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

[Gaëtan Rivet]

On Wed, Aug 16, 2017 at 09:02:31AM +0000, Matan Azrad wrote:
> Hi Gaetan
> 
> > -----Original Message-----
> > From: Gaëtan Rivet [mailto:gaetan.rivet at 6wind.com]
> > Sent: Wednesday, August 16, 2017 11:47 AM
> > To: Matan Azrad <matan at mellanox.com>
> > Cc: dev at dpdk.org; stable at 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.
> 	

Yes you're right, but the commit log should still be written in the
present tense:

  Remove the unreachable branch and add one in the right place respecting
  the original intent.

Or something like it :)

> > 
> > > 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 at mellanox.com>
> > > Cc: stable at 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 at 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

-- 
Gaëtan Rivet
6WIND