Re: [PATCH 9/9] bpf: make callback handle atomic with relaxed access

[Stephen Hemminger <stephen@networkplumber.org>]

On Sun, 11 Oct 2026 18:21:57 +0000
Marat Khalili <qm2k21@gmail.com> wrote:

> The callback handle member cb of struct bpf_eth_cbi is concurrently
> cleared by the control plane on unload and read by the datapath to
> decide whether to execute the BPF filter program. Without atomic typing,
> this concurrent access constitutes a data race in the C11 memory model,
> even though hardware pointer accesses are single-copy atomic and untorn.
> 
> Change cb to RTE_ATOMIC and use rte_atomic_load_explicit() and
> rte_atomic_store_explicit() with rte_memory_order_relaxed for all its
> accesses. On modern architectures this produces the exact same machine
> code while eliminating undefined behavior.
> 
> In addition, marking cb as atomic improves code self-documentation by
> making it immediately evident that cb is an active part of the cross-
> thread synchronization mechanism on par with use.
> 
> Signed-off-by: Marat Khalili <qm2k21@gmail.com>
> ---

Since inuse and cb are inter-related would be easier to squash the mb
conversion and the bool and the atomic cb into one patch.