Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v3] virtio_net: avoid using netif_tx_disable() for
 serializing tx routine
To:     Ake Koomsin <ake@igel.co.jp>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <276ac5bb-90f7-5fb6-a826-0bb05ecfa069@redhat.com>
 <20181017104419.13003-1-ake@igel.co.jp>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <9e3b3279-44b2-63a0-326c-90840c1c210d@redhat.com>
Date:   Wed, 17 Oct 2018 20:30:09 +0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <20181017104419.13003-1-ake@igel.co.jp>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2018/10/17 下午6:44, Ake Koomsin wrote:
> Commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
> introduces netif_tx_disable() after netif_device_detach() in order to
> avoid use-after-free of tx queues. However, there are two issues.
>
> 1) Its operation is redundant with netif_device_detach() in case the
>     interface is running.
> 2) In case of the interface is not running before suspending and
>     resuming, the tx does not get resumed by netif_device_attach().
>     This results in losing network connectivity.
>
> It is better to use netif_tx_lock_bh()/netif_tx_unlock_bh() instead for
> serializing tx routine during reset. This also preserves the symmetry
> of netif_device_detach() and netif_device_attach().
>
> Fixes commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
> Signed-off-by: Ake Koomsin <ake@igel.co.jp>
> ---
>   drivers/net/virtio_net.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 3f5aa59c37b7..3e2c041d76ac 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2267,8 +2267,9 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
>   	/* Make sure no work handler is accessing the device */
>   	flush_work(&vi->config_work);
>   
> +	netif_tx_lock_bh(vi->dev);
>   	netif_device_detach(vi->dev);
> -	netif_tx_disable(vi->dev);
> +	netif_tx_unlock_bh(vi->dev);
>   	cancel_delayed_work_sync(&vi->refill);
>   
>   	if (netif_running(vi->dev)) {
> @@ -2304,7 +2305,9 @@ static int virtnet_restore_up(struct virtio_device *vdev)
>   		}
>   	}
>   
> +	netif_tx_lock_bh(vi->dev);
>   	netif_device_attach(vi->dev);
> +	netif_tx_unlock_bh(vi->dev);
>   	return err;
>   }
>   


Acked-by: Jason Wang <jasowang@redhat.com>

Thanks