From patchwork Tue Mar 6 09:57:34 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lai Jiangshan X-Patchwork-Id: 7105 Return-Path: X-Original-To: patchwork@peony.canonical.com Delivered-To: patchwork@peony.canonical.com Received: from fiordland.canonical.com (fiordland.canonical.com [91.189.94.145]) by peony.canonical.com (Postfix) with ESMTP id B15C023E64 for ; Tue, 6 Mar 2012 09:53:15 +0000 (UTC) Received: from mail-iy0-f180.google.com (mail-iy0-f180.google.com [209.85.210.180]) by fiordland.canonical.com (Postfix) with ESMTP id 7B6B3A182F7 for ; Tue, 6 Mar 2012 09:53:15 +0000 (UTC) Received: by mail-iy0-f180.google.com with SMTP id e36so9163325iag.11 for ; Tue, 06 Mar 2012 01:53:15 -0800 (PST) Received: from mr.google.com ([10.50.45.228]) by 10.50.45.228 with SMTP id q4mr8375998igm.58.1331027595341 (num_hops = 1); Tue, 06 Mar 2012 01:53:15 -0800 (PST) MIME-Version: 1.0 Received: by 10.50.45.228 with SMTP id q4mr6931069igm.58.1331027595276; Tue, 06 Mar 2012 01:53:15 -0800 (PST) X-Forwarded-To: linaro-patchwork@canonical.com X-Forwarded-For: patch@linaro.org linaro-patchwork@canonical.com Delivered-To: patches@linaro.org Received: by 10.231.53.18 with SMTP id k18csp52105ibg; Tue, 6 Mar 2012 01:53:14 -0800 (PST) Received: by 10.68.136.71 with SMTP id py7mr51375998pbb.76.1331027594645; Tue, 06 Mar 2012 01:53:14 -0800 (PST) Received: from song.cn.fujitsu.com ([222.73.24.84]) by mx.google.com with ESMTP id l7si24145400pbd.320.2012.03.06.01.53.13; Tue, 06 Mar 2012 01:53:14 -0800 (PST) Received-SPF: neutral (google.com: 222.73.24.84 is neither permitted nor denied by best guess record for domain of laijs@cn.fujitsu.com) client-ip=222.73.24.84; Authentication-Results: mx.google.com; spf=neutral (google.com: 222.73.24.84 is neither permitted nor denied by best guess record for domain of laijs@cn.fujitsu.com) smtp.mail=laijs@cn.fujitsu.com X-IronPort-AV: E=Sophos;i="4.73,539,1325433600"; d="scan'208";a="4464391" Received: from unknown (HELO tang.cn.fujitsu.com) ([10.167.250.3]) by song.cn.fujitsu.com with ESMTP; 06 Mar 2012 17:53:09 +0800 Received: from mailserver.fnst.cn.fujitsu.com (tang.cn.fujitsu.com [127.0.0.1]) by tang.cn.fujitsu.com (8.14.3/8.13.1) with ESMTP id q269rAgM019492; Tue, 6 Mar 2012 17:53:10 +0800 Received: from localhost.localdomain ([10.167.225.146]) by mailserver.fnst.cn.fujitsu.com (Lotus Domino Release 8.5.1FP4) with ESMTP id 2012030617511643-893318 ; Tue, 6 Mar 2012 17:51:16 +0800 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 X-Gm-Message-State: ALoCoQlMuxH+vAilRCHOkSWadkY4GPUP7PnH7n40JoE51peT8Y47oCw17LBjJGBvKvWI7/8zfRZq 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; } /**