Re: [Xen-devel] [PATCH net-next V3 2/3] xen-netfront: split event channels support for Xen frontend driver

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, May 22, 2013 at 09:38:20PM +0100, Wei Liu wrote:
> On Wed, May 22, 2013 at 9:35 PM, annie li <annie.li@xxxxxxxxxx> wrote:
> >
> > On 2013-5-22 16:20, Wei Liu wrote:
> >>
> >> On Wed, May 22, 2013 at 8:32 PM, annie li <annie.li@xxxxxxxxxx> wrote:
> >>>
> >>>
> >>> Originally, netfront protects access to rx shared-ring with tx_lock, you
> >>> remove this protection here. It is better to protect the ring access by a
> >>> sperate rx_lock then.
> >>>
> >> TX ring and RX ring are separate rings. I don't think that comment / code
> >> makes sense any more. My stress test confirms that.
> >
> >
> > Yes, they are separate rings. Actually I am not sure why
> > RING_HAS_UNCONSUMED_RESPONSES(&np->rx) is protected by any tx_lock
> > originally. But for xennet_rx_interrupt, it is better to use rx_lock to
> > protect RING_HAS_UNCONSUMED_RESPONSES(&np->rx).
> >
> 
> This doesn't make sense to me either. Xen ring protocol is designed to
> be lock-free.
> And in netfront's case there is no concurrent access to the ring.
> 
> 

Annie, did I answer your questions / relieve your concern?


Wei.

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