netdev - Re: [PATCH v5 2/2] Ethernet driver for the WIZnet W5100 chip

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Date:	Fri, 30 Mar 2012 11:23:51 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Mike Sinkovsky <msink@...monline.ru>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] Ethernet driver for the WIZnet W5100 chip

Le vendredi 30 mars 2012 à 13:00 +0600, Mike Sinkovsky a écrit :
> Tested and used in production with Blackfin BF531 embedded processor.
> 
> Signed-off-by: Mike Sinkovsky <msink@...monline.ru>
> ---

> +
> +static int w5100_start_tx(struct sk_buff *skb, struct net_device *ndev)
> +{
> +	struct w5100_priv *priv = netdev_priv(ndev);
> +	u16 offset;
> +
> +	if (w5100_read16(priv, W5100_S0_TX_FSR) < skb->len) {

There is a race here.

Interrupt came come right here before you set the stop_queue()


> +		netif_stop_queue(ndev);

So Here I suggest adding a test again
	
	if (w5100_read16(priv, W5100_S0_TX_FSR) >= skb->len)
		netif_wake_queue(ndev);
	else
		return NETDEV_TX_BUSY;

> +		return NETDEV_TX_BUSY;
> +	}
> +
> +	offset = w5100_read16(priv, W5100_S0_TX_WR);
> +	w5100_writebuf(priv, offset, skb->data, skb->len);
> +	w5100_write16(priv, W5100_S0_TX_WR, offset + skb->len);
> +	w5100_command(priv, S0_CR_SEND);
> +	ndev->stats.tx_bytes += skb->len;
> +	ndev->stats.tx_packets++;
> +	dev_kfree_skb(skb);
> +
> +	return NETDEV_TX_OK;
> +}
> +



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