vhost: fix async unregister deadlock

When async unregister function is invoked in certain vhost event
callbacks (e.g. vring state change), deadlock may occur due to
recursive spinlock acquire. This patch uses trylock() primitive in
the unregister API to avoid deadlock.

Fixes: 78639d54563a ("vhost: introduce async enqueue registration API")
Cc: stable@dpdk.org
Signed-off-by: Patrick Fu <patrick.fu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 3235658..6068c38 100644 (file)
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -1633,10 +1633,15 @@ int rte_vhost_async_channel_unregister(int vid, uint16_t queue_id)
                return ret;
 
        ret = 0;
-       rte_spinlock_lock(&vq->access_lock);
 
        if (!vq->async_registered)
-               goto out;
+               return ret;
+
+       if (!rte_spinlock_trylock(&vq->access_lock)) {
+               VHOST_LOG_CONFIG(ERR, "Failed to unregister async channel. "
+                       "virt queue busy.\n");
+               return -1;
+       }
 
        if (vq->async_pkts_inflight_n) {
                VHOST_LOG_CONFIG(ERR, "Failed to unregister async channel. "

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 1656ec7..d20c8c5 100644 (file)
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -1980,9 +1980,9 @@ vhost_user_set_vring_enable(struct virtio_net **pdev,
                "set queue enable: %d to qp idx: %d\n",
                enable, index);
 
-       if (!enable && dev->virtqueue[index]->async_registered) {
+       if (enable && dev->virtqueue[index]->async_registered) {
                if (dev->virtqueue[index]->async_pkts_inflight_n) {
-                       VHOST_LOG_CONFIG(ERR, "failed to disable vring. "
+                       VHOST_LOG_CONFIG(ERR, "failed to enable vring. "
                        "async inflight packets must be completed first\n");
                        return RTE_VHOST_MSG_RESULT_ERR;
                }