Re: [dpdk-dev] [PATCH v2] rte_ring: clarify preemptible nature of ring algorithm

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

I do not see the documentation regarding this in programmer's guide.

-----Original Message-----
From: Burakov, Anatoly <anatoly.burakov@intel.com>
Sent: Tuesday, May 29, 2018 4:10 AM
To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>; olivier.matz@6wind.com
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] rte_ring: clarify preemptible nature of ring algorithm

On 29-May-18 6:28 AM, Honnappa Nagarahalli wrote:
> rte_ring implementation is not preemptible only under certain
> circumstances. This clarification is helpful for data plane and
> control plane communication using rte_ring.
>
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Gavin Hu <gavin.hu@arm.com>
> Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
> ---
> v2:
> * Fixed checkpatch warnings
>
>   lib/librte_ring/rte_ring.h | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
> index d3d3f7f..2f9c945 100644
> --- a/lib/librte_ring/rte_ring.h
> +++ b/lib/librte_ring/rte_ring.h
> @@ -26,8 +26,13 @@
>    * - Bulk dequeue.
>    * - Bulk enqueue.
>    *
> - * Note: the ring implementation is not preemptable. A lcore must not
> - * be interrupted by another task that uses the same ring.
> + * Note: the ring implementation can block threads from completing
> + their
> + * operation under the following circumstances.
> + * A preempted thread can block other threads (operating on the same
> + ring)
> + * from completing their operations, only if those threads are
> + performing
> + * the same ring operation (enqueue/dequeue) as the preempted thread.
> + * In other words, a preempted consumer thread will not block any
> + producer
> + * threads and vice versa.
>    *
>    */
>
>

Similar clarification is already present in Programmer's Guide for rte_ring section. Perhaps it would be good to reference it here?

--
Thanks,
Anatoly
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