Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756700AbZFZCLq (ORCPT ); Thu, 25 Jun 2009 22:11:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752724AbZFZCLh (ORCPT ); Thu, 25 Jun 2009 22:11:37 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:58949 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428AbZFZCLg (ORCPT ); Thu, 25 Jun 2009 22:11:36 -0400 Date: Thu, 25 Jun 2009 19:11:41 -0700 (PDT) Message-Id: <20090625.191141.261414015.davem@davemloft.net> To: davidel@xmailserver.org Cc: eric.dumazet@gmail.com, oleg@redhat.com, jolsa@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, fbl@redhat.com, nhorman@redhat.com, htejun@gmail.com Subject: Re: [PATCH] net: fix race in the receive/select From: David Miller In-Reply-To: References: <4A442B65.8040701@gmail.com> X-Mailer: Mew version 6.2.51 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 832 Lines: 20 From: Davide Libenzi Date: Thu, 25 Jun 2009 19:04:04 -0700 (PDT) > On Fri, 26 Jun 2009, Eric Dumazet wrote: > >> Adding a plain smp_mb() in tcp_poll() for example would slowdown select()/poll() with NULL >> timeout. > > Do you think of it as good design adding an MB on a subsystem, because of > the special locking logic of another one? > The (eventual) slowdown, IMO can be argued sideways, by saying that > non-socket users will pay the price for their polls. Perhaps every performance argument is moot since spin_unlock() used to have the barrier :-) -- 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/