linux-kernel - Re: [PATCH bpf-next v2] libbpf: Expose libbpf ringbufer epoll

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Date:   Tue, 15 Dec 2020 10:35:18 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Brendan Jackman <jackmanb@...gle.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        KP Singh <kpsingh@...omium.org>,
        Florent Revest <revest@...omium.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2] libbpf: Expose libbpf ringbufer epoll_fd

On Tue, Dec 15, 2020 at 4:18 AM Brendan Jackman <jackmanb@...gle.com> wrote:
>
> This provides a convenient perf ringbuf -> libbpf ringbuf migration
> path for users of external polling systems. It is analogous to
> perf_buffer__epoll_fd.
>
> Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
> ---
> Difference from v1: Added entry to libbpf.map.
>

I've already applied this yesterday as a4d2a7ad8683 ("libbpf: Expose
libbpf ring_buffer epoll_fd"), no need to re-send.

>  tools/lib/bpf/libbpf.h   | 1 +
>  tools/lib/bpf/libbpf.map | 1 +
>  tools/lib/bpf/ringbuf.c  | 6 ++++++
>  3 files changed, 8 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 6909ee81113a..cde07f64771e 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -536,6 +536,7 @@ LIBBPF_API int ring_buffer__add(struct ring_buffer *rb, int map_fd,
>                                 ring_buffer_sample_fn sample_cb, void *ctx);
>  LIBBPF_API int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms);
>  LIBBPF_API int ring_buffer__consume(struct ring_buffer *rb);
> +LIBBPF_API int ring_buffer__epoll_fd(struct ring_buffer *rb);
>
>  /* Perf buffer APIs */
>  struct perf_buffer;
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 7c4126542e2b..7be850271be6 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -348,4 +348,5 @@ LIBBPF_0.3.0 {
>                 btf__new_split;
>                 xsk_setup_xdp_prog;
>                 xsk_socket__update_xskmap;
> +                ring_buffer__epoll_fd;

I've put this in the alphabetic order...

>  } LIBBPF_0.2.0;
> diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
> index 5c6522c89af1..45a36648b403 100644
> --- a/tools/lib/bpf/ringbuf.c
> +++ b/tools/lib/bpf/ringbuf.c
> @@ -282,3 +282,9 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
>         }
>         return cnt < 0 ? -errno : res;
>  }
> +
> +/* Get an fd that can be used to sleep until data is available in the ring(s) */
> +int ring_buffer__epoll_fd(struct ring_buffer *rb)

... and also added const here, btw.

> +{
> +       return rb->epoll_fd;
> +}
>
> base-commit: b4fe9fec51ef48011f11c2da4099f0b530449c92
> --
> 2.29.2.576.ga3fc446d84-goog
>