[dpdk-dev] [PATCH v2] ethdev: add new RX/TX queue state arrays in rte_eth_dev_data

[Ananyev, Konstantin]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Qiu, Michael
> Sent: Wednesday, September 23, 2015 7:57 AM
> To: Stephen Hemminger; De Lara Guarch, Pablo
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2] ethdev: add new RX/TX queue state arrays in rte_eth_dev_data
> 
> On 2015/9/22 6:40, Stephen Hemminger wrote:
> > On Wed, 16 Sep 2015 22:51:24 +0100
> > Pablo de Lara <pablo.de.lara.guarch at intel.com> wrote:
> >
> >> This is important to avoid trying to start/stop twice a queue,
> >> which will result in undefined behaviour
> >> (which may cause RX/TX disruption).
> >>
> >> Mind that only the PMDs which have queue_start/stop functions
> >> have been changed to update this field, as the functions will
> >> check the queue state before switching it.
> >>
> >> Signed-off-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
> > I agree that the DPDK API should check for buggy manipulation
> > in the control path. But this should be done in generic code.
> > Anything where you have to change any driver is making more work
> > than necessary.
> 
> I agree with you, but I have a question, why we need expose the queue
> start and stop function to app?
> 
> In my opinion, user app will hardly to start a device but stop the
> device queue. what's the purpose of it?
> 

There are use cases when application need to start/stop individual queues.
DPDK vhost app would be one of the examples.   

Konstantin

> Thanks,
> Michael