From: Stephen Hemminger <stephen@networkplumber•org>
To: Haiyang Zhang <haiyangz@linuxonhyperv•com>
Cc: olaf@aepfle•de, sthemmin@microsoft•com, netdev@vger•kernel.org,
haiyangz@microsoft•com, linux-kernel@vger•kernel.org,
devel@linuxdriverproject•org, vkuznets@redhat•com,
davem@davemloft•net
Subject: Re: [PATCH net] hv_netvsc: Fix napi reschedule while receive completion is busy
Date: Mon, 9 Jul 2018 11:15:27 -0700 [thread overview]
Message-ID: <20180709111527.70ab354c@xeon-e3> (raw)
In-Reply-To: <20180709164319.5058-1-haiyangz@linuxonhyperv.com>
On Mon, 9 Jul 2018 16:43:19 +0000
Haiyang Zhang <haiyangz@linuxonhyperv•com> wrote:
> From: Haiyang Zhang <haiyangz@microsoft•com>
>
> If out ring is full temporarily and receive completion cannot go out,
> we may still need to reschedule napi if other conditions are met.
> Otherwise the napi poll might be stopped forever, and cause network
> disconnect.
>
> Fixes: 7426b1a51803 ("netvsc: optimize receive completions")
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft•com>
> ---
> drivers/net/hyperv/netvsc.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 8e9d0ee1572b..caaf5054f446 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -1285,14 +1285,14 @@ int netvsc_poll(struct napi_struct *napi, int budget)
> nvchan->desc = hv_pkt_iter_next(channel, nvchan->desc);
> }
>
> - /* If send of pending receive completions suceeded
> - * and did not exhaust NAPI budget this time
> + send_recv_completions(ndev, net_device, nvchan);
> +
> + /* If it did not exhaust NAPI budget this time
> * and not doing busy poll
> * then re-enable host interrupts
> * and reschedule if ring is not empty.
> */
> - if (send_recv_completions(ndev, net_device, nvchan) == 0 &&
> - work_done < budget &&
> + if (work_done < budget &&
> napi_complete_done(napi, work_done) &&
> hv_end_read(&channel->inbound) &&
> napi_schedule_prep(napi)) {
This patch doesn't look right. I think the existing code works
as written.
If send_receive_completions is unable to send because ring is full
then vmbus_sendpacket will return -EBUSY which gets returns
from send_receive_completions. Because the return is non-zero,
the driver will not call napi_complete_done.
Since napi_complete_done was not called, NAPI will reschedule
the napi poll routine.
next prev parent reply other threads:[~2018-07-09 18:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-09 16:43 [PATCH net] hv_netvsc: Fix napi reschedule while receive completion is busy Haiyang Zhang
2018-07-09 18:15 ` Stephen Hemminger [this message]
2018-07-09 18:33 ` Haiyang Zhang
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