On 3/2/21 9:05 AM, Björn Töpel wrote:
On 2021-03-01 17:10, Toke Høiland-Jørgensen wrote:
Björn Töpel <bjorn.topel@xxxxxxxxx> writes:
From: Björn Töpel <bjorn.topel@xxxxxxxxx>
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)?
"This is fine." ;-) This was briefly discussed in [1], outlined by the
previous commit!
...even on POWER.
Could you put a summary or quote of that discussion on 'why it is okay and does not
cause /forward or backward/ compat issues with user space' directly into patch 1's
commit message?
I feel just referring to a link is probably less suitable in this case as it should
rather be part of the commit message that contains the justification on why it is
waterproof - at least it feels that specific area may be a bit under-documented, so
having it as direct part certainly doesn't hurt.
Would also be great to get Will's ACK on that when you have a v2. :)
Thanks,
Daniel
[1] https://lore.kernel.org/bpf/20200316184423.GA14143@willie-the-truck/
