[RFC 1/3] net/cnxk: add pause to spinloops

[Stephen Hemminger]

On SMT systems when a spinloop is done without a pause
it may cause excessive latency. This problem was found
by the fix_empty_spinloops coccinelle script.

This is compile tested only! I don't have this hardware.

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
 drivers/net/cnxk/cn10k_tx.h | 4 ++--
 drivers/net/cnxk/cn20k_tx.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/cnxk/cn10k_tx.h b/drivers/net/cnxk/cn10k_tx.h
index be9e020ac5..3f4cad168c 100644
--- a/drivers/net/cnxk/cn10k_tx.h
+++ b/drivers/net/cnxk/cn10k_tx.h
@@ -167,7 +167,7 @@ cn10k_nix_vwqe_wait_fc(struct cn10k_eth_txq *txq, uint16_t req)
 #else
 	RTE_SET_USED(pkts);
 	while (rte_atomic_load_explicit(&txq->fc_cache_pkts, rte_memory_order_relaxed) < 0)
-		;
+		rte_pause();
 #endif
 	cached = rte_atomic_fetch_sub_explicit(&txq->fc_cache_pkts, req, rte_memory_order_acquire) -
 		 req;
@@ -402,7 +402,7 @@ cn10k_nix_sec_fc_wait(struct cn10k_eth_txq *txq, uint16_t nb_pkts)
 #else
 	/* Wait for primary core to refill FC. */
 	while (rte_atomic_load_explicit(fc_sw, rte_memory_order_relaxed) < 0)
-		;
+		rte_pause();
 #endif
 
 	val = rte_atomic_fetch_sub_explicit(fc_sw, nb_pkts, rte_memory_order_acquire) - nb_pkts;
diff --git a/drivers/net/cnxk/cn20k_tx.h b/drivers/net/cnxk/cn20k_tx.h
index 9e48744831..3dfad5fd5a 100644
--- a/drivers/net/cnxk/cn20k_tx.h
+++ b/drivers/net/cnxk/cn20k_tx.h
@@ -165,7 +165,7 @@ cn20k_nix_vwqe_wait_fc(struct cn20k_eth_txq *txq, uint16_t req)
 #else
 	RTE_SET_USED(pkts);
 	while (rte_atomic_load_explicit(&txq->fc_cache_pkts, rte_memory_order_relaxed) < 0)
-		;
+		rte_pause();
 #endif
 	cached = rte_atomic_fetch_sub_explicit(&txq->fc_cache_pkts, req, rte_memory_order_acquire) -
 		 req;
@@ -392,7 +392,7 @@ cn20k_nix_sec_fc_wait(struct cn20k_eth_txq *txq, uint16_t nb_pkts)
 #else
 	/* Wait for primary core to refill FC. */
 	while (rte_atomic_load_explicit(fc_sw, rte_memory_order_relaxed) < 0)
-		;
+		rte_pause();
 #endif
 
 	val = rte_atomic_fetch_sub_explicit(fc_sw, nb_pkts, rte_memory_order_acquire) - nb_pkts;
-- 
2.51.0