[dpdk-dev] eventdev: method for finding out unlink status

[Elo, Matias (Nokia - FI/Espoo)]

>>>>>>> 
>>>>>>> I think the end result we're hoping for is something like pseudo code below,
>>>>>>> (keep in mind that the event/sw has a service-core thread running it, so no
>>>>>>> application code there):
>>>>>>> 
>>>>>>> int worker_poll = 1;
>>>>>>> 
>>>>>>> worker() {
>>>>>>> while(worker_poll) {
>>>>>>>  // eventdev_dequeue_burst() etc
>>>>>>> }
>>>>>>> go_to_sleep(1);
>>>>>>> }
>>>>>>> 
>>>>>>> control_plane_scale_down() {
>>>>>>> unlink(evdev, worker, queue_id);
>>>>>>> while(unlinks_in_progress(evdev) > 0)
>>>>>>>   usleep(100);
>>>>>>> 
>>>>>>> /* here we know that the unlink is complete.
>>>>>>> * so we can now stop the worker from polling */
>>>>>>> worker_poll = 0;
>>>>>>> }
>>>>>> 
>>>>>> 
>>>>>> Make sense. Instead of rte_event_is_unlink_in_progress(), How about
>>>>>> adding a callback in rte_event_port_unlink() which will be called on
>>>>>> unlink completion. It will reduce the need for ONE more API.
>>>>>> 
>>>>>> Anyway it RC2 now, so we can not accept a new feature. So we will have
>>>>>> time for deprecation notice.
>>>>>> 
>>>>> 
>>>>> Both solutions should work but I would perhaps favor Harry's approach as it
>>>>> requires less code in the application side and doesn't break backward
>>>>> compatibility.
>>>> 
>>>> OK.
>>>> 
>>>> Does rte_event_port_unlink() returning -EBUSY will help?
>>> 
>>> It could perhaps work. The return value becomes a bit ambiguous though. E.g. how
>>> to differentiate a delayed unlink completion from a scenario where the port & queues
>>> have never been linked?
>> 
>> Based on return code?
> 
> Yes, that works. I was thinking about the complexity of the implementation as it would
> have to also track the pending unlink requests. But anyway, Harry is better answering
> these questions since I guess he would be implementing this.


Hi Harry,

Have you had time to think about this?