From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759080Ab2JKRXT (ORCPT ); Thu, 11 Oct 2012 13:23:19 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:38638 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759004Ab2JKRXS (ORCPT ); Thu, 11 Oct 2012 13:23:18 -0400 Date: Thu, 11 Oct 2012 10:22:37 -0700 From: "Paul E. McKenney" To: mingo@elte.hu Cc: linux-kernel@vger.kernel.org, fweisbec@gmail.com, kirill@shutemov.name Subject: [GIT PULL rcu/urgent] Fixes for RCU regressions Message-ID: <20121011172237.GA32051@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/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12101117-5518-0000-0000-0000085BB408 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Ingo, This series fixes some RCU regressions in 3.7. Kirill A. Shutemov found a case where synchronize_rcu() is invoked from a CPU-hotplug notifier, which, with RCU's shiny new kthread-based grace-period implementation, results in deadlock. The first commit in this series fixes this deadlock by introducing RCU-specific synchronization, so that RCU grace periods exclude only RCU's CPU-hotplug notifiers, not the entire CPU-hotplug operation. Kirill successfully tested this commit (as have I), and it has furthermore been exposed to -next testing. The other commit in this series adds a warning to the new RCU_USER_QS and RCU_USER_QS_FORCE Kconfig options, noting that these features, though reasonably stable, are probably not ready for millions of users. This commit affects only the Kconfig help text. These changes are available in the git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/urgent Thanx, Paul ------------------> Frederic Weisbecker (1): rcu: Advise most users not to enable RCU user mode Paul E. McKenney (1): rcu: Grace-period initialization excludes only RCU notifier init/Kconfig | 12 ++++++++++++ kernel/rcutree.c | 21 ++++++++++----------- kernel/rcutree.h | 6 ++++++ 3 files changed, 28 insertions(+), 11 deletions(-)