Re: [PATCH 1/2] ehea: fix delayed packet processing

From: Jay Vosburgh
Date: Tue Jun 15 2010 - 12:46:15 EST

Jan-Bernd Themann <ossthema@xxxxxxxxxx> 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@xxxxxxxxxx>

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.


Signed-off-by: Jay Vosburgh <fubar@xxxxxxxxxx>

>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);
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