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

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Date:	Thu, 17 Jun 2010 14:03:19 +0200
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Cong Wang <amwang@...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 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.

> Why?

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

Stanislaw
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