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

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