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

[Wiles, Keith]

> On Jan 30, 2017, at 8:38 AM, Pascal Mazon <pascal.mazon at 6wind.com> wrote:
> 
> On 01/30/2017 12:00 PM, Ferruh Yigit 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.
>> 
>> 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.
>> 
>>> 
>>> Signed-off-by: Keith Wiles <keith.wiles at intel.com>
>> 
>> <...>
>> 
> 
> Hi,
> 
> The tap PMD recently broke for me because of this patch [1].
> 
> During init (eth_dev_tap_create()), the tap PMD allocates a shared RX/TX queue through tun_alloc().
> The recent patch now releases existing queues in rx_queue_setup(), before adding new ones.
> 
> When rx_queue_setup() is called, it uses close() calls on all shared queues, effectively deleting the netdevice.
> That's the main issue here.
> 
> I tested Keith's patch [2], and it fixes that issue, using separate queues.
> 
> There is however a couple of other queues-related issues in the tap PMD, but I'm not sure how to address them properly:
> 
> 1. internals->fds[] gets filled only with RX queues (appart from index 0 that is common to both RX and TX).
>   It means that RX queues only will be deleted when calling rte_pmd_tap_remove() or tap_tx_queue_release().
> 
> 2. tap_dev_stop() is not symmetrical with tap_dev_start(): queues won't get re-created after a stop.
> 
> It may be best to keep the very first fd (created with tun_alloc() in eth_dev_tap_create() during probe) apart.
> And then add separate TX/RX queues in internals->txq[] and internals->rxq[] respectively.
> What do you think?
> 
> [1] d00d7cc88335 ("ethdev: release queue before setting up")
> [2] http://dpdk.org/ml/archives/dev/2017-January/056470.html

Lets keep the current patch just to get over the current problem if everyone agrees. I will address the comments Pascal brings up as a later updated to the TAP PMD or I can try to get the other issues cleaned up.

> 
> 
> -- 
> Pascal Mazon
> www.6wind.com

Regards,
Keith