netdev - Re: [PATCH bpf-next 2/2] libbpf, xsk: add libbpf_smp_store_release libbpf_smp_load

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Message-ID: <87k0qqx3be.fsf@toke.dk>
Date:   Mon, 01 Mar 2021 17:10:29 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Björn Töpel <bjorn.topel@...il.com>,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com, jonathan.lemon@...il.com,
        maximmi@...dia.com, andrii@...nel.org
Subject: Re: [PATCH bpf-next 2/2] libbpf, xsk: add libbpf_smp_store_release
 libbpf_smp_load_acquire

Björn Töpel <bjorn.topel@...il.com> writes:

> From: Björn Töpel <bjorn.topel@...el.com>
>
> Now that the AF_XDP rings have load-acquire/store-release semantics,
> move libbpf to that as well.
>
> The library-internal libbpf_smp_{load_acquire,store_release} are only
> valid for 32-bit words on ARM64.
>
> Also, remove the barriers that are no longer in use.

So what happens if an updated libbpf is paired with an older kernel (or
vice versa)?

-Toke