From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754079Ab0EFXMV (ORCPT ); Thu, 6 May 2010 19:12:21 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:43597 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752105Ab0EFXMU (ORCPT ); Thu, 6 May 2010 19:12:20 -0400 Date: Thu, 6 May 2010 16:12:11 -0700 From: "Paul E. McKenney" To: Arnd Bergmann Cc: Stephen Hemminger , linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, David Miller Subject: Re: [PATCH tip/core/rcu 28/48] net: Make accesses to ->br_port safe for sparse RCU Message-ID: <20100506231211.GK2325@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100504201934.GA19234@linux.vnet.ibm.com> <201005042341.49480.arnd@arndb.de> <20100505220355.GA20938@linux.vnet.ibm.com> <201005061609.25960.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201005061609.25960.arnd@arndb.de> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 06, 2010 at 04:09:25PM +0200, Arnd Bergmann wrote: > On Thursday 06 May 2010, Paul E. McKenney wrote: > > On Tue, May 04, 2010 at 11:41:49PM +0200, Arnd Bergmann wrote: > > > On Tuesday 04 May 2010 23:26:31 Stephen Hemminger wrote: > > > > > The new versions of the rcu_dereference() APIs requires that any pointers > > > > > passed to one of these APIs be fully defined. The ->br_port field > > > > > in struct net_device points to a struct net_bridge_port, which is an > > > > > incomplete type. This commit therefore changes ->br_port to be a void*, > > > > > and introduces a br_port() helper function to convert the type to struct > > > > > net_bridge_port, and applies this new helper function where required. > > > > > > > > I would rather make the bridge hook generic and not take a type argument. > > > > > > Not sure if you were confused by the comment in the same way that I was. > > > > > > The bridge hook is not impacted by this at all, since we can either pass > > > a void* or a struct net_bridge_port* to it. The br_port() helper > > > is used for all the places where we actually want to dereference > > > dev->br_port and access its contents. > > > > What should I change in the commit message to clear this up? > > > > Of course, if the code needs to change, please let me know what should > > change there as well. > > I think it's both ok, I was mostly confused by the discussion we had earlier. > Maybe add a sentence like: > > The br_handle_frame_hook now needs a forward declaration of struct net_bridge_port. Done! > Or you just change br_handle_frame_hook to take a void* to avoid the forward > declaration. Not sure what Stephen was referring to really. This sounds like a way to make things quite a bit more intrusive, so holding off on this. Thanx, Paul