[v2,3/8] net/memif: relax the load of ring head pointer for M2S ring

Message ID 20200928190334.40624-3-honnappa.nagarahalli@arm.com
State New
Headers show
Series
  • [v2,1/8] net/memif: do not update local copy of tail in tx function
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Commit Message

Honnappa Nagarahalli Sept. 28, 2020, 7:03 p.m.
For M2S rings, ring->head is updated by the receiver and eth_memif_rx
function is called in the context of receiving thread. The loads in
the receiver do not need to synchronize with its own stores.

Fixes: a2aafb9aa651 ("net/memif: optimize with one-way barrier")
Cc: phil.yang@arm.com
Cc: stable@dpdk.org

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

Reviewed-by: Phil Yang <phil.yang@arm.com>

Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>

---
 drivers/net/memif/rte_eth_memif.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

-- 
2.17.1

Patch

diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c
index 8bacacaa8..159b45180 100644
--- a/drivers/net/memif/rte_eth_memif.c
+++ b/drivers/net/memif/rte_eth_memif.c
@@ -410,7 +410,11 @@  eth_memif_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 
 refill:
 	if (type == MEMIF_RING_M2S) {
-		head = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE);
+		/* ring->head is updated by the receiver and this function
+		 * is called in the context of receiver thread. The loads in
+		 * the receiver do not need to synchronize with its own stores.
+		 */
+		head = __atomic_load_n(&ring->head, __ATOMIC_RELAXED);
 		n_slots = ring_size - head + mq->last_tail;
 
 		while (n_slots--) {