Re: [PATCH bpf-next v4 10/10] bpf, docs: Update instruction-set.rst for load-acquire and store-release instructions

Alexei Starovoitov
2025-03-03T19:15:00Z

On Sun, Mar 2, 2025 at 9:38 PM Peilin Ye <yepeilin@google.com> wrote:
>
> Update documentation for the new load-acquire and store-release
> instructions. Rename existing atomic operations as "atomic
> read-modify-write (RMW) operations".

rmw renaming looks like a churn. I don't think it adds clarity.

> Following RFC 9669, section 7.3. "Adding Instructions", create new
> conformance groups "atomic32v2" and "atomic64v2", where:
>
> * atomic32v2: includes all instructions in "atomic32", plus the new
> 8-bit, 16-bit and 32-bit atomic load-acquire and
> store-release instructions
>
> * atomic64v2: includes all instructions in "atomic64" and
> "atomic32v2", plus the new 64-bit atomic load-acquire
> and store-release instructions

I think it's better for new groups to include only newly added insns.
Also we probably should add barriers to kernel/llvm and only
then update the doc with all insns together.
Otherwise we very quickly get to atomicv3 and v4 groups.
Naming wise I would call these two insns plus all barriers as
barrier32 and barrier64 groups.
cmpwait insn should probably be there as well.