Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752121AbXH0Gfc (ORCPT ); Mon, 27 Aug 2007 02:35:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751026AbXH0GfW (ORCPT ); Mon, 27 Aug 2007 02:35:22 -0400 Received: from mx12.go2.pl ([193.17.41.142]:56906 "EHLO poczta.o2.pl" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750928AbXH0GfV (ORCPT ); Mon, 27 Aug 2007 02:35:21 -0400 Date: Mon, 27 Aug 2007 08:36:35 +0200 From: Jarek Poplawski To: paulmck@linux.vnet.ibm.com Cc: Adrian Bunk , Gabriel C , Andrew Morton , linux-kernel@vger.kernel.org, netdev Subject: Re: net/ipv4/fib_trie.c - compile error (Re: 2.6.23-rc3-mm1) Message-ID: <20070827063635.GB1703@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070822170302.GC8786@linux.vnet.ibm.com> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2134 Lines: 50 On 22-08-2007 19:03, Paul E. McKenney wrote: > On Wed, Aug 22, 2007 at 05:41:11PM +0200, Adrian Bunk wrote: >> On Wed, Aug 22, 2007 at 05:30:13PM +0200, Gabriel C wrote: >>> Got it with a randconfig ( http://194.231.229.228/kernel/mm/2.6.23-rc3-mm1/r/randconfig-8 ) >>> >>> ... >>> >>> net/ipv4/fib_trie.c: In function 'trie_rebalance': >>> net/ipv4/fib_trie.c:969: error: lvalue required as unary '&' operand >>> net/ipv4/fib_trie.c:971: error: lvalue required as unary '&' operand >>> net/ipv4/fib_trie.c:977: error: lvalue required as unary '&' operand >>> net/ipv4/fib_trie.c:980: error: lvalue required as unary '&' operand >>> ... >> Side effect of the git-net removal, temporarily removing >> immunize-rcu_dereference-against-crazy-compiler-writers.patch should >> work around it. > > Alternatively, the following one-line patch to net/ipv4/fib_trie.c could > be used. > > Signed-off-by: Paul E. McKenney > --- > > fib_trie.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff -urpNa -X dontdiff linux-2.6.23-rc3-mm1/net/ipv4/fib_trie.c linux-2.6.23-rc3-mm1.compile/net/ipv4/fib_trie.c > --- linux-2.6.23-rc3-mm1/net/ipv4/fib_trie.c 2007-08-22 09:20:33.000000000 -0700 > +++ linux-2.6.23-rc3-mm1.compile/net/ipv4/fib_trie.c 2007-08-22 09:47:33.000000000 -0700 > @@ -94,7 +94,7 @@ typedef unsigned int t_key; > #define T_LEAF 1 > #define NODE_TYPE_MASK 0x1UL > #define NODE_PARENT(node) \ > - ((struct tnode *)rcu_dereference(((node)->parent & ~NODE_TYPE_MASK))) > + ((struct tnode *)(rcu_dereference((node)->parent) & ~NODE_TYPE_MASK)) ... After first reading of this thread I've had an impression it's about compiler's behavior, but now it seems to me this patch is not an alternative, but a 'must be' and only proper way of calling rcu_dereference (with a variable instead of an expression)? Am I right? Regards, Jarek P. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/