From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755432AbaJ1V5g (ORCPT ); Tue, 28 Oct 2014 17:57:36 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:49997 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752436AbaJ1V5c (ORCPT ); Tue, 28 Oct 2014 17:57:32 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 02/10] rcu: Use DEFINE_PER_CPU_SHARED_ALIGNED for rcu_data Date: Tue, 28 Oct 2014 14:53:29 -0700 Message-Id: <1414533217-24910-2-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1414533217-24910-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20141028215140.GA23970@linux.vnet.ibm.com> <1414533217-24910-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14102821-0033-0000-0000-000002803DA3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" The rcu_data per-CPU variable has a number of fields that are atomically manipulated, potentially by any CPU. This situation can result in false sharing with per-CPU variables that have the misfortune of being allocated adjacent to rcu_data in memory. This commit therefore changes the DEFINE_PER_CPU() to DEFINE_PER_CPU_SHARED_ALIGNED() in order to avoid this false sharing. Reported-by: Christoph Lameter Signed-off-by: Paul E. McKenney Reviewed-by: Christoph Lameter --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index c0673c56fb1a..ab6fcfb4fe11 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -105,7 +105,7 @@ struct rcu_state sname##_state = { \ .name = RCU_STATE_NAME(sname), \ .abbr = sabbr, \ }; \ -DEFINE_PER_CPU(struct rcu_data, sname##_data) +DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data) RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); -- 1.8.1.5