Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751378AbaDUGbp (ORCPT ); Mon, 21 Apr 2014 02:31:45 -0400 Received: from g2t1383g.austin.hp.com ([15.217.136.92]:11220 "EHLO g2t1383g.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751076AbaDUGbn (ORCPT ); Mon, 21 Apr 2014 02:31:43 -0400 Message-ID: <5354BAEE.9000005@hp.com> Date: Mon, 21 Apr 2014 14:30:06 +0800 From: "Li, ZhenHua" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Sergei Shtylyov CC: "David S. Miller" , Eric Dumazet , Veaceslav Falico , Nicolas Dichtel , Jiri Pirko , stephen hemminger , Jerry Chu , Sathya Perla , Subbu Seetharaman , Ajit Khaparde , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] net: Add rtnl_lock for netif_device_attach/detach References: <1397632082-18453-1-git-send-email-zhen-hual@hp.com> <5351767E.6000404@cogentembedded.com> In-Reply-To: <5351767E.6000404@cogentembedded.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The comment is trying to explain why add a lock here. On 04/19/2014 03:01 AM, Sergei Shtylyov wrote: > Hello. > > On 04/16/2014 11:08 AM, Li, Zhen-Hua wrote: > >> From: "Li, Zhen-Hua" > >> As netif_running is called in netif_device_attach/detach. There >> should be >> rtnl_lock/unlock called, to avoid dev stat change during >> netif_device_attach >> and detach being called. >> I checked NIC some drivers, some of them have >> netif_device_attach/detach >> called between rtnl_lock/unlock, while some drivers do not. > >> This patch is tring to find a generic way to fix this for all NIC >> drivers. > >> Signed-off-by: Li, Zhen-Hua >> --- >> net/core/dev.c | 18 ++++++++++++++++++ >> 1 file changed, 18 insertions(+) > >> diff --git a/net/core/dev.c b/net/core/dev.c >> index 5b3042e..795bbc5 100644 >> --- a/net/core/dev.c >> +++ b/net/core/dev.c >> @@ -2190,10 +2190,19 @@ EXPORT_SYMBOL(__dev_kfree_skb_any); >> */ >> void netif_device_detach(struct net_device *dev) >> { >> + /** > > Hm, why kernel-doc style comment here? > >> + * As netif_running is called , rtnl_lock and unlock are needed to >> + * avoid __LINK_STATE_START bit changes during this function call. >> + */ >> + int need_unlock; >> + >> + need_unlock = rtnl_trylock(); >> if (test_and_clear_bit(__LINK_STATE_PRESENT, &dev->state) && >> netif_running(dev)) { >> netif_tx_stop_all_queues(dev); >> } >> + if (need_unlock) >> + rtnl_unlock(); >> } >> EXPORT_SYMBOL(netif_device_detach); >> >> @@ -2205,11 +2214,20 @@ EXPORT_SYMBOL(netif_device_detach); >> */ >> void netif_device_attach(struct net_device *dev) >> { >> + /** > > ... and here? > >> + * As netif_running is called , rtnl_lock and unlock are needed to >> + * avoid __LINK_STATE_START bit changes during this function call. >> + */ > > WBR, Sergei > -- 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/