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

[Matan Azrad <matan@mellanox.com>]

Hi Gaetan

> -----Original Message-----
> From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
> Sent: Wednesday, August 16, 2017 11:47 AM
> To: Matan Azrad <matan@mellanox.com>
> Cc: dev@dpdk.org; stable@dpdk.org
> Subject: Re: [PATCH] net/failsafe: fix tx sub device deactivating
> 
> 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.

But the two conditions are different,
The old condition can't handle the scenario we want.
	
> 
> > 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?

I also thought about it, and found the two are necessary for future review. 
 
> 
> > Signed-off-by: Matan Azrad <matan@mellanox.com>
> > Cc: stable@dpdk.org
> 
> The Cc: stable line should immediately follow the Fixes: line.
> 

Will be fixed.

> > ---
> >  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].
OK, will be fixed.

> 
> > +			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@6wind.com>
> 
> [1]:
> https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdpd
> k.org%2Fdoc%2Fguides%2Fcontributing%2Fcoding_style.html%23c-
> statement-style-and-
> conventions&data=02%7C01%7Cmatan%40mellanox.com%7C6283c71dcc2b4
> ebe5f6608d4e48350cd%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%
> 7C636384700025293702&sdata=nNMTElzhe3RlEMc3vB67QlwAYYYQ%2ByNNp
> 9ebXgSsMM8%3D&reserved=0
> --
> Gaëtan Rivet
> 6WIND

Thanks 
Matan Azrad