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Subject: Re: [PATCH RFC net-next 2/2] drivers: net: virtio_net: Add tx_timeout
 function
To:     "Michael S. Tsirkin" <mst@redhat.com>, jcfaracco@gmail.com
Cc:     netdev@vger.kernel.org, davem@davemloft.net,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, dnmendes76@gmail.com
References: <20191006184515.23048-1-jcfaracco@gmail.com>
 <20191006184515.23048-3-jcfaracco@gmail.com>
 <20191007034402-mutt-send-email-mst@kernel.org>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <e9a88540-6f5c-23e5-b8d2-a3836ec71858@redhat.com>
Date:   Sat, 12 Oct 2019 20:59:48 +0800
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On 2019/10/7 下午3:51, Michael S. Tsirkin wrote:
> On Sun, Oct 06, 2019 at 03:45:15PM -0300, jcfaracco@gmail.com wrote:
>> From: Julio Faracco <jcfaracco@gmail.com>
>>
>> To enable dev_watchdog, virtio_net should have a tx_timeout defined
>> (.ndo_tx_timeout). This is only a skeleton to throw a warn message. It
>> notifies the event in some specific queue of device. This function
>> still counts tx_timeout statistic and consider this event as an error
>> (one error per queue), reporting it.
>>
>> Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
>> Signed-off-by: Daiane Mendes <dnmendes76@gmail.com>
>> Cc: Jason Wang <jasowang@redhat.com>
>> ---
>>   drivers/net/virtio_net.c | 27 +++++++++++++++++++++++++++
>>   1 file changed, 27 insertions(+)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 27f9b212c9f5..4b703b4b9441 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -2585,6 +2585,29 @@ static int virtnet_set_features(struct net_device *dev,
>>   	return 0;
>>   }
>>   
>> +static void virtnet_tx_timeout(struct net_device *dev)
>> +{
>> +	struct virtnet_info *vi = netdev_priv(dev);
>> +	u32 i;
>> +
>> +	/* find the stopped queue the same way dev_watchdog() does */
> not really - the watchdog actually looks at trans_start.
>
>> +	for (i = 0; i < vi->curr_queue_pairs; i++) {
>> +		struct send_queue *sq = &vi->sq[i];
>> +
>> +		if (!netif_xmit_stopped(netdev_get_tx_queue(dev, i)))
>> +			continue;
>> +
>> +		u64_stats_update_begin(&sq->stats.syncp);
>> +		sq->stats.tx_timeouts++;
>> +		u64_stats_update_end(&sq->stats.syncp);
>> +
>> +		netdev_warn(dev, "TX timeout on send queue: %d, sq: %s, vq: %d, name: %s\n",
>> +			    i, sq->name, sq->vq->index, sq->vq->name);
> this seems to assume any running queue is timed out.
> doesn't look right.
>
> also - there's already a warning in this case in the core. do we need another one?
>
>> +		dev->stats.tx_errors++;
>
>
>> +	}
>> +}
>> +
>>   static const struct net_device_ops virtnet_netdev = {
>>   	.ndo_open            = virtnet_open,
>>   	.ndo_stop   	     = virtnet_close,
>> @@ -2600,6 +2623,7 @@ static const struct net_device_ops virtnet_netdev = {
>>   	.ndo_features_check	= passthru_features_check,
>>   	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
>>   	.ndo_set_features	= virtnet_set_features,
>> +	.ndo_tx_timeout		= virtnet_tx_timeout,
>>   };
>>   
>>   static void virtnet_config_changed_work(struct work_struct *work)
>> @@ -3018,6 +3042,9 @@ static int virtnet_probe(struct virtio_device *vdev)
>>   	dev->netdev_ops = &virtnet_netdev;
>>   	dev->features = NETIF_F_HIGHDMA;
>>   
>> +	/* Set up dev_watchdog cycle. */
>> +	dev->watchdog_timeo = 5 * HZ;
>> +
> Seems to be still broken with napi_tx = false.


With napi_tx = false, we still have tx interrupt after we stop the queue 
which looks fine I believe?

Thanks


>
>>   	dev->ethtool_ops = &virtnet_ethtool_ops;
>>   	SET_NETDEV_DEV(dev, &vdev->dev);
>>   
>> -- 
>> 2.21.0