netdev - Re: [PATCH bpf-next 2/2] libbpf: xsk: move barriers from libbpf

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Message-ID: <0535ce9f-0db6-40f7-e512-e327f6f54c35@intel.com>
Date:   Thu, 11 Mar 2021 07:59:46 +0100
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Jonathan Lemon <jonathan.lemon@...il.com>,
        Björn Töpel <bjorn.topel@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org, andrii@...nel.org, magnus.karlsson@...el.com,
        maximmi@...dia.com, ciara.loftus@...el.com
Subject: Re: [PATCH bpf-next 2/2] libbpf: xsk: move barriers from
 libbpf_util.h to xsk.h

On 2021-03-11 01:06, Jonathan Lemon wrote:
> On Wed, Mar 10, 2021 at 09:09:29AM +0100, Björn Töpel wrote:
>> From: Björn Töpel <bjorn.topel@...el.com>
>>
>> The only user of libbpf_util.h is xsk.h. Move the barriers to xsk.h,
>> and remove libbpf_util.h. The barriers are used as an implementation
>> detail, and should not be considered part of the stable API.
> 
> Does that mean that anything else which uses the same type of
> shared rings (bpf ringbuffer, io_uring, zctap) have to implement
> the same primitives that xsk.h has?
> 

Jonathan, there's a longer explanation on back-/forward-compatibility in
the commit message [1]. Again, this is for the XDP socket rings, so I
wont comment on the other rings. I would not assume compatibility
between different rings (e.g. the bpf ringbuffer and XDP sockets rings),
not even prior the barrier change.


Björn

[1] 
https://lore.kernel.org/bpf/20210305094113.413544-2-bjorn.topel@gmail.com/