Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Shi, Yang
2015-11-11T00:26:07Z

On 11/10/2015 4:08 PM, Eric Dumazet wrote:
> On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote:
>> aarch64 doesn't have native support for XADD instruction, implement it by
>> the below instruction sequence:
>>
>> Load (dst + off) to a register
>> Add src to it
>> Store it back to (dst + off)
>
> Not really what is needed ?
>
> See this BPF_XADD as an atomic_add() equivalent.

I see. Thanks. The documentation doesn't say too much about "exclusive"
add. If so it should need load-acquire/store-release.

I will rework it.

Yang

>
>