On Thu, Sep 14, 2023 at 4:12 PM Martin Kelly
<martin.kelly@xxxxxxxxxxxxxxx> wrote:
>
> Add APIs to get the producer and consumer position for a given
> ringbuffer.
>
> Signed-off-by: Martin Kelly <martin.kelly@xxxxxxxxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.h | 16 ++++++++++++++++
> tools/lib/bpf/libbpf.map | 2 ++
> tools/lib/bpf/ringbuf.c | 14 ++++++++++++++
> 3 files changed, 32 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 2d6c39e20863..935162dbb3bf 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -1263,6 +1263,22 @@ LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
> LIBBPF_API struct ring *ring_buffer__ring(struct ring_buffer *rb,
> unsigned int idx);
>
> +/**
> + * @brief **ring__consumer_pos()** returns the current consumer position.
> + *
> + * @param r A ring object.
> + * @return The current consumer position.
> + */
> +LIBBPF_API unsigned long ring__consumer_pos(const struct ring *r);
> +
> +/**
> + * @brief **ring__producer_pos()** returns the current producer position.
> + *
> + * @param r A ring object.
> + * @return The current producer position.
> + */
> +LIBBPF_API unsigned long ring__producer_pos(const struct ring *r);
> +
> struct user_ring_buffer_opts {
> size_t sz; /* size of this struct, for forward/backward compatibility */
> };
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 7a7370c2bc25..1c532fe7a445 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -401,4 +401,6 @@ LIBBPF_1.3.0 {
> bpf_program__attach_tcx;
> bpf_program__attach_uprobe_multi;
> ring_buffer__ring;
> + ring__consumer_pos;
> + ring__producer_pos;
we keep this list ordered, so ring__ goes before ring_b
> } LIBBPF_1.2.0;
> diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
> index 2857df0f2d03..54c596db57a4 100644
> --- a/tools/lib/bpf/ringbuf.c
> +++ b/tools/lib/bpf/ringbuf.c
> @@ -336,6 +336,20 @@ struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx)
> return rb->rings[idx];
> }
>
> +unsigned long ring__consumer_pos(const struct ring *r)
> +{
> + /* Synchronizes with smp_store_release() in ringbuf_process_ring(). */
> + return smp_load_acquire(r->consumer_pos);
> +}
> +
> +unsigned long ring__producer_pos(const struct ring *r)
> +{
> + /* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in
> + * the kernel.
> + */
> + return smp_load_acquire(r->producer_pos);
> +}
> +
> static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
> {
> if (rb->consumer_pos) {
> --
> 2.34.1
>
