From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753719AbaA0K3U (ORCPT ); Mon, 27 Jan 2014 05:29:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:31221 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753610AbaA0K3S (ORCPT ); Mon, 27 Jan 2014 05:29:18 -0500 Message-ID: <52E634DA.3040200@redhat.com> Date: Mon, 27 Jan 2014 18:28:42 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Ben Hutchings CC: David Miller , kys@microsoft.com, haiyangz@microsoft.com, devel@linuxdriverproject.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] net: hyperv: initialize link status correctly References: <1390807854-4469-1-git-send-email-jasowang@redhat.com> <20140127.003559.2290408024387922847.davem@davemloft.net> <52E629A8.5010302@redhat.com> <1390818121.2735.130.camel@deadeye.wl.decadent.org.uk> In-Reply-To: <1390818121.2735.130.camel@deadeye.wl.decadent.org.uk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/27/2014 06:22 PM, Ben Hutchings wrote: > On Mon, 2014-01-27 at 17:40 +0800, Jason Wang wrote: >> On 01/27/2014 04:35 PM, David Miller wrote: >>> From: Jason Wang >>> Date: Mon, 27 Jan 2014 15:30:54 +0800 >>> >>>> Call netif_carrier_on() after register_device(). Otherwise it won't work since >>>> the device was still in NETREG_UNINITIALIZED state. >>>> >>>> Fixes a68f9614614749727286f675d15f1e09d13cb54a >>>> (hyperv: Fix race between probe and open calls) >>>> >>>> Cc: Haiyang Zhang >>>> Cc: K. Y. Srinivasan >>>> Reported-by: Di Nie >>>> Tested-by: Di Nie >>>> Signed-off-by: Jason Wang >>> A device up can occur at the moment you call register_netdevice(), >>> therefore that up call can see the carrier as down and fail or >>> similar. So you really cannot resolve the carrier to be on in this >>> way. >> True, we need a workqueue to synchronize them. > Whatever for? All you need to do is: > > rtnl_lock(); > register_netdevice(); > netif_carrier_on(); > rtnl_unlock(); > > It would be nice if we could make the current code work with a change in > the core, though. > > Ben. > Looks like the link status interrupt may happen during this (after netvsc_device_add() was called by rndis_filter_device_add()) without any synchronization. This may lead a wrong link status here.