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

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Message-ID: <20100615113926.30d0cd01@dhcp-lab-109.englab.brq.redhat.com>
Date:	Tue, 15 Jun 2010 11:39:26 +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 Tue, 15 Jun 2010 16:53:27 +0800
Cong Wang <amwang@...hat.com> wrote:

> > If so, it's better to stop device before modify LRO settings. I suggest
> > something like that in mlx4_ethtool_op_set_flags:
> >
> > if (!!(data&  ETH_FLAG_LRO) != !!(dev->features&  NETIF_F_LRO)) {
>
> What does this line mean? This is to ignore all other flags, right?

Yes, plus check if we are really changing current settings.
 
> > 	/* Need to toggle LRO */
> >
> > 	if (netdev_running(dev)) {
> >                 mutex_lock(&mdev->state_lock);
> >                 mlx4_en_stop_port(dev);
> >                 rc = mlx4_en_start_port(dev);
> >                 if (rc)
> >                         en_err(priv, "Failed to restart port\n");
> > 	}
> >
> > 	dev->features ^= NETIF_F_LRO;
> >
> > 	if (netdev_running(dev))
> >                 mutex_unlock(&mdev->state_lock);
> > }
> >
> 
> 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");
	}

Stanislaw
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