[PATCH 4/5] net/iavf: change no_poll flag to atomic

[Anurag Mandal]

The no_poll gate that pauses the Rx/Tx data path during reset and
link-down was a plain bool written on the control path and read on
the data-plane lcores without synchronization, allowing stale reads
that either keep dropping traffic or trigger spurious reset detection.

Made no_poll an RTE_ATOMIC(bool) and access it with release stores and
acquire loads so data-plane lcores reliably observe gate changes.

Fixes: 5b3124a0a6ef ("net/iavf: support no polling when link down")
Cc: stable at dpdk.org

Signed-off-by: Anurag Mandal <anurag.mandal at intel.com>
---
 drivers/net/intel/iavf/iavf.h        | 2 +-
 drivers/net/intel/iavf/iavf_ethdev.c | 6 +++++-
 drivers/net/intel/iavf/iavf_rxtx.c   | 8 ++++++--
 drivers/net/intel/iavf/iavf_vchnl.c  | 4 +++-
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/net/intel/iavf/iavf.h b/drivers/net/intel/iavf/iavf.h
index e76c3bb410..037bc8436f 100644
--- a/drivers/net/intel/iavf/iavf.h
+++ b/drivers/net/intel/iavf/iavf.h
@@ -392,7 +392,7 @@ struct iavf_adapter {
 	alignas(RTE_CACHE_LINE_MIN_SIZE) uint32_t ptype_tbl[IAVF_MAX_PKT_TYPE];
 	bool stopped;
 	bool closed;
-	bool no_poll;
+	RTE_ATOMIC(bool)no_poll;
 	enum iavf_rx_func_type rx_func_type;
 	enum iavf_tx_func_type tx_func_type;
 	uint16_t fdir_ref_cnt;
diff --git a/drivers/net/intel/iavf/iavf_ethdev.c b/drivers/net/intel/iavf/iavf_ethdev.c
index 87b826c873..f6ce339b0c 100644
--- a/drivers/net/intel/iavf/iavf_ethdev.c
+++ b/drivers/net/intel/iavf/iavf_ethdev.c
@@ -3604,9 +3604,13 @@ void
 iavf_set_no_poll(struct iavf_adapter *adapter, bool link_change)
 {
 	struct iavf_info *vf = &adapter->vf;
+	bool no_poll;
 
-	adapter->no_poll = (link_change & !vf->link_up) ||
+	no_poll = (link_change & !vf->link_up) ||
 		vf->vf_reset || vf->in_reset_recovery;
+
+	rte_atomic_store_explicit(&adapter->no_poll, no_poll,
+				  rte_memory_order_release);
 }
 
 static int
diff --git a/drivers/net/intel/iavf/iavf_rxtx.c b/drivers/net/intel/iavf/iavf_rxtx.c
index 931bb8420d..104197d082 100644
--- a/drivers/net/intel/iavf/iavf_rxtx.c
+++ b/drivers/net/intel/iavf/iavf_rxtx.c
@@ -3723,7 +3723,9 @@ iavf_recv_pkts_no_poll(void *rx_queue, struct rte_mbuf **rx_pkts,
 	struct ci_rx_queue *rxq = rx_queue;
 	enum iavf_rx_func_type rx_func_type;
 
-	if (!rxq->iavf_vsi || rxq->iavf_vsi->adapter->no_poll)
+	if (!rxq->iavf_vsi ||
+	    rte_atomic_load_explicit(&rxq->iavf_vsi->adapter->no_poll,
+				     rte_memory_order_acquire))
 		return 0;
 
 	rx_func_type = rxq->iavf_vsi->adapter->rx_func_type;
@@ -3739,7 +3741,9 @@ iavf_xmit_pkts_no_poll(void *tx_queue, struct rte_mbuf **tx_pkts,
 	struct ci_tx_queue *txq = tx_queue;
 	enum iavf_tx_func_type tx_func_type;
 
-	if (!txq->iavf_vsi || txq->iavf_vsi->adapter->no_poll)
+	if (!txq->iavf_vsi ||
+	    rte_atomic_load_explicit(&txq->iavf_vsi->adapter->no_poll,
+				     rte_memory_order_acquire))
 		return 0;
 
 	tx_func_type = txq->iavf_vsi->adapter->tx_func_type;
diff --git a/drivers/net/intel/iavf/iavf_vchnl.c b/drivers/net/intel/iavf/iavf_vchnl.c
index d22990a524..dee76f97cb 100644
--- a/drivers/net/intel/iavf/iavf_vchnl.c
+++ b/drivers/net/intel/iavf/iavf_vchnl.c
@@ -268,7 +268,9 @@ iavf_handle_link_change_event(struct rte_eth_dev *dev,
 	if (adapter->devargs.no_poll_on_link_down) {
 		iavf_set_no_poll(adapter, true);
 		PMD_DRV_LOG(DEBUG, "VF no poll turned %s",
-			    adapter->no_poll ? "on" : "off");
+			    rte_atomic_load_explicit(&adapter->no_poll,
+						     rte_memory_order_relaxed) ?
+						     "on" : "off");
 		if (!vf->link_up)
 			iavf_dev_tx_drain(dev);
 	}
-- 
2.34.1