netdev - Re: br_forward.c - rcu dereference warning

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Message-ID: <1280261679.3755.6.camel@jlt3.sipsolutions.net>
Date:	Tue, 27 Jul 2010 22:14:39 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	paulmck@...ux.vnet.ibm.com, netdev <netdev@...r.kernel.org>
Subject: Re: br_forward.c - rcu dereference warning

On Tue, 2010-07-27 at 11:26 -0700, Stephen Hemminger wrote:

> -/* net device transmit always called with no BH (preempt_disabled) */
> +/* net device transmit always called with no BH disabled */

"no BH disabled"?

> @@ -48,6 +48,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *
>  	skb_reset_mac_header(skb);
>  	skb_pull(skb, ETH_HLEN);
>  
> +	rcu_read_lock();
>  	if (is_multicast_ether_addr(dest)) {
>  		if (unlikely(netpoll_tx_running(dev))) {
>  			br_flood_deliver(br, skb);
> @@ -67,6 +68,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *
>  		br_flood_deliver(br, skb);
>  
>  out:
> +	rcu_read_unlock();
>  	return NETDEV_TX_OK;
>  }
>  
> --- a/net/bridge/br_fdb.c	2010-07-27 11:18:30.815320981 -0700
> +++ b/net/bridge/br_fdb.c	2010-07-27 11:18:59.597710975 -0700
> @@ -214,7 +214,7 @@ void br_fdb_delete_by_port(struct net_br
>  	spin_unlock_bh(&br->hash_lock);
>  }
>  
> -/* No locking or refcounting, assumes caller has no preempt (rcu_read_lock) */
> +/* No locking or refcounting, assumes caller has rcu_read_lock */
>  struct net_bridge_fdb_entry *__br_fdb_get(struct net_bridge *br,
>  					  const unsigned char *addr)
>  {
> --- a/net/bridge/br_input.c	2010-07-27 11:19:05.266181492 -0700
> +++ b/net/bridge/br_input.c	2010-07-27 11:19:29.148163149 -0700
> @@ -39,7 +39,7 @@ static int br_pass_frame_up(struct sk_bu
>  		       netif_receive_skb);
>  }
>  
> -/* note: already called with rcu_read_lock (preempt_disabled) */
> +/* note: already called with rcu_read_lock */
>  int br_handle_frame_finish(struct sk_buff *skb)
>  {
>  	const unsigned char *dest = eth_hdr(skb)->h_dest;
> @@ -110,7 +110,7 @@ drop:
>  	goto out;
>  }
>  
> -/* note: already called with rcu_read_lock (preempt_disabled) */
> +/* note: already called with rcu_read_lock */
>  static int br_handle_local_finish(struct sk_buff *skb)
>  {
>  	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
> @@ -133,8 +133,7 @@ static inline int is_link_local(const un
>  
>  /*
>   * Return NULL if skb is handled
> - * note: already called with rcu_read_lock (preempt_disabled) from
> - * netif_receive_skb
> + * note: already called with rcu_read_lock from netif_receive_skb
>   */
>  struct sk_buff *br_handle_frame(struct sk_buff *skb)
>  {
> --- a/net/bridge/br_stp_bpdu.c	2010-07-27 11:19:34.092573294 -0700
> +++ b/net/bridge/br_stp_bpdu.c	2010-07-27 11:19:40.725123403 -0700
> @@ -131,7 +131,7 @@ void br_send_tcn_bpdu(struct net_bridge_
>  /*
>   * Called from llc.
>   *
> - * NO locks, but rcu_read_lock (preempt_disabled)
> + * NO locks, but rcu_read_lock
>   */
>  void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
>  		struct net_device *dev)
> 

Did you want me to test the patch?

johannes

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