[PATCH v2 2/9] bpf: document ethdev callback threading limitations

[Konstantin Ananyev]

> Document the data plane limitation in the file docstring of
> rte_bpf_ethdev.h: packet callback execution expects only one
> thread per port/queue pair at a time, making concurrent bursts
> (such as with RTE_ETH_TX_OFFLOAD_MT_LOCKFREE, shared RX queues,
> or multi-threaded software PMDs) unsupported.
Not sure what do you mean by:
'shared RX queues' and 'multi-threaded software PMDs'. Can you probably 
clarify?
>
> Rephrase the existing control plane multi-threading limitation
> to explicitly distinguish it from the data plane requirement.
>
> Signed-off-by: Marat Khalili <qm2k21 at gmail.com>
> ---
>   lib/bpf/rte_bpf_ethdev.h | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/lib/bpf/rte_bpf_ethdev.h b/lib/bpf/rte_bpf_ethdev.h
> index 686fda8d94..cf3b4048f0 100644
> --- a/lib/bpf/rte_bpf_ethdev.h
> +++ b/lib/bpf/rte_bpf_ethdev.h
> @@ -10,8 +10,12 @@
>    *
>    * API to install BPF filter as RX/TX callbacks for eth devices.
>    * Note that right now:
> - * - it is not MT safe, i.e. it is not allowed to do load/unload for the
> - *   same port/queue from different threads in parallel.
> + * - in the data plane, it expects only one thread per port/queue pair at a time.
> + *   Calling RX/TX burst functions concurrently on the same queue (e.g. when using
> + *   RTE_ETH_TX_OFFLOAD_MT_LOCKFREE, shared RX queues, or multi-threaded
> + *   software PMDs) is not supported.
> + * - in the control plane, it is not MT safe, i.e. it is not allowed to do
> + *   load/unload for the same port/queue from different threads in parallel.
AFAIK, all CP ethdev API is not MT-safe.
Not sure there is a reason to put it here again.
If you believe it is, then probably worth to mention that it follows 
ethdev CP API convention.
>    * - though it allows load/unload at runtime
>    *   (while RX/TX is ongoing on given port/queue).
>    * - allows only one BPF program per port/queue,