From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH net 4/4] tcp: various missing rcu_read_lock around __sk_dst_get Date: Fri, 1 Apr 2016 02:01:50 +0200 Message-ID: <56FDBA6E.5030508@stressinduktion.org> References: <1459466982-20432-1-git-send-email-hannes@stressinduktion.org> <1459466982-20432-5-git-send-email-hannes@stressinduktion.org> <1459467595.6473.233.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org, sasha.levin@oracle.com, daniel@iogearbox.net, alexei.starovoitov@gmail.com, mkubecek@suse.cz To: Eric Dumazet Return-path: Received: from out5-smtp.messagingengine.com ([66.111.4.29]:54198 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573AbcDAABz (ORCPT ); Thu, 31 Mar 2016 20:01:55 -0400 Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by mailout.nyi.internal (Postfix) with ESMTP id 6670E20C6A for ; Thu, 31 Mar 2016 20:01:54 -0400 (EDT) In-Reply-To: <1459467595.6473.233.camel@edumazet-glaptop3.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: Hi Eric, On 01.04.2016 01:39, Eric Dumazet wrote: > On Fri, 2016-04-01 at 01:29 +0200, Hannes Frederic Sowa wrote: >> Various fixes which were discovered by this changeset. More probably >> to come... > > > Really ? > > Again, TCP stack locks the socket most of the time. > > The fact that lockdep does not understand this is not a reason to add > this overhead. I don't see how lockdep does not understand this? I think I added the appropriate helper to exactly verify if we have the socket lock with lockdep, please have a look at lockdep_sock_is_held in patch #2. Some of the patches also just reorder the rcu_read_lock, which is anyway mostly free. Bye, Hannes