Subject: Re: [PATCH net-next-2.6] net: if6_get_next() fix

From: "Paul E. McKenney" <[email-masked]>
Date: Mon, 3 May 2010 15:52:29 -0700

On Mon, May 03, 2010 at 10:50:14PM +0200, Eric Dumazet wrote:
> Paul, David, here the patch I was thinking about :
> 
> Feel free to split it in two parts if you like, I am too tired and must
> sleep now ;)
> 
> Thanks
> 
> [PATCH net-next-2.6] net: rcu fixes
> 
> Add hlist_for_each_entry_rcu_bh() and
> hlist_for_each_entry_continue_rcu_bh() macros, and use them in
> ipv6_get_ifaddr(), if6_get_first() and if6_get_next() to fix lockdeps
> warnings.

Looks good!!!

It will collide with Arnd's sparse-based changes, but that will be
easy to fix, so no problem.

Reviewed-by: "Paul E. McKenney" <[email-masked]>

> Signed-off-by: Eric Dumazet <[email-masked]>
> ---
>  include/linux/rculist.h |   29 +++++++++++++++++++++++++++++
>  net/ipv6/addrconf.c     |   16 ++++++++--------
>  2 files changed, 37 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index 004908b..4ec3b38 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -429,6 +429,23 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
>  		pos = rcu_dereference_raw(pos->next))
> 
>  /**
> + * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type
> + * @tpos:	the type * to use as a loop cursor.
> + * @pos:	the &struct hlist_node to use as a loop cursor.
> + * @head:	the head for your list.
> + * @member:	the name of the hlist_node within the struct.
> + *
> + * This list-traversal primitive may safely run concurrently with
> + * the _rcu list-mutation primitives such as hlist_add_head_rcu()
> + * as long as the traversal is guarded by rcu_read_lock().
> + */
> +#define hlist_for_each_entry_rcu_bh(tpos, pos, head, member)		 \
> +	for (pos = rcu_dereference_bh((head)->first);			 \
> +		pos && ({ prefetch(pos->next); 1; }) &&			 \
> +		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
> +		pos = rcu_dereference_bh(pos->next))
> +
> +/**
>   * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point
>   * @tpos:	the type * to use as a loop cursor.
>   * @pos:	the &struct hlist_node to use as a loop cursor.
> @@ -440,6 +457,18 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
>  	     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; });  \
>  	     pos = rcu_dereference(pos->next))
> 
> +/**
> + * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point
> + * @tpos:	the type * to use as a loop cursor.
> + * @pos:	the &struct hlist_node to use as a loop cursor.
> + * @member:	the name of the hlist_node within the struct.
> + */
> +#define hlist_for_each_entry_continue_rcu_bh(tpos, pos, member)		\
> +	for (pos = rcu_dereference_bh((pos)->next);			\
> +	     pos && ({ prefetch(pos->next); 1; }) &&			\
> +	     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; });  \
> +	     pos = rcu_dereference_bh(pos->next))
> +
> 
>  #endif	/* __KERNEL__ */
>  #endif
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 34d2d64..3984f52 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -1346,7 +1346,7 @@ struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, const struct in6_addr *add
>  	struct hlist_node *node;
> 
>  	rcu_read_lock_bh();
> -	hlist_for_each_entry_rcu(ifp, node, &inet6_addr_lst[hash], addr_lst) {
> +	hlist_for_each_entry_rcu_bh(ifp, node, &inet6_addr_lst[hash], addr_lst) {
>  		if (!net_eq(dev_net(ifp->idev->dev), net))
>  			continue;
>  		if (ipv6_addr_equal(&ifp->addr, addr)) {
> @@ -2959,7 +2959,7 @@ static struct inet6_ifaddr *if6_get_first(struct seq_file *seq)
> 
>  	for (state->bucket = 0; state->bucket < IN6_ADDR_HSIZE; ++state->bucket) {
>  		struct hlist_node *n;
> -		hlist_for_each_entry_rcu(ifa, n, &inet6_addr_lst[state->bucket],
> +		hlist_for_each_entry_rcu_bh(ifa, n, &inet6_addr_lst[state->bucket],
>  					 addr_lst)
>  			if (net_eq(dev_net(ifa->idev->dev), net))
>  				return ifa;
> @@ -2974,12 +2974,12 @@ static struct inet6_ifaddr *if6_get_next(struct seq_file *seq,
>  	struct net *net = seq_file_net(seq);
>  	struct hlist_node *n = &ifa->addr_lst;
> 
> -	hlist_for_each_entry_continue_rcu(ifa, n, addr_lst)
> +	hlist_for_each_entry_continue_rcu_bh(ifa, n, addr_lst)
>  		if (net_eq(dev_net(ifa->idev->dev), net))
>  			return ifa;
> 
>  	while (++state->bucket < IN6_ADDR_HSIZE) {
> -		hlist_for_each_entry(ifa, n,
> +		hlist_for_each_entry_rcu_bh(ifa, n,
>  				     &inet6_addr_lst[state->bucket], addr_lst) {
>  			if (net_eq(dev_net(ifa->idev->dev), net))
>  				return ifa;
> @@ -3000,7 +3000,7 @@ static struct inet6_ifaddr *if6_get_idx(struct seq_file *seq, loff_t pos)
>  }
> 
>  static void *if6_seq_start(struct seq_file *seq, loff_t *pos)
> -	__acquires(rcu)
> +	__acquires(rcu_bh)
>  {
>  	rcu_read_lock_bh();
>  	return if6_get_idx(seq, *pos);
> @@ -3016,7 +3016,7 @@ static void *if6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
>  }
> 
>  static void if6_seq_stop(struct seq_file *seq, void *v)
> -	__releases(rcu)
> +	__releases(rcu_bh)
>  {
>  	rcu_read_unlock_bh();
>  }
> @@ -3093,7 +3093,7 @@ int ipv6_chk_home_addr(struct net *net, struct in6_addr *addr)
>  	unsigned int hash = ipv6_addr_hash(addr);
> 
>  	rcu_read_lock_bh();
> -	hlist_for_each_entry_rcu(ifp, n, &inet6_addr_lst[hash], addr_lst) {
> +	hlist_for_each_entry_rcu_bh(ifp, n, &inet6_addr_lst[hash], addr_lst) {
>  		if (!net_eq(dev_net(ifp->idev->dev), net))
>  			continue;
>  		if (ipv6_addr_equal(&ifp->addr, addr) &&
> @@ -3127,7 +3127,7 @@ static void addrconf_verify(unsigned long foo)
> 
>  	for (i = 0; i < IN6_ADDR_HSIZE; i++) {
>  restart:
> -		hlist_for_each_entry_rcu(ifp, node,
> +		hlist_for_each_entry_rcu_bh(ifp, node,
>  					 &inet6_addr_lst[i], addr_lst) {
>  			unsigned long age;
> 
> 
> 
> --
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