[PATCH] net/mlx5: fix null derefrence in mlx5 txq start

[Weiguo Li]

Pointer 'txq_ctrl' was dereferenced and then compared to NULL.
Change the order to keep the logic consistent.

Fixes: f49f44839df3 ("net/mlx5: share Tx control code")
Cc: stable at dpdk.org

Signed-off-by: Weiguo Li <liweiguo at xencore.cn>
---
 drivers/net/mlx5/mlx5_trigger.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/mlx5_trigger.c b/drivers/net/mlx5/mlx5_trigger.c
index 7bdb897612..0741bf627d 100644
--- a/drivers/net/mlx5/mlx5_trigger.c
+++ b/drivers/net/mlx5/mlx5_trigger.c
@@ -54,11 +54,14 @@ mlx5_txq_start(struct rte_eth_dev *dev)
 
 	for (i = 0; i != priv->txqs_n; ++i) {
 		struct mlx5_txq_ctrl *txq_ctrl = mlx5_txq_get(dev, i);
-		struct mlx5_txq_data *txq_data = &txq_ctrl->txq;
+		struct mlx5_txq_data *txq_data;
 		uint32_t flags = MLX5_MEM_RTE | MLX5_MEM_ZERO;
 
 		if (!txq_ctrl)
 			continue;
+
+		txq_data = &txq_ctrl->txq;
+
 		if (!txq_ctrl->is_hairpin)
 			txq_alloc_elts(txq_ctrl);
 		MLX5_ASSERT(!txq_ctrl->obj);
-- 
2.34.1