linux-kernel - Re: [PATCH] net/hyperv: Fix the stop/wake queue mechanism

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Date:	Fri, 9 Dec 2011 08:35:08 -0800
From:	Greg KH <gregkh@...e.de>
To:	Haiyang Zhang <haiyangz@...rosoft.com>
Cc:	KY Srinivasan <kys@...rosoft.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
Subject: Re: [PATCH] net/hyperv: Fix the stop/wake queue mechanism

On Fri, Dec 09, 2011 at 04:00:59PM +0000, Haiyang Zhang wrote:
> > -----Original Message-----
> > From: Haiyang Zhang [mailto:haiyangz@...rosoft.com]
> > Sent: Friday, December 02, 2011 2:56 PM
> > To: Haiyang Zhang; KY Srinivasan; davem@...emloft.net; gregkh@...e.de;
> > linux-kernel@...r.kernel.org; netdev@...r.kernel.org;
> > devel@...uxdriverproject.org
> > Subject: [PATCH] net/hyperv: Fix the stop/wake queue mechanism
> > 
> > The ring buffer is only used to pass meta data for outbound packets. The
> > actual payload is accessed by DMA from the host. So the stop/wake queue
> > mechanism based on counting and comparing number of pages sent v.s.
> > number
> > of pages in the ring buffer is wrong. Also, there is a race condition in
> > the stop/wake queue calls, which can stop xmit queue forever.
> > 
> > The new stop/wake queue mechanism is based on the actual bytes used by
> > outbound packets in the ring buffer. The check for number of outstanding
> > sends after stop queue prevents the race condition that can cause wake
> > queue happening earlier than stop queue.
> > 
> > Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > Reported-by: Long Li <longli@...rosoft.com>
> > ---
> >  drivers/net/hyperv/netvsc.c     |   14 +++++++++++---
> >  drivers/net/hyperv/netvsc_drv.c |   24 +-----------------------
> >  2 files changed, 12 insertions(+), 26 deletions(-)
> 
> Hi Greg,
> 
> Since the netvsc haven't been merged into Dave's tree yet after out of staging,
> could you consider this patch for your tree?

It's in my "to-apply" queue already.

thanks,

greg k-h
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