[dpdk-dev] [PATCH] net/tap: driver closing tx interface on queue setup

[Ferruh Yigit]

On 1/30/2017 2:34 PM, Wiles, Keith wrote:
> 
>> On Jan 30, 2017, at 5:00 AM, Yigit, Ferruh <ferruh.yigit at intel.com> wrote:
>>
>> On 1/29/2017 2:12 AM, Keith Wiles wrote:
>>> The tap driver setup both rx and tx file descriptors when the
>>> rte_eth_rx_queue_setup() causing the tx to be closed when tx setup
>>> was called.
>>
>> Can you please describe the problem more.
>> Without this patch rx->fd == tx->fd, with this patch rx and tx has
>> different file descriptors.
> 
> Let me look at this more, I am getting the same FD for both. Must be something else going on.

After patch, tun_alloc() called twice, one for Rx_q and other for Tx_q.
And tun_alloc does open() to "/dev/net/tun", I expect they get different
file descriptors.

And if they have same FD, won't this cause same problem,
rx_queue_setup() will close the FD, if Tx_q has same FD it will have
invalid descriptor.

> 
>>
>> What was the wrong with rx and tx having same fd?
>>
>> As far as I can see, rte_eth_rx_queue_setup() won't close tx->fd, that
>> function will do nothing if rx or tx has valid fd.
> 
> The rte_eth_rx_queue_setup() look at line 1146 if rxq has a value then release it, which happens on both Rx/Tx code
> 
> 	rxq = dev->data->rx_queues;
> 	if (rxq[rx_queue_id]) {
> 		RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->rx_queue_release,
> 					-ENOTSUP);
> 		(*dev->dev_ops->rx_queue_release)(rxq[rx_queue_id]);
> 		rxq[rx_queue_id] = NULL;
> 	}

Got it thanks, I missed (relatively new) above code piece.

> 
> 	if (rx_conf == NULL)
> 		rx_conf = &dev_info.default_rxconf;
> 
> 	ret = (*dev->dev_ops->rx_queue_setup)(dev, rx_queue_id, nb_rx_desc,
> 					      socket_id, rx_conf, mp);
> 
>>
>>>
>>> Signed-off-by: Keith Wiles <keith.wiles at intel.com>
>>
>> <...>
> 
> Regards,
> Keith
>