linux-kernel - Re: [PATCH] rculist: fix sparse warning

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Date:	Fri, 12 Dec 2014 09:00:37 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Ying Xue <ying.xue@...driver.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rculist: fix sparse warning

On Fri, Dec 12, 2014 at 09:36:14AM +0800, Ying Xue wrote:
> This fixes the following sparse warning when using
> 
> make C=1 CF=-D__CHECK_ENDIAN__ net/ipv6/addrconf.o
> net/ipv6/addrconf.c:3495:9: error: incompatible types in comparison expression (different address spaces)
> net/ipv6/addrconf.c:3495:9: error: incompatible types in comparison expression (different address spaces)
> net/ipv6/addrconf.c:3495:9: error: incompatible types in comparison expression (different address spaces)
> net/ipv6/addrconf.c:3495:9: error: incompatible types in comparison expression (different address spaces)
> 
> To silence above spare complaint, an RCU annotation should be added to
> "next" pointer of hlist_node structure through hlist_next_rcu() macro
> when iterating over a hlist with hlist_for_each_entry_continue_rcu_bh().
> 
> By the way, this commit also resolves the same error appearing in
> hlist_for_each_entry_continue_rcu().
> 
> Signed-off-by: Ying Xue <ying.xue@...driver.com>

Queued for 3.20, thank you!

							Thanx, Paul

> ---
> The commit is based on next.2014.12.11a branch of linux-rcu tree 
> 
>  include/linux/rculist.h |   16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index 372ad5e..6f7aefb 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -524,11 +524,11 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
>   * @member:	the name of the hlist_node within the struct.
>   */
>  #define hlist_for_each_entry_continue_rcu(pos, member)			\
> -	for (pos = hlist_entry_safe(rcu_dereference((pos)->member.next),\
> -			typeof(*(pos)), member);			\
> +	for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
> +			&(pos)->member)), typeof(*(pos)), member);	\
>  	     pos;							\
> -	     pos = hlist_entry_safe(rcu_dereference((pos)->member.next),\
> -			typeof(*(pos)), member))
> +	     pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(	\
> +			&(pos)->member)), typeof(*(pos)), member))
> 
>  /**
>   * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point
> @@ -536,11 +536,11 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
>   * @member:	the name of the hlist_node within the struct.
>   */
>  #define hlist_for_each_entry_continue_rcu_bh(pos, member)		\
> -	for (pos = hlist_entry_safe(rcu_dereference_bh((pos)->member.next),\
> -			typeof(*(pos)), member);			\
> +	for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(  \
> +			&(pos)->member)), typeof(*(pos)), member);	\
>  	     pos;							\
> -	     pos = hlist_entry_safe(rcu_dereference_bh((pos)->member.next),\
> -			typeof(*(pos)), member))
> +	     pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(	\
> +			&(pos)->member)), typeof(*(pos)), member))
> 
> 
>  #endif	/* __KERNEL__ */
> -- 
> 1.7.9.5
> 

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