From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755623AbcBZW2n (ORCPT ); Fri, 26 Feb 2016 17:28:43 -0500 Received: from mail.kernel.org ([198.145.29.136]:51974 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423397AbcBZWU1 (ORCPT ); Fri, 26 Feb 2016 17:20:27 -0500 Message-Id: <20160226214222.882011550@goodmis.org> User-Agent: quilt/0.61-1 Date: Fri, 26 Feb 2016 16:42:11 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker , "Paul E. McKenney" , Josh Cartwright , Eric Dumazet , "David S. Miller" Subject: [PATCH RT 4/7] net: Make synchronize_rcu_expedited() conditional on !RT_FULL References: <20160226214207.654222592@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=0004-net-Make-synchronize_rcu_expedited-conditional-on-RT.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4.110-rt139-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Cartwright While the use of synchronize_rcu_expedited() might make synchronize_net() "faster", it does so at significant cost on RT systems, as expediting a grace period forcibly preempts any high-priority RT tasks (via the stop_machine() mechanism). Without this change, we can observe a latency spike up to 30us with cyclictest by rapidly unplugging/reestablishing an ethernet link. Suggested-by: Paul E. McKenney Signed-off-by: Josh Cartwright Cc: bigeasy@linutronix.de Acked-by: Eric Dumazet Acked-by: David S. Miller Cc: Paul E. McKenney Link: http://lkml.kernel.org/r/20151027123153.GG8245@jcartwri.amer.corp.natinst.com Signed-off-by: Thomas Gleixner Signed-off-by: Steven Rostedt --- net/core/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 46f960a4c83b..4dbd27b16d1f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6081,7 +6081,7 @@ EXPORT_SYMBOL(free_netdev); void synchronize_net(void) { might_sleep(); - if (rtnl_is_locked()) + if (rtnl_is_locked() && !IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) synchronize_rcu_expedited(); else synchronize_rcu(); -- 2.7.0