From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758388Ab0I1I1H (ORCPT ); Tue, 28 Sep 2010 04:27:07 -0400 Received: from mail.windriver.com ([147.11.1.11]:56032 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348Ab0I1I1F (ORCPT ); Tue, 28 Sep 2010 04:27:05 -0400 From: Dongdong Deng To: paulmck@linux.vnet.ibm.com, dipankar@in.ibm.com Cc: linux-kernel@vger.kernel.org, dongdong.deng@windriver.com Subject: [RFC PATCH] rcu: using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value Date: Tue, 28 Sep 2010 16:32:43 +0800 Message-Id: <1285662763-16748-1-git-send-email-dongdong.deng@windriver.com> X-Mailer: git-send-email 1.6.0.4 X-OriginalArrivalTime: 28 Sep 2010 08:26:40.0645 (UTC) FILETIME=[E028CB50:01CB5EE6] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value due to the caller didn't hold the root_rcu/rnp node's lock. Signed-off-by: Dongdong Deng CC: Dipankar Sarma CC: Paul E. McKenney --- kernel/rcutree.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d5bc439..07a7063 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -532,9 +532,9 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) if (rcu_cpu_stall_panicking) return; - delta = jiffies - rsp->jiffies_stall; + delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall); rnp = rdp->mynode; - if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { + if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) { /* We haven't checked in, so go dump stack. */ print_cpu_stall(rsp); -- 1.6.0.4