linux-kernel - Re: [PATCH v2 3/7] [PATCH 3/8] can: CAN Network device driver and Netlink interface

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Message-ID: <20090513153112.0822809b@bike.lwn.net>
Date:	Wed, 13 May 2009 15:31:12 -0600
From:	Jonathan Corbet <corbet@....net>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wolfgang Grandegger <wg@...ndegger.com>,
	Oliver Hartkopp <oliver.hartkopp@...kswagen.de>
Subject: Re: [PATCH v2 3/7] [PATCH 3/8] can: CAN Network device driver and
 Netlink interface

[Quick review ...]

> +/*
> + * CAN device restart for bus-off recovery
> + */
> +int can_restart_now(struct net_device *dev)
> +{
> +	struct can_priv *priv = netdev_priv(dev);
> +	struct net_device_stats *stats = &dev->stats;
> +	struct sk_buff *skb;
> +	struct can_frame *cf;
> +	int err;
> +
> +	/* Synchronize with dev->hard_start_xmit() */
> +	netif_tx_lock(dev);
> +
> +	/* Ensure that no more messages can go out */
> +	if (netif_carrier_ok(dev))
> +		netif_carrier_off(dev);
> +
> +	/* Ensure that no more messages can come in */
> +	err = priv->do_set_mode(dev, CAN_MODE_STOP);
> +	if (err)
> +		return err;

This leaves _xmit_lock held and carrier off.  Is that really what you want
to do?

> +
> +	/*  Now it's save to clean up */
> +	del_timer_sync(&priv->restart_timer);
> +	can_flush_echo_skb(dev);
> +
> +	dev_dbg(dev->dev.parent, "restarted\n");
> +	priv->can_stats.restarts++;
> +
> +	/* send restart message upstream */
> +	skb = dev_alloc_skb(sizeof(struct can_frame));
> +	if (skb == NULL)
> +		return -ENOMEM;

...here too...

> +	skb->dev = dev;
> +	skb->protocol = htons(ETH_P_CAN);
> +	cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
> +	memset(cf, 0, sizeof(struct can_frame));
> +	cf->can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED;
> +	cf->can_dlc = CAN_ERR_DLC;
> +
> +	netif_rx(skb);
> +
> +	dev->last_rx = jiffies;
> +	stats->rx_packets++;
> +	stats->rx_bytes += cf->can_dlc;
> +
> +	/* Now restart the device */
> +	err = priv->do_set_mode(dev, CAN_MODE_START);
> +	if (err)
> +		return err;

...and here too.  Do you maybe want to get rid of the middle-of-function
returns and switch to the "goto out" convention?

> +	netif_carrier_on(dev);
> +
> +	netif_tx_unlock(dev);
> +
> +	return 0;
> +}
> +
> +static void can_restart_after(unsigned long data)
> +{
> +	struct net_device *dev = (struct net_device *)data;
> +
> +	can_restart_now(dev);
> +}

can_restart_after what?  I find myself confused by this function and
wondering why it exists.

jon
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