From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3) Date: Fri, 17 Apr 2009 01:07:10 -0700 (PDT) Message-ID: <20090417.010710.59150850.davem@davemloft.net> References: <20090416215033.3e648a7a@nehalam> <49E810B0.9000906@cosmosbay.com> <20090417054032.GD6885@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: dada1@cosmosbay.com, shemminger@vyatta.com, kaber@trash.net, torvalds@linux-foundation.org, jeff.chua.linux@gmail.com, paulus@samba.org, mingo@elte.hu, laijs@cn.fujitsu.com, jengelh@medozas.de, r000n@r000n.net, linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, benh@kernel.crashing.org, mathieu.desnoyers@polymtl.ca To: paulmck@linux.vnet.ibm.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:40446 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753552AbZDQIHT (ORCPT ); Fri, 17 Apr 2009 04:07:19 -0400 In-Reply-To: <20090417054032.GD6885@linux.vnet.ibm.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: From: "Paul E. McKenney" Date: Thu, 16 Apr 2009 22:40:32 -0700 > I completely agree that this RCU is absolutely -not- 2.6.30 material. ;-) I don't understand why we're writing such complicated code. Oh I see why, it's because not every arch uses the generic SMP helpers yet :-) Because if they did universally, we could solve this problem so simply, by merely sending a remote softirq to every online cpu. Once those all complete we have enough of a quiesce period, every cpu must have exited any netfilter packet processing code path they were in. And we could know they complete using an atomic counter or something.