Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755042Ab2BAHRT (ORCPT ); Wed, 1 Feb 2012 02:17:19 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:55625 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752859Ab2BAHRR (ORCPT ); Wed, 1 Feb 2012 02:17:17 -0500 Message-ID: <4F28E7A0.6000309@cn.fujitsu.com> Date: Wed, 01 Feb 2012 15:20:00 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: Eric Dumazet CC: David Miller , netdev , LKML , Cgroups , Neil Horman , Herbert Xu Subject: Re: [PATCH 6/6] cls_cgroup: remove redundant rcu_read_lock/unlock References: <4F28E1D1.900@cn.fujitsu.com> <4F28E22A.703@cn.fujitsu.com> <1328080039.22641.2.camel@edumazet-laptop> In-Reply-To: <1328080039.22641.2.camel@edumazet-laptop> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2012-02-01 15:15:54, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2012-02-01 15:15:55, Serialize complete at 2012-02-01 15:15:55 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1011 Lines: 34 Cc: Herbert Xu >> diff --git a/net/core/sock.c b/net/core/sock.c >> index 213c856..c0bab23 100644 >> --- a/net/core/sock.c >> +++ b/net/core/sock.c >> @@ -1160,9 +1160,7 @@ void sock_update_classid(struct sock *sk) >> { >> u32 classid; >> >> - rcu_read_lock(); /* doing current task, which cannot vanish. */ >> classid = task_cls_classid(current); >> - rcu_read_unlock(); >> if (classid && classid != sk->sk_classid) >> sk->sk_classid = classid; > > Yes, this seems fine. > > Then, I wonder why we do the "if (classid && classid != sk->sk_classid)" > > before the : > > sk->sk_classid = classid; > > This seems unnecessary checks. > I was wondering about this too. He who added this may provide us with an answer. -- 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/