From: ake <ake@igel.co.jp>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] virtio_net: avoid using netif_tx_disable() for serializing tx routine
Date: Thu, 18 Oct 2018 12:25:14 +0900 [thread overview]
Message-ID: <abd5887e-e332-190c-0a4c-d729320cae76@igel.co.jp> (raw)
In-Reply-To: <20181017110741-mutt-send-email-mst@kernel.org>
On 2018/10/18 0:09, Michael S. Tsirkin wrote:
> On Wed, Oct 17, 2018 at 07:44:12PM +0900, 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>
>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>
> Thanks a lot for debugging!
> Seems like stable material to me, right?
Yes. With this patch, we can avoid network connectivity lost
because of tx not get re-enabled under some situation. Plus, it avoids
redundant operation between netif_device_detach() and
netif_tx_disable().
I tested the patch on Linux net-next and QEMU master by suspending/
resuming the virtual machine repeatedly. The network looks no problem
and has no connectivity lost so far. I tested with both user-mode
networking and tap interface.
Best Regards
>> ---
>> 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;
>> }
>>
>> --
>> 2.19.1
next prev parent reply other threads:[~2018-10-18 3:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-11 7:51 [PATCH] virtio_net: enable tx after resuming from suspend Ake Koomsin
2018-10-11 9:44 ` Jason Wang
2018-10-11 10:22 ` ake
2018-10-11 13:06 ` Jason Wang
2018-10-12 4:30 ` ake
2018-10-12 8:23 ` Jason Wang
2018-10-12 9:18 ` ake
2018-10-15 10:08 ` ake
2018-10-16 8:53 ` Jason Wang
2018-10-16 10:15 ` ake
2018-10-17 6:18 ` Jason Wang
2018-10-17 7:59 ` [PATCH v2] virtio_net: avoid using netif_tx_disable() for serializing tx routine Ake Koomsin
2018-10-17 9:02 ` Jason Wang
2018-10-17 10:44 ` [PATCH v3] " Ake Koomsin
2018-10-17 12:30 ` Jason Wang
2018-10-17 15:09 ` Michael S. Tsirkin
2018-10-18 3:25 ` ake [this message]
2018-10-18 5:30 ` David Miller
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