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

[annie li <annie.li@oracle.com>]

On 2013-5-23 9:46, Wei Liu wrote:
> 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@oracle.com> wrote:
>>> On 2013-5-22 16:20, Wei Liu wrote:
>>>> On Wed, May 22, 2013 at 8:32 PM, annie li <annie.li@oracle.com> 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?

Yes, I think you are correct.

Thanks
Annie