From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753189AbcBTPuv (ORCPT <rfc822;w@1wt.eu>);
	Sat, 20 Feb 2016 10:50:51 -0500
Received: from mail-lb0-f169.google.com ([209.85.217.169]:35658 "EHLO
	mail-lb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1750716AbcBTPuq (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Sat, 20 Feb 2016 10:50:46 -0500
Subject: Re: [PATCH] xen-netfront: set real_num_tx_queues to zreo avoid to
 trigger BUG_ON
To: Gonglei <arei.gonglei@huawei.com>, netdev@vger.kernel.org,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
References: <1455931646-5672-1-git-send-email-arei.gonglei@huawei.com>
Cc: peter.huangpeng@huawei.com, "David S . Miller" <davem@davemloft.net>
From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Organization: Cogent Embedded
Message-ID: <56C88B51.3010706@cogentembedded.com>
Date: Sat, 20 Feb 2016 18:50:41 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.5.0
MIME-Version: 1.0
In-Reply-To: <1455931646-5672-1-git-send-email-arei.gonglei@huawei.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 02/20/2016 04:27 AM, Gonglei wrote:

> It's possible for a race condition to exist between xennet_open() and
> talk_to_netback(). After invoking netfront_probe() then other
> threads or processes invoke xennet_open (such as NetworkManager)
> immediately may trigger BUG_ON(). Besides, we also should reset
> real_num_tx_queues in xennet_destroy_queues().
>
>      [ 3324.658057] kernel BUG at include/linux/netdevice.h:508!
>      [ 3324.658057] invalid opcode: 0000 [#1] SMP
>      [ 3324.658057] CPU: 0 PID: 662 Comm: NetworkManager Tainted: G
>      [<ffffffff810bc646>] ? raw_notifier_call_chain+0x16/0x20
>      [<ffffffff8166e1be>] __dev_open+0xce/0x150
>      [<ffffffff8166e501>] __dev_change_flags+0xa1/0x170
>      [<ffffffff8166e5f9>] dev_change_flags+0x29/0x70
>      [<ffffffff8167c49f>] do_setlink+0x39f/0xb40
>      [<ffffffff813c9ce2>] ? nla_parse+0x32/0x120
>      [<ffffffff8167d544>] rtnl_newlink+0x604/0x900
>      [<ffffffff8169f453>] ? netlink_unicast+0x193/0x1c0
>      [<ffffffff81324808>] ? security_capable+0x18/0x20
>      [<ffffffff810a4e9d>] ? ns_capable+0x2d/0x60
>      [<ffffffff8167b955>] rtnetlink_rcv_msg+0xf5/0x270
>      [<ffffffff813b32bd>] ? rhashtable_lookup_compare+0x5d/0xa0
>      [<ffffffff8167b860>] ? rtnetlink_rcv+0x40/0x40
>      [<ffffffff8169fc89>] netlink_rcv_skb+0xb9/0xe0
>      [<ffffffff8167b84c>] rtnetlink_rcv+0x2c/0x40
>      [<ffffffff8169f3ed>] netlink_unicast+0x12d/0x1c0
>      [<ffffffff8169f953>] netlink_sendmsg+0x4d3/0x630
>      [<ffffffff813280a2>] ? sock_has_perm+0x72/0x90
>      [<ffffffff8164d34f>] do_sock_sendmsg+0x9f/0xc0
>      [ 3324.703482] RIP  [<ffffffffa0065a50>] xennet_open+0x180/0x182 [xen_netfront]
>
> CC: David S. Miller <davem@davemloft.net>
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>

    Full name required for this tag.

[...]

MBR, Sergei