[dpdk-dev] [PATCH] ethdev: fix wrong memset

[Yuanhan Liu]

On Mon, Jan 23, 2017 at 07:40:50PM +0800, Yuanhan Liu wrote:
> On Mon, Jan 23, 2017 at 11:32:23AM +0000, Ferruh Yigit wrote:
> > On 1/23/2017 11:24 AM, Yuanhan Liu wrote:
> > > On Mon, Jan 23, 2017 at 11:05:25AM +0000, Ferruh Yigit wrote:
> > >>>>>>>>  lib/librte_ether/rte_ethdev.c | 2 +-
> > >>>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> > >>>>>>>>
> > >>>>>>>> diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
> > >>>>>>>> index 4790faf..61f44e2 100644
> > >>>>>>>> --- a/lib/librte_ether/rte_ethdev.c
> > >>>>>>>> +++ b/lib/librte_ether/rte_ethdev.c
> > >>>>>>>> @@ -225,7 +225,7 @@ struct rte_eth_dev *
> > >>>>>>>>  		return NULL;
> > >>>>>>>>  	}
> > >>>>>>>>  
> > >>>>>>>> -	memset(&rte_eth_devices[port_id], 0, sizeof(*eth_dev->data));
> > >>>>>>>> +	memset(&rte_eth_dev_data[port_id], 0, sizeof(struct rte_eth_dev_data));
> > >>>>>>>
> > >>>>>>> Not directly related to the this issue, but, after fix, this may have
> > >>>>>>> issues with secondary process.
> > >>>>>>>
> > >>>>>>> There were patches sent to fix this.
> > >>>>>>
> > >>>>>> I mean this one:
> > >>>>>> http://dpdk.org/ml/archives/dev/2017-January/054422.html
> > >>>>>
> > >>>>> d948f596fee2 ("ethdev: fix port data mismatched in multiple process
> > >>>>> model") should have fixed it.
> > >>>>
> > >>>> Think about case, where secondary process uses a virtual PMD, which does
> > >>>> a rte_eth_dev_allocate() call, shouldn't this corrupt primary process
> > >>>> device data?
> > >>>
> > >>> Yes, it may. However, I doubt that's the typical usage. 
> > >>
> > >> But this is a use case, and broken now,
> > > 
> > > I thought it was broken since the beginning?
> > 
> > No, memset(&rte_eth_dev_data[port_id], ...) breaks it.
> 
> Oh, you were talking about that particular case Remy's patch meant to
> fix.
> 
> > >> and fix is known.
> > > 
> > > And there is already a fix?
> > 
> > http://dpdk.org/ml/archives/dev/2017-January/054422.html
> 
> Yes, it should fix that issue.

Well, few more thoughts: it may fix the crash issue Remy saw, but it
looks like more a workaround to me. Basically, if primary and secondary
shares a same port id, they should point to same device. Otherwise,
primary process may use eth_dev->data for a device A, while the
secondary process may use it for another device, as you said, it
could be a vdev.

In such case, there is no way we could continue safely. That said,
the given patch avoids the total reset of eth_dev->data, while it
continues reset the eth_dev->data->name, which is wrong.

So it's not a proper fix.

Again, I think it's more about the usage. If primary starts with
a nic device A, while the secondary starts with a nic device B,
there is no way they could work well (unless they use different
port id).

	--yliu

> One question: do Remy or you regularly
> run some multiple process test cases (and with vdev both in primary
> and secondary process)?