[dpdk-dev] [PATCH v2] kni: fix kni Rx fifo producer synchronization

[Kokkilagadda, Kiran]

In this instance there won't be any problem, as until the value of fifo->write changes, this loop won't get executed. As of now we didn't see any issue with it and for performance reasons, we don't want to keep read barrier.



________________________________
From: Gavin Hu <Gavin.Hu at arm.com>
Sent: Monday, August 27, 2018 9:10 PM
To: Ferruh Yigit; Kokkilagadda, Kiran; Jacob, Jerin
Cc: dev at dpdk.org; Honnappa Nagarahalli
Subject: RE: [dpdk-dev] [PATCH v2] kni: fix kni Rx fifo producer synchronization

External Email

This fix is not complete, kni_fifo_get requires a read fence also, otherwise it probably gets stale data on a weak ordering platform.

> -----Original Message-----
> From: dev <dev-bounces at dpdk.org> On Behalf Of Ferruh Yigit
> Sent: Monday, August 27, 2018 10:08 PM
> To: Kiran Kumar <kkokkilagadda at caviumnetworks.com>;
> jerin.jacob at caviumnetworks.com
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2] kni: fix kni Rx fifo producer
> synchronization
>
> On 8/16/2018 10:55 AM, Kiran Kumar wrote:
> > With existing code in kni_fifo_put, rx_q values are not being updated
> > before updating fifo_write. While reading rx_q in kni_net_rx_normal,
> > This is causing the sync issue on other core. So adding a write
> > barrier to make sure the values being synced before updating fifo_write.
> >
> > Fixes: 3fc5ca2f6352 ("kni: initial import")
> >
> > Signed-off-by: Kiran Kumar <kkokkilagadda at caviumnetworks.com>
> > Acked-by: Jerin Jacob <jerin.jacob at caviumnetworks.com>
>
> Acked-by: Ferruh Yigit <ferruh.yigit at intel.com>
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