[dpdk-dev] [PATCH] net/mlx5: handle expected errno properly

[Xiaoyu Min <jackmin@mellanox.com>]

rte_errno is a per thread variable and is widely used as an
error indicator, which means a function could affect
other functions' results by setting rte_errno carelessly

During rxq setup, an EINVAL rte_errno is expected since
the queues are not created yet
So rte_errno is cleared when it is EINVAL as expected

Signed-off-by: Xiaoyu Min <jackmin@mellanox.com>
---
 drivers/net/mlx5/mlx5_rxq.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index 1f7bfd4..e7056e8 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -443,6 +443,7 @@
 	struct mlx5_rxq_data *rxq = (*priv->rxqs)[idx];
 	struct mlx5_rxq_ctrl *rxq_ctrl =
 		container_of(rxq, struct mlx5_rxq_ctrl, rxq);
+	int ret = 0;
 
 	if (!rte_is_power_of_2(desc)) {
 		desc = 1 << log2above(desc);
@@ -459,13 +460,21 @@
 		rte_errno = EOVERFLOW;
 		return -rte_errno;
 	}
-	if (!mlx5_rxq_releasable(dev, idx)) {
+	ret = mlx5_rxq_releasable(dev, idx);
+	if (!ret) {
 		DRV_LOG(ERR, "port %u unable to release queue index %u",
 			dev->data->port_id, idx);
 		rte_errno = EBUSY;
 		return -rte_errno;
+	} else if (ret == -EINVAL) {
+		/**
+		 * on the first time, rx queue doesn't exist,
+		 * so just ignore this error and reset rte_errno.
+		 */
+		rte_errno = 0;
+	} else {
+		mlx5_rxq_release(dev, idx);
 	}
-	mlx5_rxq_release(dev, idx);
 	rxq_ctrl = mlx5_rxq_new(dev, idx, desc, socket, conf, mp);
 	if (!rxq_ctrl) {
 		DRV_LOG(ERR, "port %u unable to allocate queue index %u",
@@ -1543,11 +1552,12 @@ struct mlx5_rxq_ctrl *
  * @param dev
  *   Pointer to Ethernet device.
  * @param idx
- *   TX queue index.
+ *   RX queue index.
  *
  * @return
- *   1 if the queue can be released, negative errno otherwise and rte_errno is
- *   set.
+ *   1 if the queue can be released
+ *   0 if the queue can not be released
+ *   -EINVAL if the queue doesn't exist
  */
 int
 mlx5_rxq_releasable(struct rte_eth_dev *dev, uint16_t idx)
-- 
1.8.3.1