Subject: Re: [PATCH] Found skb leak in mpc5200 fec on rxfifo error

From: "Asier Llano Palacios" <[email-masked]>
Date: Fri, 16 Oct 2009 18:10:19 +0200

Sorry, but it seems that the patch did already do the work. The other
problems were hardware problems and are not related to this patch (it
even happened without applying it). So it seems that the skb leak may be
solved with the provided patch.

Kind regards,
Asier

El vie, 16-10-2009 a las 14:01 +0200, Asier Llano Palacios escribió:
> (I'm sorry about my previous message with a legal notice, this time
> I resent it with another mail server that doesn't include the legal
> notice for me)
> 
> Hi all,
> 
> I finally found why in my mpc5200 based system (and in the lite5200) I
> had leaks of skbs when receiving ethernet traffic at 100 Mbit/s so that
> we generated an rxfifo error (to be able to get it I even reduced the
> speed of the CPU using the PLL jumpers).
> 
> The problem was:
> 
> The reception packets are handled in the interrupt handler:
> mpc52xx_fec_rx_interrupt. So this interrupt is being handled all the
> time because we are receiving packets continuously.
> 
> The reception fifo errors are handled in the interrupt handler:
> mpc52xx_fec_interrupt. This interruption is being handled very often
> because we are receiving more packets that what we can handle, and that
> generates a fifo reception error.
> 
> So it is very usual that the mpc52xx_fec_interrupt handler is executed
> at the middle of the mpc52xx_fec_rx_interrupt handler. And I think that
> it is not designed for that purpose.
> 
> The mpc52xx_fec_rx_interrupt uses bcom_retrieve_buffer and
> bcom_submit_next_buffer. The mpc52xx_fec_interrupt calls to
> mpc52xx_fec_reset which calls to mpc52xx_fec_free_rx_buffers and
> mpc52xx_fec_alloc_rx_buffers, which at the end call bcom_retrieve_buffer
> and bcom_submit_next_buffer.
> 
> Then we have two problems because of the same origin:
>  - bcom_retrieve_buffer and bcom_submit_next_buffer doesn't seem to be
>    atomic, so they cannot be called from one interrupt nested from
>    another one being executing those functions.
>  - Even if they were atomic, the mpc52xx_fec_rx_interrupt and the
>    mpc52xx_fec_reset functions are not intended to be called at the
>    same time.
> 
> Patch I managed to do:
>  I've managed to perform a patch that avoids the leak disabling the
>  irqs, but I have a remaining problem: The last  packet to be transmited
>  is waiting for a packet to be received in order to egress (I don't know
>  why but I detected it experimentaly).
>  
> Anyone with more experience can tell me what's wrong in this patch?
> 
> Thank you in advance,
> Asier
> 
> Signed-off-by: Asier Llano <[email-masked]>
> ---
>  drivers/net/fec_mpc52xx.c |   23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff -urpN linux-2.6.31.2/drivers/net/fec_mpc52xx.c
> linux-2.6.31.2-fec_mpc52xx_skb_leak/drivers/net/fec_mpc52xx.c
> ================================================================
> --- linux-2.6.31.2/drivers/net/fec_mpc52xx.c
> +++ linux-2.6.31.2-fec_mpc52xx_skb_leak/drivers/net/fec_mpc52xx.c
> @@ -85,13 +85,20 @@ MODULE_PARM_DESC(debug, "debugging messa
>  
>  static void mpc52xx_fec_tx_timeout(struct net_device *dev)
>  {
> +	struct mpc52xx_fec_priv *priv = netdev_priv(dev);
> +	unsigned long flags;
> +
>  	dev_warn(&dev->dev, "transmit timed out\n");
>  
> +	spin_lock_irqsave(&priv->lock, flags);
> +
>  	mpc52xx_fec_reset(dev);
>  
>  	dev->stats.tx_errors++;
>  
>  	netif_wake_queue(dev);
> +
> +	spin_unlock_irqrestore(&priv->lock, flags);
>  }
>  
>  static void mpc52xx_fec_set_paddr(struct net_device *dev, u8 *mac)
> @@ -359,8 +366,9 @@ static irqreturn_t mpc52xx_fec_tx_interr
>  {
>  	struct net_device *dev = dev_id;
>  	struct mpc52xx_fec_priv *priv = netdev_priv(dev);
> +	unsigned long flags;
>  
> -	spin_lock(&priv->lock);
> +	spin_lock_irqsave(&priv->lock, flags);
>  
>  	while (bcom_buffer_done(priv->tx_dmatsk)) {
>  		struct sk_buff *skb;
> @@ -375,7 +383,7 @@ static irqreturn_t mpc52xx_fec_tx_interr
>  
>  	netif_wake_queue(dev);
>  
> -	spin_unlock(&priv->lock);
> +	spin_unlock_irqrestore(&priv->lock, flags);
>  
>  	return IRQ_HANDLED;
>  }
> @@ -384,6 +392,9 @@ static irqreturn_t mpc52xx_fec_rx_interr
>  {
>  	struct net_device *dev = dev_id;
>  	struct mpc52xx_fec_priv *priv = netdev_priv(dev);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&priv->lock, flags);
>  
>  	while (bcom_buffer_done(priv->rx_dmatsk)) {
>  		struct sk_buff *skb;
> @@ -445,6 +456,8 @@ static irqreturn_t mpc52xx_fec_rx_interr
>  		bcom_submit_next_buffer(priv->rx_dmatsk, skb);
>  	}
>  
> +	spin_unlock_irqrestore(&priv->lock, flags);
> +
>  	return IRQ_HANDLED;
>  }
>  
> @@ -454,6 +467,7 @@ static irqreturn_t mpc52xx_fec_interrupt
>  	struct mpc52xx_fec_priv *priv = netdev_priv(dev);
>  	struct mpc52xx_fec __iomem *fec = priv->fec;
>  	u32 ievent;
> +	unsigned long flags;
>  
>  	ievent = in_be32(&fec->ievent);
>  
> @@ -471,9 +485,14 @@ static irqreturn_t mpc52xx_fec_interrupt
>  		if (net_ratelimit() && (ievent & FEC_IEVENT_XFIFO_ERROR))
>  			dev_warn(&dev->dev, "FEC_IEVENT_XFIFO_ERROR\n");
>  
> +		spin_lock_irqsave(&priv->lock, flags);
> +
>  		mpc52xx_fec_reset(dev);
>  
>  		netif_wake_queue(dev);
> +
> +		spin_unlock_irqrestore(&priv->lock, flags);
> +
>  		return IRQ_HANDLED;
>  	}
>  
> 
> 
> _______________________________________________
> Linuxppc-dev mailing list
> [email-masked]
> https://lists.ozlabs.org/listinfo/linuxppc-dev 
 
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