diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index 688ecb4c39f340d7dfb9002e73693775018a9ea2..402f3a20ec0aa7f4c50c1f6c74a41e12f9b6426c 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -489,6 +489,7 @@ static void *mlx4_ib_add(struct mlx4_dev *dev)
 	ibdev->uar_map = ioremap(ibdev->priv_uar.pfn << PAGE_SHIFT, PAGE_SIZE);
 	if (!ibdev->uar_map)
 		goto err_uar;
+	MLX4_INIT_DOORBELL_LOCK(&ibdev->uar_lock);
 
 	INIT_LIST_HEAD(&ibdev->pgdir_list);
 	mutex_init(&ibdev->pgdir_mutex);