lkml.org 
[lkml]   [2012]   [Mar]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 1/1] net/hyperv: Fix the code handling tx busy
Date


> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@gmail.com]
> Sent: Monday, March 19, 2012 1:12 PM
> To: Haiyang Zhang
> Cc: KY Srinivasan; davem@davemloft.net; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org
> Subject: Re: [PATCH 1/1] net/hyperv: Fix the code handling tx busy
>
> On Mon, 2012-03-19 at 10:02 -0700, Haiyang Zhang wrote:
> > Instead of dropping the packet, we keep the skb buffer, and return
> > NETDEV_TX_BUSY to let upper layer retry send. This will not cause
> > endless loop, because the host is taking data away from ring buffer.
> >
> > Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> > Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> > drivers/net/hyperv/netvsc_drv.c | 5 +----
> > 1 files changed, 1 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/netvsc_drv.c
> > b/drivers/net/hyperv/netvsc_drv.c index 2517d20..dd29478 100644
> > --- a/drivers/net/hyperv/netvsc_drv.c
> > +++ b/drivers/net/hyperv/netvsc_drv.c
> > @@ -223,13 +223,10 @@ static int netvsc_start_xmit(struct sk_buff *skb,
> struct net_device *net)
> > net->stats.tx_bytes += skb->len;
> > net->stats.tx_packets++;
> > } else {
> > - /* we are shutting down or bus overloaded, just drop packet
> */
> > - net->stats.tx_dropped++;
> > kfree(packet);
> > - dev_kfree_skb_any(skb);
> > }
> >
> > - return NETDEV_TX_OK;
> > + return ret ? NETDEV_TX_BUSY : NETDEV_TX_OK;
> > }
> >
> > /*
>
> Thats simply not true at all.
>
> A start_xmit() cannot do that.
>
> TX_BUSY should never be returned at all, its a deprecated code, for pretty
> good reasons. (assuming queue is not stopped)

We actually stop queue when the ring buffer is busy, see the code in netvsc.c

> Try this on a machine with one CPU, I am pretty sure this can trigger
> complete freezes.

I have tested with one CPU. After NETDEV_TX_BUSY is returned, the Linux
guest OS continues to respond without any problem.

Thanks,
- Haiyang

\
 
 \ /
  Last update: 2012-03-19 18:49    [from the cache]
©2003-2011 Jasper Spaans