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

[Gaëtan Rivet]

Hi Matan,

Thanks for spotting this, a few nits below.

On Tue, Aug 15, 2017 at 09:59:19AM +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 condition and adds condition
> in the right place to handle non tx device ready scenario.
> 

It should be reworded as

  Make the condition reachable by moving it in the right place to
  handle the scenario when no TX device is ready.

If the condition is removed and then added, I find it clearer to say
that it was moved.

> Fixes: ebea83f899d8 ("net/failsafe: add plug-in support")
> Fixes: 598fb8aec6f6 ("net/failsafe: support device removal")
> 

The root commit introducing the issue is the first one, but
this fix only applies to the second.
So I don't know which commit is actually fixed by this, but I find
peculiar to have two commits targeted by a fix.

In doubt, probably leave both, but maybe someone has a better idea about
it?

> Signed-off-by: Matan Azrad <matan at mellanox.com>
> Cc: stable at dpdk.org

The Cc: stable line should immediately follow the Fixes: line.

> ---
>  drivers/net/failsafe/failsafe_private.h | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> Hi Gaetan
> I didn't find any real scenario which cause to problematic
> behavior because of the previous code.
> But it may be.    
> 
> diff --git a/drivers/net/failsafe/failsafe_private.h b/drivers/net/failsafe/failsafe_private.h
> index 0361cf4..dc97aec 100644
> --- a/drivers/net/failsafe/failsafe_private.h
> +++ b/drivers/net/failsafe/failsafe_private.h
> @@ -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) {

`!sdev` should be `sdev == NULL`, see [1].

> +			DEBUG("No device ready, deactivating tx_dev");
> +			PRIV(dev)->subs_tx = PRIV(dev)->subs_tail;
> +		}
>  	} else {
>  		return;
>  	}
> -- 
> 2.7.4
> 

With these changes,

Acked-by: Gaetan Rivet <gaetan.rivet at 6wind.com>

[1]:
http://dpdk.org/doc/guides/contributing/coding_style.html#c-statement-style-and-conventions
-- 
Gaëtan Rivet
6WIND