netdev - Re: [PATCH] net: calxedaxgmac: Fix panic caused by MTU change of active interface

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Message-ID: <1383765756.1520.24.camel@bwh-desktop.uk.level5networks.com>
Date:	Wed, 6 Nov 2013 19:22:36 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Andreas Herrmann <andreas.herrmann@...xeda.com>
CC:	Rob Herring <rob.herring@...xeda.com>,
	Grant Likely <grant.likely@...aro.org>,
	"David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: calxedaxgmac: Fix panic caused by MTU change of
 active interface

On Wed, 2013-11-06 at 14:31 +0100, Andreas Herrmann wrote:
[...]
> diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
> index 48f5288..8eb422a 100644
> --- a/drivers/net/ethernet/calxeda/xgmac.c
> +++ b/drivers/net/ethernet/calxeda/xgmac.c
> @@ -1067,6 +1067,10 @@ static int xgmac_stop(struct net_device *dev)
>  
>  	writel(0, priv->base + XGMAC_DMA_INTR_ENA);
>  
> +	netif_tx_lock_bh(dev);
> +	netif_stop_queue(dev);
> +	netif_tx_unlock_bh(dev);
> +
[...]

There is already a call to netif_stop_queue() at the beginning of this
function, but without locking.  I think it's the wrong place because the
NAPI poller may still call netif_wake_queue() at that point.  You're
putting this in the *right* place, but I think you should remove the
first call.

Also this sequence is also equivalent to netif_tx_disable(), except that
that also works for multiqueue net devices.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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