[PATCH v2] net/vhost: fix deadlock on vring state change

[Yuan Wang]

If vring state changes after pmd starts working, the locked vring
notifies pmd, thus calling update_queuing_status(), the latter
will wait for pmd to finish accessing vring, while pmd is also
waiting for vring to be unlocked, thus causing deadlock.

Actually, update_queuing_status() only needs to wait while
destroy/stopping the device, but not in other cases.

This patch adds a flag for whether or not to wait to fix this issue.

Fixes: 1ce3c7fe149f ("net/vhost: emulate device start/stop behavior")
Cc: stable at dpdk.org

Signed-off-by: Yuan Wang <yuanx.wang at intel.com>
---
V2: rewrite the commit log.
---
 drivers/net/vhost/rte_eth_vhost.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
index d75d256040..7e512d94bf 100644
--- a/drivers/net/vhost/rte_eth_vhost.c
+++ b/drivers/net/vhost/rte_eth_vhost.c
@@ -741,7 +741,7 @@ eth_vhost_install_intr(struct rte_eth_dev *dev)
 }
 
 static void
-update_queuing_status(struct rte_eth_dev *dev)
+update_queuing_status(struct rte_eth_dev *dev, bool wait_queuing)
 {
 	struct pmd_internal *internal = dev->data->dev_private;
 	struct vhost_queue *vq;
@@ -767,7 +767,7 @@ update_queuing_status(struct rte_eth_dev *dev)
 			rte_atomic32_set(&vq->allow_queuing, 1);
 		else
 			rte_atomic32_set(&vq->allow_queuing, 0);
-		while (rte_atomic32_read(&vq->while_queuing))
+		while (wait_queuing && rte_atomic32_read(&vq->while_queuing))
 			rte_pause();
 	}
 
@@ -779,7 +779,7 @@ update_queuing_status(struct rte_eth_dev *dev)
 			rte_atomic32_set(&vq->allow_queuing, 1);
 		else
 			rte_atomic32_set(&vq->allow_queuing, 0);
-		while (rte_atomic32_read(&vq->while_queuing))
+		while (wait_queuing && rte_atomic32_read(&vq->while_queuing))
 			rte_pause();
 	}
 }
@@ -868,7 +868,7 @@ new_device(int vid)
 	vhost_dev_csum_configure(eth_dev);
 
 	rte_atomic32_set(&internal->dev_attached, 1);
-	update_queuing_status(eth_dev);
+	update_queuing_status(eth_dev, false);
 
 	VHOST_LOG(INFO, "Vhost device %d created\n", vid);
 
@@ -898,7 +898,7 @@ destroy_device(int vid)
 	internal = eth_dev->data->dev_private;
 
 	rte_atomic32_set(&internal->dev_attached, 0);
-	update_queuing_status(eth_dev);
+	update_queuing_status(eth_dev, true);
 
 	eth_dev->data->dev_link.link_status = RTE_ETH_LINK_DOWN;
 
@@ -1008,7 +1008,7 @@ vring_state_changed(int vid, uint16_t vring, int enable)
 	state->max_vring = RTE_MAX(vring, state->max_vring);
 	rte_spinlock_unlock(&state->lock);
 
-	update_queuing_status(eth_dev);
+	update_queuing_status(eth_dev, false);
 
 	VHOST_LOG(INFO, "vring%u is %s\n",
 			vring, enable ? "enabled" : "disabled");
@@ -1197,7 +1197,7 @@ eth_dev_start(struct rte_eth_dev *eth_dev)
 	}
 
 	rte_atomic32_set(&internal->started, 1);
-	update_queuing_status(eth_dev);
+	update_queuing_status(eth_dev, false);
 
 	return 0;
 }
@@ -1209,7 +1209,7 @@ eth_dev_stop(struct rte_eth_dev *dev)
 
 	dev->data->dev_started = 0;
 	rte_atomic32_set(&internal->started, 0);
-	update_queuing_status(dev);
+	update_queuing_status(dev, true);
 
 	return 0;
 }
-- 
2.25.1