[PATCH 8/9] bpf: use relaxed stores for callback inuse tracking

[Marat Khalili <qm2k21@gmail.com>]

Direct assignment to an atomic variable defaults to sequentially
consistent memory order in C11. Since cross-thread memory ordering
for packet callback execution and unload is already explicitly
enforced by memory barriers, sequentially consistent stores are
unnecessary and may emit redundant barrier instructions on weakly
ordered architectures.

Update bpf_eth_cbi_inuse() and bpf_eth_cbi_unuse() to use
rte_atomic_store_explicit() with rte_memory_order_relaxed, matching
the relaxed loads already used in bpf_eth_cbi_wait().

Signed-off-by: Marat Khalili <qm2k21@gmail.com>
---
 lib/bpf/bpf_pkt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/bpf/bpf_pkt.c b/lib/bpf/bpf_pkt.c
index ea7e240494..9dee001f0f 100644
--- a/lib/bpf/bpf_pkt.c
+++ b/lib/bpf/bpf_pkt.c
@@ -137,7 +137,7 @@ static struct bpf_eth_cbh tx_cbh = {
 static __rte_always_inline void
 bpf_eth_cbi_inuse(struct bpf_eth_cbi *cbi)
 {
-	cbi->use = BPF_ETH_CBI_INUSE;
+	rte_atomic_store_explicit(&cbi->use, BPF_ETH_CBI_INUSE, rte_memory_order_relaxed);
 	/* make sure no store/load reordering could happen */
 	rte_smp_mb();
 }
@@ -150,7 +150,7 @@ bpf_eth_cbi_unuse(struct bpf_eth_cbi *cbi)
 {
 	/* make sure all previous loads are completed */
 	rte_smp_rmb();
-	cbi->use = 0;
+	rte_atomic_store_explicit(&cbi->use, 0, rte_memory_order_relaxed);
 }
 
 /*
-- 
2.43.0