[PATCH] vhost: fix deadlock when vhost unregister

[sunwenjie <findtheonlyway@gmail.com>]

When rte_vhost_driver_unregister  delete the connection fd,
fdset_try_del will always try and donot release the
vhostuser.mutex if the fd is busy, but the fdset_event_dispatch
will set the  fd to busy and call vhost_user_msg_handler to get
vhostuser.mutex, which will  cause deadlock. Unlock the
vhost_user.mutexif fdset_try_del fail and relock it when retry.

Fixes: 8b4b949144b8 ("vhost: fix dead lock on closing in server mode")
Cc: stable@dpdk.org

Signed-off-by: sunwenjie <findtheonlyway@gmail.com>
---
 lib/librte_vhost/socket.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index 9cf34ad17..9883b0491 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -961,13 +961,13 @@ rte_vhost_driver_unregister(const char *path)
 	int count;
 	struct vhost_user_connection *conn, *next;
 
+again:
 	pthread_mutex_lock(&vhost_user.mutex);
 
 	for (i = 0; i < vhost_user.vsocket_cnt; i++) {
 		struct vhost_user_socket *vsocket = vhost_user.vsockets[i];
 
 		if (!strcmp(vsocket->path, path)) {
-again:
 			pthread_mutex_lock(&vsocket->conn_mutex);
 			for (conn = TAILQ_FIRST(&vsocket->conn_list);
 			     conn != NULL;
@@ -983,6 +983,7 @@ rte_vhost_driver_unregister(const char *path)
 						  conn->connfd) == -1) {
 					pthread_mutex_unlock(
 							&vsocket->conn_mutex);
+					pthread_mutex_unlock(&vhost_user.mutex);
 					goto again;
 				}
 
-- 
2.20.1