Hi Stephan,
Thursday, August 2, 2018 1:00 AM, Stephen Hemminger:
> Subject: [RFC] mlx5: fix error unwind in device start
>
> The error handling in start of the mlx5 driver is buggy.
> For example, if setting up the flows fails the device driver will then get
> stuck
> in mlx5_flow_rxq_flags_clear waiting for something that will never happen.
Looking at the code I cannot understand why the mlx5_flow_rxq_flags_clear get
stuck nor to what it waits.
The function has few finite loops which are not depended in anything which
happened before it at the device start.
Moreover I tried to force either the mlx5_traffic_enable or the mlx5_flow_start
to stop, however the results was the port failed to start but no stuck.
Can you provide more details about the issue you saw there?
>
> The problem is that the code jumps to a common error label and does
> unwind for portions of the driver which have not been setup.
>
> This suggested patch breaks it into different labels with each failure path
> only
> unwinding what was done.
>
> Also, the ethdev driver should not be manipulating the dev_started flag
> directly. That is handled by the common ethdev layer.
>
I agree that maybe this code part can be better written, but my question before
is whether we have an actual bug that we will solve w/ this change?
> The patch works for the success case, but furthur testing is needed to
> actually exercise all the error paths.
> This is left as exercise for the maintainers.
>
> Signed-off-by: Stephen Hemminger <sthem...@microsoft.com>
> ---
> drivers/net/mlx5/mlx5_trigger.c | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/mlx5/mlx5_trigger.c
> b/drivers/net/mlx5/mlx5_trigger.c index e2a9bb703261..79a7b233986a
> 100644
> --- a/drivers/net/mlx5/mlx5_trigger.c
> +++ b/drivers/net/mlx5/mlx5_trigger.c
> @@ -171,42 +171,42 @@ mlx5_dev_start(struct rte_eth_dev *dev)
> if (ret) {
> DRV_LOG(ERR, "port %u Rx queue allocation failed: %s",
> dev->data->port_id, strerror(rte_errno));
> - mlx5_txq_stop(dev);
> - return -rte_errno;
> + goto error_txq_stop;
> }
> - dev->data->dev_started = 1;
> +
> ret = mlx5_rx_intr_vec_enable(dev);
> if (ret) {
> DRV_LOG(ERR, "port %u Rx interrupt vector creation failed",
> dev->data->port_id);
> - goto error;
> + goto error_rxq_stop;
> }
> mlx5_xstats_init(dev);
> ret = mlx5_traffic_enable(dev);
> if (ret) {
> DRV_LOG(DEBUG, "port %u failed to set defaults flows",
> dev->data->port_id);
> - goto error;
> + goto error_intr_vec_disable;
> }
> ret = mlx5_flow_start(dev, &priv->flows);
> if (ret) {
> DRV_LOG(DEBUG, "port %u failed to set flows",
> dev->data->port_id);
> - goto error;
> + goto error_traffic_disable;
> }
> +
> dev->tx_pkt_burst = mlx5_select_tx_function(dev);
> dev->rx_pkt_burst = mlx5_select_rx_function(dev);
> mlx5_dev_interrupt_handler_install(dev);
> return 0;
> -error:
> - ret = rte_errno; /* Save rte_errno before cleanup. */
> - /* Rollback. */
> - dev->data->dev_started = 0;
> - mlx5_flow_stop(dev, &priv->flows);
> +
> +error_traffic_disable:
> mlx5_traffic_disable(dev);
> - mlx5_txq_stop(dev);
> +error_intr_vec_disable:
> + mlx5_rx_intr_vec_disable(dev);
> +error_rxq_stop:
> mlx5_rxq_stop(dev);
> - rte_errno = ret; /* Restore rte_errno. */
> +error_txq_stop:
> + mlx5_txq_stop(dev);
> return -rte_errno;
> }
>
> --
> 2.18.0
