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From: Jay Vosburgh on 15 Jun 2010 12:50
Jan-Bernd Themann <ossthema(a)de.ibm.com> wrote:

>In the eHEA poll function an rmb() is required. Without that some packets
>on the receive queue are not seen and thus delayed until the next interrupt
>is handled for the same receive queue.
>
>Signed-off-by: Jan-Bernd Themann <themann(a)de.ibm.com>

To add a bit of background, this could manifest during a netperf
TCP_RR or UDP_RR on an otherwise idle network. TCP would occasionally
retransmit, but then both the original segment and the retransmission
would simultaneously appear at the receiver. For UDP_RR, message sizes
in excess of the mtu would occasionally "lose" an IP fragment, and
eventually IP reassembly would time out.

-J

Signed-off-by: Jay Vosburgh <fubar(a)us.ibm.com>


>---
>Patch created against 2.6.35-rc3
>
> drivers/net/ehea/ehea_main.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
>diff --git a/drivers/net/ehea/ehea_main.c b/drivers/net/ehea/ehea_main.c
>index f547894..fd890fa 100644
>--- a/drivers/net/ehea/ehea_main.c
>+++ b/drivers/net/ehea/ehea_main.c
>@@ -867,6 +867,7 @@ static int ehea_poll(struct napi_struct *napi, int budget)
> ehea_reset_cq_ep(pr->send_cq);
> ehea_reset_cq_n1(pr->recv_cq);
> ehea_reset_cq_n1(pr->send_cq);
>+ rmb();
> cqe = ehea_poll_rq1(pr->qp, &wqe_index);
> cqe_skb = ehea_poll_cq(pr->send_cq);
>
>--
>1.7.0
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From: David Miller on 16 Jun 2010 21:10
From: Jay Vosburgh <fubar(a)us.ibm.com>
Date: Tue, 15 Jun 2010 09:45:47 -0700

> Jan-Bernd Themann <ossthema(a)de.ibm.com> wrote:
>
>>In the eHEA poll function an rmb() is required. Without that some packets
>>on the receive queue are not seen and thus delayed until the next interrupt
>>is handled for the same receive queue.
>>
>>Signed-off-by: Jan-Bernd Themann <themann(a)de.ibm.com>
>
> To add a bit of background, this could manifest during a netperf
> TCP_RR or UDP_RR on an otherwise idle network. TCP would occasionally
> retransmit, but then both the original segment and the retransmission
> would simultaneously appear at the receiver. For UDP_RR, message sizes
> in excess of the mtu would occasionally "lose" an IP fragment, and
> eventually IP reassembly would time out.
>
> -J
>
> Signed-off-by: Jay Vosburgh <fubar(a)us.ibm.com>

Applied.
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