Messages in this thread | | | Subject | Re: [net-next PATCH 1/5] net: Do not record sender_cpu as napi_id in socket receive paths | From | Eric Dumazet <> | Date | Thu, 16 Mar 2017 15:05:36 -0700 |
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On Thu, 2017-03-16 at 11:32 -0700, Alexander Duyck wrote: > From: Sridhar Samudrala <sridhar.samudrala@intel.com> > > Fix sk_mark_napi_id() and sk_mark_napi_id_once() to set sk_napi_id only if > skb->napi_id is a valid value. > > This happens in loopback paths where skb->napi_id is not updated in > rx path and holds sender_cpu that is set in xmit path. > > Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com> > Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> > --- > include/net/busy_poll.h | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h > index c0452de83086..67991635953e 100644 > --- a/include/net/busy_poll.h > +++ b/include/net/busy_poll.h > @@ -116,7 +116,8 @@ static inline bool sk_busy_loop(struct sock *sk, int nonblock) > static inline void sk_mark_napi_id(struct sock *sk, const struct sk_buff *skb) > { > #ifdef CONFIG_NET_RX_BUSY_POLL > - sk->sk_napi_id = skb->napi_id; > + if (skb->napi_id > (u32)NR_CPUS) > + sk->sk_napi_id = skb->napi_id; > #endif > } > > @@ -125,7 +126,7 @@ static inline void sk_mark_napi_id_once(struct sock *sk, > const struct sk_buff *skb) > { > #ifdef CONFIG_NET_RX_BUSY_POLL > - if (!sk->sk_napi_id) > + if (!sk->sk_napi_id && (skb->napi_id > (u32)NR_CPUS)) > sk->sk_napi_id = skb->napi_id; > #endif > } >
It is not clear why this patch is needed .
What you describe here is the case we might receive packets for a socket coming from different interfaces ?
If skb->napi_id is a sender_cpu, why should we prevent overwriting the sk_napi_id with it, knowing that busy polling will simply ignore the invalid value ?
Do not get me wrong :
I simply try to understand why the test about napi_id validity is now done twice :
1) At the time we are writing into sk->sk_napi_id
2) At busy polling time when we read sk->sk_napi_id
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