From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH net-next 1/5] bonding: convert to list API and replace bond's custom list Date: Wed, 31 Jul 2013 11:56:57 -0700 Message-ID: <20130731115657.4262a7fe@nehalam.linuxnetplumber.net> References: <1375283553-32070-1-git-send-email-nikolay@redhat.com> <1375283553-32070-2-git-send-email-nikolay@redhat.com> <20130731113717.32f48d71@nehalam.linuxnetplumber.net> <51F95B21.5020004@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, andy@greyhouse.net, davem@davemloft.net, fubar@us.ibm.com To: Nikolay Aleksandrov Return-path: Received: from mail-pa0-f45.google.com ([209.85.220.45]:53777 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757132Ab3GaS5C (ORCPT ); Wed, 31 Jul 2013 14:57:02 -0400 Received: by mail-pa0-f45.google.com with SMTP id bg4so1200289pad.4 for ; Wed, 31 Jul 2013 11:57:01 -0700 (PDT) In-Reply-To: <51F95B21.5020004@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 31 Jul 2013 20:44:49 +0200 Nikolay Aleksandrov wrote: > On 07/31/2013 08:37 PM, Stephen Hemminger wrote: > > On Wed, 31 Jul 2013 17:12:29 +0200 > > Nikolay Aleksandrov wrote: > > > >> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c > >> index 390061d..80e288c 100644 > >> --- a/drivers/net/bonding/bond_3ad.c > >> +++ b/drivers/net/bonding/bond_3ad.c > >> @@ -143,10 +143,13 @@ static inline struct bonding *__get_bond_by_port(struct port *port) > >> */ > >> static inline struct port *__get_first_port(struct bonding *bond) > >> { > >> + struct slave *first_slave; > >> + > >> if (bond->slave_cnt == 0) > >> return NULL; > >> + first_slave = bond_first_slave(bond); > > > > As Jay said, it would be be better to have bond_first_slave return > > NULL (if no slaves), and eliminate slave_cnt. It would also fix > > a race here between slave_cnt and all slave's being removed. > > > Hi Stephen, > First off - thank you for the review. > > What do you mean by eliminate slave_cnt ? > We need it for various calculations throughout the bonding. > There's no race here because read_lock(&bond->lock) is held every time this > is called and slave_cnt can change only under write_lock of the same lock, > the 3ad code is not yet converted to RCU. > > Nik I would hope the goal would be to eliminate all read_lock's and allow it to be totally RCU based. You could then reduce slave_cnt to being only accessed by under a spin_lock when doing management actions.