[PATCH v9 21/25] net/vhost: use stdatomic for state flags

[Stephen Hemminger]

The flags started and dev_attached are consulted only inside
update_queuing_status, where the per-queue handshake provides the
real synchronization; their loads and stores are relaxed.

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
 drivers/net/vhost/rte_eth_vhost.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
index 56c7a973e9..07d3d15781 100644
--- a/drivers/net/vhost/rte_eth_vhost.c
+++ b/drivers/net/vhost/rte_eth_vhost.c
@@ -86,14 +86,14 @@ struct vhost_queue {
 };
 
 struct pmd_internal {
-	rte_atomic32_t dev_attached;
+	RTE_ATOMIC(uint32_t) dev_attached;
 	char *iface_name;
 	uint64_t flags;
 	uint64_t disable_flags;
 	uint64_t features;
 	uint16_t max_queues;
 	int vid;
-	rte_atomic32_t started;
+	RTE_ATOMIC(uint32_t) started;
 	bool vlan_strip;
 	bool rx_sw_csum;
 	bool tx_sw_csum;
@@ -756,8 +756,12 @@ update_queuing_status(struct rte_eth_dev *dev, bool wait_queuing)
 	if (!dev->data->rx_queues || !dev->data->tx_queues)
 		return;
 
-	if (rte_atomic32_read(&internal->started) == 0 ||
-	    rte_atomic32_read(&internal->dev_attached) == 0)
+	/* These are control-plane flags consulted only here;
+	 * the real data-path handshake is on vq->allow_queuing below.
+	 * Relaxed is sufficient.
+	 */
+	if (rte_atomic_load_explicit(&internal->started, rte_memory_order_relaxed) == 0 ||
+	    rte_atomic_load_explicit(&internal->dev_attached, rte_memory_order_relaxed) == 0)
 		allow_queuing = 0;
 
 	state = vring_states[dev->data->port_id];
@@ -848,7 +852,7 @@ new_device(int vid)
 	}
 
 	internal->vid = vid;
-	if (rte_atomic32_read(&internal->started) == 1) {
+	if (rte_atomic_load_explicit(&internal->started, rte_memory_order_relaxed) == 1) {
 		queue_setup(eth_dev, internal);
 		if (dev_conf->intr_conf.rxq)
 			eth_vhost_configure_intr(eth_dev);
@@ -863,7 +867,7 @@ new_device(int vid)
 
 	vhost_dev_csum_configure(eth_dev);
 
-	rte_atomic32_set(&internal->dev_attached, 1);
+	rte_atomic_store_explicit(&internal->dev_attached, 1, rte_memory_order_relaxed);
 	update_queuing_status(eth_dev, false);
 
 	VHOST_LOG_LINE(INFO, "Vhost device %d created", vid);
@@ -893,7 +897,7 @@ destroy_device(int vid)
 	eth_dev = list->eth_dev;
 	internal = eth_dev->data->dev_private;
 
-	rte_atomic32_set(&internal->dev_attached, 0);
+	rte_atomic_store_explicit(&internal->dev_attached, 0, rte_memory_order_relaxed);
 	update_queuing_status(eth_dev, true);
 	eth_vhost_unconfigure_intr(eth_dev);
 
@@ -1148,11 +1152,11 @@ eth_dev_start(struct rte_eth_dev *eth_dev)
 	}
 
 	queue_setup(eth_dev, internal);
-	if (rte_atomic32_read(&internal->dev_attached) == 1 &&
+	if (rte_atomic_load_explicit(&internal->dev_attached, rte_memory_order_relaxed) == 1 &&
 			dev_conf->intr_conf.rxq)
 		eth_vhost_configure_intr(eth_dev);
 
-	rte_atomic32_set(&internal->started, 1);
+	rte_atomic_store_explicit(&internal->started, 1, rte_memory_order_relaxed);
 	update_queuing_status(eth_dev, false);
 
 	for (i = 0; i < eth_dev->data->nb_rx_queues; i++)
@@ -1170,7 +1174,7 @@ eth_dev_stop(struct rte_eth_dev *dev)
 	uint16_t i;
 
 	dev->data->dev_started = 0;
-	rte_atomic32_set(&internal->started, 0);
+	rte_atomic_store_explicit(&internal->started, 0, rte_memory_order_relaxed);
 	update_queuing_status(dev, true);
 
 	for (i = 0; i < dev->data->nb_rx_queues; i++)
@@ -1469,8 +1473,10 @@ vhost_dev_priv_dump(struct rte_eth_dev *dev, FILE *f)
 	fprintf(f, "features: 0x%" PRIx64 "\n", internal->features);
 	fprintf(f, "max_queues: %u\n", internal->max_queues);
 	fprintf(f, "vid: %d\n", internal->vid);
-	fprintf(f, "started: %d\n", rte_atomic32_read(&internal->started));
-	fprintf(f, "dev_attached: %d\n", rte_atomic32_read(&internal->dev_attached));
+	fprintf(f, "started: %u\n",
+		rte_atomic_load_explicit(&internal->started, rte_memory_order_relaxed));
+	fprintf(f, "dev_attached: %u\n",
+		rte_atomic_load_explicit(&internal->dev_attached, rte_memory_order_relaxed));
 	fprintf(f, "vlan_strip: %d\n", internal->vlan_strip);
 	fprintf(f, "rx_sw_csum: %d\n", internal->rx_sw_csum);
 	fprintf(f, "tx_sw_csum: %d\n", internal->tx_sw_csum);
-- 
2.53.0