From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: Fun with if_bridge.h and br_private.h Date: Mon, 3 May 2010 13:36:13 -0700 Message-ID: <20100503133613.0f2a61f7@nehalam> References: <20100503191256.GA18110@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, arnd@arndb.de To: paulmck@linux.vnet.ibm.com Return-path: Received: from mail.vyatta.com ([76.74.103.46]:34872 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753783Ab0ECUg2 (ORCPT ); Mon, 3 May 2010 16:36:28 -0400 In-Reply-To: <20100503191256.GA18110@linux.vnet.ibm.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 3 May 2010 12:12:56 -0700 "Paul E. McKenney" wrote: > Hello, Stephen, > > I need some help with #include issues surrounding bridge. > > Arnd has been putting together a sparse-based RCU-checking tool > that can detect pointer access that should have been protected by an > rcu_dereference() or rcu_assign_pointer(). On of the side-effects of > his approach is that rcu_dereference() can no longer handle pointers > to incomplete types, as Arnd's approach uses the address-space feature > of sparse, which in turn must tag the type pointed to rather than the > pointer itself. And this in turn requires rcu_dereference() and friends > to see the pointed-to type as well as the pointer type. > > One place affected by this is handle_bridge() in net/core/dev.c, which > invokes rcu_dereference() on skb->dev->br_port, which is of type struct > net_bridge_port, which is defined in net/bridge/br_private.h. This is, > well, private, but is included into a couple places in netfilter and atm, > so I tried including it into net/core/dev.c. > > This still left me with forward references: > > In file included from net/core/dev.c:104: > include/linux/if_bridge.h:106: warning: "struct net_bridge_port" declared inside parameter list > include/linux/if_bridge.h:106: warning: its scope is only this definition or declaration, which is probably not what you want > net/core/dev.c:2331: error: conflicting types for "br_handle_frame_hook" > include/linux/if_bridge.h:105: error: previous declaration of "br_handle_frame_hook" was here > net/core/dev.c:2333: error: conflicting types for "br_handle_frame_hook" > include/linux/if_bridge.h:105: error: previous declaration of "br_handle_frame_hook" was here > > This happens because net/bridge/br_private.h includes if_bridge.h before > it defines net_bridge_port. > > Any thoughts on how best to allow handle_bridge() see the definition > of struct net_bridge_port? > Why not make it a void *, there is no reason to make core code depend on br_private.h.