Re: [dpdk-dev] [PATCH v2] net/failsafe: fix tx sub device deactivating

["Gaëtan Rivet" <gaetan.rivet@6wind.com>]

On Wed, Aug 16, 2017 at 05:19:28PM +0300, Matan Azrad wrote:
> The corrupted code couldn't recognize that all sub devices
> were not ready for tx traffic when failsafe PMD was trying
> to switch device because of an unreachable condition using.
> 
> Hence, the current tx sub device variable was not updated
> correctly.
> 
> The fix removed the unreachable branch and added new one
> in the right place respecting the original intent.
> 
> Fixes: ebea83f899d8 ("net/failsafe: add plug-in support")
> Fixes: 598fb8aec6f6 ("net/failsafe: support device removal")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Matan Azrad <matan@mellanox.com>
> Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> ---
>  drivers/net/failsafe/failsafe_private.h | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/failsafe/failsafe_private.h b/drivers/net/failsafe/failsafe_private.h
> index 0361cf4..ef646db 100644
> --- a/drivers/net/failsafe/failsafe_private.h
> +++ b/drivers/net/failsafe/failsafe_private.h
> @@ -334,7 +334,7 @@ fs_switch_dev(struct rte_eth_dev *dev,
>  	} else if ((txd && txd->state < req_state) ||
>  		   txd == NULL ||
>  		   txd == banned) {
> -		struct sub_device *sdev;
> +		struct sub_device *sdev = NULL;

Good catch, actually this makes me think that the FOREACH_SUBDEV_STATE
macro is not following the usual tailq API (which sets the iterator to
NULL upon terminating). This can throw-off the unsuspecting writer.

I will fix this soon™. In the meantime, sdev should be initialized to
NULL.

>  		uint8_t i;
>  
>  		/* Using acceptable device */
> @@ -346,9 +346,10 @@ fs_switch_dev(struct rte_eth_dev *dev,
>  			PRIV(dev)->subs_tx = i;
>  			break;
>  		}
> -	} else if (txd && txd->state < req_state) {
> -		DEBUG("No device ready, deactivating tx_dev");
> -		PRIV(dev)->subs_tx = PRIV(dev)->subs_tail;
> +		if (i >= PRIV(dev)->subs_tail || sdev == NULL) {
> +			DEBUG("No device ready, deactivating tx_dev");
> +			PRIV(dev)->subs_tx = PRIV(dev)->subs_tail;
> +		}
>  	} else {
>  		return;
>  	}
> -- 
> 2.7.4
> 

-- 
Gaëtan Rivet
6WIND