From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965156Ab2CFJxQ (ORCPT ); Tue, 6 Mar 2012 04:53:16 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:38725 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S965118Ab2CFJxO (ORCPT ); Tue, 6 Mar 2012 04:53:14 -0500 X-IronPort-AV: E=Sophos;i="4.73,539,1325433600"; d="scan'208";a="4464391" From: Lai Jiangshan To: "Paul E. McKenney" Cc: Lai Jiangshan , linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org Subject: [PATCH 2/6] Don't touch the snap in srcu_readers_active() Date: Tue, 6 Mar 2012 17:57:34 +0800 Message-Id: <1331027858-7648-2-git-send-email-laijs@cn.fujitsu.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1331027858-7648-1-git-send-email-laijs@cn.fujitsu.com> References: <1331023359-6987-1-git-send-email-laijs@cn.fujitsu.com> <1331027858-7648-1-git-send-email-laijs@cn.fujitsu.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2012-03-06 17:51:16, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2012-03-06 17:51:19, Serialize complete at 2012-03-06 17:51:19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org srcu_readers_active() is called without the mutex, but it touch the snap. also achieve better cache locality a little Signed-off-by: Lai Jiangshan --- kernel/srcu.c | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/kernel/srcu.c b/kernel/srcu.c index b6b9ea2..fbe2d5f 100644 --- a/kernel/srcu.c +++ b/kernel/srcu.c @@ -181,7 +181,14 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) */ static int srcu_readers_active(struct srcu_struct *sp) { - return srcu_readers_active_idx(sp, 0) + srcu_readers_active_idx(sp, 1); + int cpu; + unsigned long sum = 0; + + for_each_possible_cpu(cpu) { + sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]); + sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]); + } + return sum & SRCU_REF_MASK; } /** -- 1.7.4.4