Re: [dpdk-stable] [dpdk-dev] [PATCH] net/mlx5: fix debug log segfault on TxQ release

[Matan Azrad <matan@mellanox.com>]

From: Alexander Kozyrev
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000008ef7c4 in mlx5_tx_queue_release (dpdk_txq=0x17ce01680) at
> drivers/net/mlx5/mlx5_txq.c:302
> 301 mlx5_txq_release(ETH_DEV(priv), i);
> 302 DRV_LOG(DEBUG, "port %u removing Tx queue %u from list",
> 303         PORT_ID(priv), txq->idx);
> The problem is txq is freed inside the mlx5_txq_release() function and no
> longer valid in the debug log right after this invocation.
> Move the debug log before the mlx5_txq_release() function to fix this.
> 
> Fixes: a6d83b6a92 ("net/mlx5: standardize on negative errno values")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Alexander Kozyrev <akozyrev@mellanox.com>

Good catch.

Better title:
net/mlx5: fix TxQ release debug log timing

In general, we prefer that the fix title points to the root cause and not to the consequences.

Besides it,
Acked-by: Matan Azrad <matan@mellanox.com>

> ---
>  drivers/net/mlx5/mlx5_txq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/mlx5/mlx5_txq.c b/drivers/net/mlx5/mlx5_txq.c
> index 29e5cab..a211fa9 100644
> --- a/drivers/net/mlx5/mlx5_txq.c
> +++ b/drivers/net/mlx5/mlx5_txq.c
> @@ -298,9 +298,9 @@
>  	priv = txq_ctrl->priv;
>  	for (i = 0; (i != priv->txqs_n); ++i)
>  		if ((*priv->txqs)[i] == txq) {
> -			mlx5_txq_release(ETH_DEV(priv), i);
>  			DRV_LOG(DEBUG, "port %u removing Tx queue %u
> from list",
>  				PORT_ID(priv), txq->idx);
> +			mlx5_txq_release(ETH_DEV(priv), i);
>  			break;
>  		}
>  }
> --
> 1.8.3.1