netdev - Re: [PATCH bpf-next] libbpf: fix bail out from 'ringbuf_process

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Date:   Thu, 25 Mar 2021 21:31:39 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Pedro Tammela <pctammela@...il.com>
Cc:     Pedro Tammela <pctammela@...atatu.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] libbpf: fix bail out from 'ringbuf_process_ring()'
 on error

On Thu, Mar 25, 2021 at 8:02 AM Pedro Tammela <pctammela@...il.com> wrote:
>
> The current code bails out with negative and positive returns.
> If the callback returns a positive return code, 'ring_buffer__consume()'
> and 'ring_buffer__poll()' will return a spurious number of records
> consumed, but mostly important will continue the processing loop.
>
> This patch makes positive returns from the callback a no-op.
>
> Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
> ---
>  tools/lib/bpf/ringbuf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

Thanks. Applied to bpf tree and added:

Fixes: bf99c936f947 ("libbpf: Add BPF ring buffer support")


> diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
> index 8caaafe7e312..e7a8d847161f 100644
> --- a/tools/lib/bpf/ringbuf.c
> +++ b/tools/lib/bpf/ringbuf.c
> @@ -227,7 +227,7 @@ static int ringbuf_process_ring(struct ring* r)
>                         if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
>                                 sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
>                                 err = r->sample_cb(r->ctx, sample, len);
> -                               if (err) {
> +                               if (err < 0) {
>                                         /* update consumer pos and bail out */
>                                         smp_store_release(r->consumer_pos,
>                                                           cons_pos);
> --
> 2.25.1
>