From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH net-next v2] ipv6: remove useless spin_lock/spin_unlock Date: Tue, 02 Dec 2014 21:18:46 -0800 Message-ID: <1417583926.2902.10.camel@perches.com> References: <547E6832.4070403@cn.fujitsu.com> <547E7594.7010301@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: David Miller , netdev , Eric Dumazet To: Duan Jiong Return-path: Received: from smtprelay0142.hostedemail.com ([216.40.44.142]:54949 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751270AbaLCFSt (ORCPT ); Wed, 3 Dec 2014 00:18:49 -0500 In-Reply-To: <547E7594.7010301@cn.fujitsu.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2014-12-03 at 10:29 +0800, Duan Jiong wrote: > xchg is atomic, so there is no necessary to use spin_lock/spin_unlock > to protect it. At last, remove the redundant > opt = xchg(&inet6_sk(sk)->opt, opt); statement. > > Signed-off-by: Duan Jiong > --- > v2: remove the redundant opt = xchg(&inet6_sk(sk)->opt, opt); statement. > > net/ipv6/ipv6_sockglue.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c > index e1a9583..66980d8 100644 > --- a/net/ipv6/ipv6_sockglue.c > +++ b/net/ipv6/ipv6_sockglue.c > @@ -110,12 +110,8 @@ struct ipv6_txoptions *ipv6_update_options(struct sock *sk, > icsk->icsk_ext_hdr_len = opt->opt_flen + opt->opt_nflen; > icsk->icsk_sync_mss(sk, icsk->icsk_pmtu_cookie); > } > - opt = xchg(&inet6_sk(sk)->opt, opt); > - } else { > - spin_lock(&sk->sk_dst_lock); > - opt = xchg(&inet6_sk(sk)->opt, opt); > - spin_unlock(&sk->sk_dst_lock); > } > + opt = xchg(&inet6_sk(sk)->opt, opt); > sk_dst_reset(sk); > > return opt; The original function could now be written integrating the multiple ifs like: --- net/ipv6/ipv6_sockglue.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c index e1a9583..12c9c6b 100644 --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -102,20 +102,19 @@ static struct ipv6_txoptions *ipv6_update_options(struct sock *sk, struct ipv6_txoptions *opt) { - if (inet_sk(sk)->is_icsk) { - if (opt && - !((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) && - inet_sk(sk)->inet_daddr != LOOPBACK4_IPV6) { - struct inet_connection_sock *icsk = inet_csk(sk); - icsk->icsk_ext_hdr_len = opt->opt_flen + opt->opt_nflen; - icsk->icsk_sync_mss(sk, icsk->icsk_pmtu_cookie); - } - opt = xchg(&inet6_sk(sk)->opt, opt); - } else { - spin_lock(&sk->sk_dst_lock); - opt = xchg(&inet6_sk(sk)->opt, opt); - spin_unlock(&sk->sk_dst_lock); + struct inet_sock *inet = inet_sk(sk); + + if (inet->is_icsk && + opt && + !((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) && + inet->inet_daddr != LOOPBACK4_IPV6) { + struct inet_connection_sock *icsk = inet_csk(sk); + + icsk->icsk_ext_hdr_len = opt->opt_flen + opt->opt_nflen; + icsk->icsk_sync_mss(sk, icsk->icsk_pmtu_cookie); } + + opt = xchg(&inet6_sk(sk)->opt, opt); sk_dst_reset(sk); return opt;