From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757056Ab3LWIjX (ORCPT ); Mon, 23 Dec 2013 03:39:23 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:21137 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752421Ab3LWIjW (ORCPT ); Mon, 23 Dec 2013 03:39:22 -0500 Message-ID: <52B7F669.8080207@huawei.com> Date: Mon, 23 Dec 2013 16:38:01 +0800 From: Ding Tianhong User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Toshiaki Makita CC: Stephen Hemminger , "David S. Miller" , , Netdev , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 12/21] bridge: slight optimization of addr compare References: <52B7C5D5.2040202@huawei.com> <1387787627.1797.10.camel@localhost.localdomain> In-Reply-To: <1387787627.1797.10.camel@localhost.localdomain> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.72.199] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2013/12/23 16:33, Toshiaki Makita wrote: > On Mon, 2013-12-23 at 13:10 +0800, Ding Tianhong wrote: >> Use the recently added and possibly more efficient >> ether_addr_equal_unaligned to instead of memcmp. >> >> Cc: Stephen Hemminger >> Cc: David Miller >> Cc: bridge@lists.linux-foundation.org >> Cc: netdev@vger.kernel.org >> Signed-off-by: Wang Weidong >> Signed-off-by: Ding Tianhong >> --- >> net/bridge/br_stp_if.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c >> index 656a6f3..04217d1 100644 >> --- a/net/bridge/br_stp_if.c >> +++ b/net/bridge/br_stp_if.c >> @@ -229,7 +229,7 @@ bool br_stp_recalculate_bridge_id(struct net_bridge *br) >> >> list_for_each_entry(p, &br->port_list, list) { >> if (addr == br_mac_zero || >> - memcmp(p->dev->dev_addr, addr, ETH_ALEN) < 0) >> + !ether_addr_equal_unaligned(p->dev->dev_addr, addr) < 0) >> addr = p->dev->dev_addr; >> >> } > > We cannot do this change. > !ether_addr_equal() isn't identical to memcmp(). > memcmp() can return negative value but ether_addr_equal() cannot. > br_stp_recalculate_bridge_id() is searching the smallest address among > its ports. This change breaks it. > > Thanks, > Toshiaki Makita Yes, I miss it, the negative value is useful here, thanks for point out. Regards Ding > > >