu_node structure's lock. This patch places the root rcu_node structure's lock into its own lockdep class to prevent this false positive. Ingo, please rewind tip/core/rcu to commit #135c8aea before applying this series, as these patches really need to go into 2.6.32. Reworked and retested rcutiny (for 2.6.33, as Linus requested) will follow in a few days. Or more patches for more bug fixes, as the case may be. ;-) b/kernel/rcupdate.c | 120 ----------------------------------- b/kernel/rcutree.c | 120 +++++++++++++++++++++++++++++++++++ b/kernel/rcutree.h | 11 ++- b/kernel/rcutree_plugin.h | 34 ++++++++++ b/kernel/rcutree_trace.c | 5 - kernel/rcutree.c | 156 ++++++++++++++++++++++++---------------------- 6 files changed, 248 insertions(+), 198 deletions(-)