Re: [dpdk-dev] [PATCH v7 1/2] ring: add reset API to flush the ring when not in use

[Olivier Matz <olivier.matz@6wind.com>]

Hi,

On Fri, Mar 15, 2019 at 11:31:25AM +0800, Gavin Hu wrote:
> Currently, the flush is done by dequeuing the ring in a while loop. It is
> much simpler to flush the queue by resetting the head and tail indices.
> 
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> ---
>  lib/librte_ring/rte_ring.h           | 20 ++++++++++++++++++++
>  lib/librte_ring/rte_ring_version.map |  7 +++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
> index af5444a..2830300 100644
> --- a/lib/librte_ring/rte_ring.h
> +++ b/lib/librte_ring/rte_ring.h
> @@ -671,6 +671,26 @@ rte_ring_dequeue(struct rte_ring *r, void **obj_p)
>  }
>  
>  /**
> + * Flush a ring.
> + *
> + * This function flush all the elements in a ring
> + *
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * @warning
> + * Make sure the ring is not in use while calling this function.
> + *
> + * @param r
> + *   A pointer to the ring structure.
> + */
> +static inline void __rte_experimental
> +rte_ring_reset(struct rte_ring *r)
> +{
> +	r->prod.head = r->cons.head = 0;
> +	r->prod.tail = r->cons.tail = 0;
> +}
> +
> +/**
>   * Return the number of entries in a ring.
>   *
>   * @param r
> diff --git a/lib/librte_ring/rte_ring_version.map b/lib/librte_ring/rte_ring_version.map
> index d935efd..581d9ca 100644
> --- a/lib/librte_ring/rte_ring_version.map
> +++ b/lib/librte_ring/rte_ring_version.map
> @@ -17,3 +17,10 @@ DPDK_2.2 {
>  	rte_ring_free;
>  
>  } DPDK_2.0;
> +
> +EXPERIMENTAL {
> +    global:
> +
> +	rte_ring_reset;
> +
> +};
> -- 
> 2.7.4
> 

To me, a static inline function does not need to be added in
rte_ring_version.map (or is it due to a check script checking the
__rte_experimental tag ?). I found at least one commit where it
is not the case:
c277b34c1b3b ("mbuf: add function returning buffer address")

There are 2 options:
1- remove the rte_ring_version.map part of the patch.
2- change the static inline function into a standard function.

I would prefer 2-, because it allows to keep an api/abi compat
layer in the future.

Regards
Olivier