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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Tue, 30 Mar 2021 23:53:55 -0700
Message-ID: <CAEf4BzZ+O3x9AksV6MGuicDQO+gObFCQQR7t6UK=RBhuSbOiZg@mail.gmail.com>
Subject: Re: [PATCH bpf-next] bpf: add 'BPF_RB_MAY_WAKEUP' flag
To:     Pedro Tammela <pctammela@gmail.com>
Cc:     Pedro Tammela <pctammela@mojatatu.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
        Joe Stringer <joe@cilium.io>,
        Quentin Monnet <quentin@isovalent.com>,
        Yang Li <yang.lee@linux.alibaba.com>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
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On Sun, Mar 28, 2021 at 9:11 AM Pedro Tammela <pctammela@gmail.com> wrote:
>
> The current way to provide a no-op flag to 'bpf_ringbuf_submit()',
> 'bpf_ringbuf_discard()' and 'bpf_ringbuf_output()' is to provide a '0'
> value.
>
> A '0' value might notify the consumer if it already caught up in processing,
> so let's provide a more descriptive notation for this value.
>
> Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
> ---

flags == 0 means "no extra modifiers of behavior". That's default
adaptive notification. If you want to adjust default behavior, only
then you specify non-zero flags. I don't think anyone will bother
typing BPF_RB_MAY_WAKEUP for this, nor I think it's really needed. The
documentation update is nice (if no flags are specified notification
will be sent if needed), but the new "pseudo-flag" seems like an
overkill to me.

>  include/uapi/linux/bpf.h                               | 8 ++++++++
>  tools/include/uapi/linux/bpf.h                         | 8 ++++++++
>  tools/testing/selftests/bpf/progs/ima.c                | 2 +-
>  tools/testing/selftests/bpf/progs/ringbuf_bench.c      | 2 +-
>  tools/testing/selftests/bpf/progs/test_ringbuf.c       | 2 +-
>  tools/testing/selftests/bpf/progs/test_ringbuf_multi.c | 2 +-
>  6 files changed, 20 insertions(+), 4 deletions(-)
>

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