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Date:   Thu, 4 Nov 2021 06:59:35 -0400
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Subject: Re: [RFC PATCH v3 0/3] Introduce BPF map tracing capability
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To:     Joe Burton <jevburton.kernel@gmail.com>
Cc:     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>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, bpf@vger.kernel.org,
        Petar Penkov <ppenkov@google.com>,
        Stanislav Fomichev <sdf@google.com>,
        Joe Burton <jevburton@google.com>
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From:   Jamal Hadi Salim <jhs@mojatatu.com>
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On 2021-11-03 13:12, Joe Burton wrote:
> That's a good point. Since the probe is invoked before the update takes
> place, it would not be possible to account for the possibility that the
> update failed.
> 
> Unless someone wants the `pre update' hook, I'll simply adjust the
> existing hooks' semantics so that they are invoked after the update.
> As discussed, this better suits the intended use case.
>

If the goal is to synchronize state between two maps (if i understood
correctly the intent) then it is more useful to go post-update.

cheers,
jamal