Re: [dpdk-stable] [dpdk-dev] [PATCH v1] net/tap: fix blocked rx packets error

["Smoczynski, MarcinX" <marcinx.smoczynski@intel.com>]

> -----Original Message-----
> From: Gavin Hu (Arm Technology China) [mailto:Gavin.Hu@arm.com]
> Sent: Thursday, September 5, 2019 7:44 AM
> To: Smoczynski, MarcinX <marcinx.smoczynski@intel.com>; Ananyev,
> Konstantin <konstantin.ananyev@intel.com>; Wiles, Keith
> <keith.wiles@intel.com>; adrien.mazarguil@6wind.com
> Cc: dev@dpdk.org; stable@dpdk.org; Drost, MariuszX
> <mariuszx.drost@intel.com>
> Subject: RE: [dpdk-dev] [PATCH v1] net/tap: fix blocked rx packets error
> 
> HI Marcin,
> 
> > -----Original Message-----
> > From: dev <dev-bounces@dpdk.org> On Behalf Of Marcin Smoczynski
> > Sent: Monday, September 2, 2019 7:43 PM
> > To: konstantin.ananyev@intel.com; keith.wiles@intel.com;
> > adrien.mazarguil@6wind.com
> > Cc: dev@dpdk.org; stable@dpdk.org; Marcin Smoczynski
> > <marcinx.smoczynski@intel.com>; Mariusz Drost
> > <mariuszx.drost@intel.com>
> > Subject: [dpdk-dev] [PATCH v1] net/tap: fix blocked rx packets error
> >
> > When OS sends more packets than are beaing read with a single
> s/ beaing/being

Thanks for that, will be corrected in the v2.

> 
> > 'rte_eth_rx_burst' call, rx packets are getting stucked in the tap pmd
> > and are unable to receive, because trigger_seen is getting updated and
> > consecutive calls are not getting any packets.
> >
> > Do not update trigger_seen unless less than a max number of packets
> > were received allowing next call to receive the rest.
> >
> > Fixes: a0d8e807d9 ("net/tap: add Rx trigger")
> > Cc: stable@dpdk.org
> >
> > Tested-by: Mariusz Drost <mariuszx.drost@intel.com>
> > Signed-off-by: Marcin Smoczynski <marcinx.smoczynski@intel.com>
> > ---
> >  drivers/net/tap/rte_eth_tap.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/tap/rte_eth_tap.c
> > b/drivers/net/tap/rte_eth_tap.c index 64bd04911..60121ae56 100644
> > --- a/drivers/net/tap/rte_eth_tap.c
> > +++ b/drivers/net/tap/rte_eth_tap.c
> > @@ -353,8 +353,7 @@ pmd_rx_burst(void *queue, struct rte_mbuf
> **bufs,
> > uint16_t nb_pkts)
> >
> >       if (trigger == rxq->trigger_seen)
> >               return 0;
> > -     if (trigger)
> > -             rxq->trigger_seen = trigger;
> > +
> >       process_private = rte_eth_devices[rxq->in_port].process_private;
> >       rte_compiler_barrier();
> I see this compiler barrier was added together with the above "rxq-
> >trigger_seen = trigger", should it be removed or moved together
> downwards?

I think it could be removed, but it is best to ask author of the original code.
Adrien, what do you think about removing this barrier?
 

> 
> >       for (num_rx = 0; num_rx < nb_pkts; ) { @@ -433,6 +432,9 @@
> > pmd_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> >       rxq->stats.ipackets += num_rx;
> >       rxq->stats.ibytes += num_rx_bytes;
> >
> > +     if (trigger && num_rx < nb_pkts)
> > +             rxq->trigger_seen = trigger;
> > +
> >       return num_rx;
> >  }
> >
> > --
> > 2.17.1
> 
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