[dpdk-dev] [PATCH v2 1/1] net/tap: fix blocked rx packets error

[Marcin Smoczynski]

When OS sends more packets than are being read with a single
'rte_eth_rx_burst' call, rx packets are getting stucked in the tap pmd
and are unable to receive, because trigger_seen is getting updated
and consecutive calls are not getting any packets.

Do not update trigger_seen unless less than a max number of packets were
received allowing next call to receive the rest.

Remove unnecessary compiler barrier.

Fixes: a0d8e807d9 ("net/tap: add Rx trigger")
Cc: stable at dpdk.org

Tested-by: Mariusz Drost <mariuszx.drost at intel.com>
Tested-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
Signed-off-by: Marcin Smoczynski <marcinx.smoczynski at intel.com>
---
 drivers/net/tap/rte_eth_tap.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 64bd04911..9c3adb832 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -353,10 +353,8 @@ pmd_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 
 	if (trigger == rxq->trigger_seen)
 		return 0;
-	if (trigger)
-		rxq->trigger_seen = trigger;
+
 	process_private = rte_eth_devices[rxq->in_port].process_private;
-	rte_compiler_barrier();
 	for (num_rx = 0; num_rx < nb_pkts; ) {
 		struct rte_mbuf *mbuf = rxq->pool;
 		struct rte_mbuf *seg = NULL;
@@ -433,6 +431,9 @@ pmd_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	rxq->stats.ipackets += num_rx;
 	rxq->stats.ibytes += num_rx_bytes;
 
+	if (trigger && num_rx < nb_pkts)
+		rxq->trigger_seen = trigger;
+
 	return num_rx;
 }
 
-- 
2.17.1