Re: [PATCH v6 1/2] ethdev: add query_update sync and async function calls

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 1/20/23 19:50, Gregory Etelson wrote:
> Hello Andrew,
> 
> []
> 
>> On 1/20/23 13:46, Gregory Etelson wrote:
>>>>> and it's async version `rte_flow_async_action_handle_query_update`
>>>>> to atomically query and update flow action.
>>>>
>>>> Sorry, may be I'm missing something, but after reading previous
>>>> discussion I have a feeling that update could be queried data
>>>> dependent. However, I don't understand how it could be possible
>>>> with API below. Just my misunderstanding?
>>>>
>>>
>>> The goal of `rte_flow_action_handle_query_update()` is to execute query
>> and update actions atomically.
>>> The function guaranties that action state will not change by any event
>> before both update and query complete.
>>> If the function was called with the ` RTE_FLOW_QU_QUERY_FIRST `
>> `mode` argument, then update execution can depend
>>> on query result. That's up to query format, PMD implementation and
>> hardware capabilities.
>>> I hope that answered your question.
>>
>> Sorry, I'm still confused. Could you explain a bit more,
>> please. How update could depend on query result?
> 
> Conditional update I described requires special action properties.
> Consider an action object with a method that receives query and update as parameters.
> The method will activate update only if query result satisfies action state.
> If the action was updated, both query and update were atomic for application.
> The function returns the action state - updated or not.
> Application is aware about the action properties.
> Application applies action properties to returned state to discover if action was updated.

Is it just a theoretical possibility or do you have an example
right now?

> 
>> Caller already specified update structure...
>   
> Regards,
> Gregory