netdev - Re: [Patch 2/2] mlx4: add dynamic LRO disable support

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Date:	Fri, 18 Jun 2010 11:10:31 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
CC:	Ben Hutchings <bhutchings@...arflare.com>, netdev@...r.kernel.org,
	herbert.xu@...hat.com, nhorman@...hat.com, davem@...emloft.net
Subject: Re: [Patch 2/2] mlx4: add dynamic LRO disable support

On 06/17/10 20:03, Stanislaw Gruszka wrote:
> On Thu, Jun 17, 2010 at 06:54:28PM +0800, Cong Wang wrote:
>>>> I don't think mdev->state_lock is used to protect dev->feature.
>>>> rtnl_lock is. I think switching to mlx4_ethtool_op_set_flags()
>>>> from the default one has already solved this.
>>>
>>> Ahh, you have right, may intention was use it to stop and start
>>> port. Code rather should look like below:
>>>
>>> 	if (netdev_running(dev)) {
>>> 		mutex_lock(&mdev->state_lock);
>>> 		mlx4_en_stop_port(dev);
>>> 	}
>>>
>>> 	dev->features ^= NETIF_F_LRO;
>>>
>>> 	if (netdev_running(dev)) {
>>> 		rc = mlx4_en_start_port(dev);
>>> 		mutex_unlock(&mdev->state_lock);
>>>    		if (rc)
>>> 		en_err(priv, "Failed to restart port\n");
>>> 	}
>>>
>>
>> Hmm, you mean ->features should be changed after port is stopped?
>
> Actually not ->features variable, but NETIF_F_LRO bit, as only this
> bit is used in rx path.
>

Yeah, this is what I meant.

>> Why?
>
> For reasons you talked before in this thread :) to do not change
> LRO in the middle of receiving packages.
>

Ohh... I missed this, seems reasonable, will fix this in the next update.

Thanks.
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