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SubjectRe: [PATCH] rculist: Fix another sparse warning
On Wed, Mar 25, 2015 at 12:43:38PM +0800, Ying Xue wrote:
> This fixes the following sparse warnings:
>
> make C=1 CF=-D__CHECK_ENDIAN__ net/tipc/name_table.o
> net/tipc/name_table.c:977:17: error: incompatible types in comparison expression (different address spaces)
> net/tipc/name_table.c:977:17: error: incompatible types in comparison expression (different address spaces)
>
> To silence these spare complaints, 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_from_rcu().
>
> Signed-off-by: Ying Xue <ying.xue@windriver.com>

If hlist_for_each_entry_from_rcu() is to use rcu_dereference_bh(), then
it needs to be named hlist_for_each_entry_from_rcu_bh(). If we want
to retain the generic nature, rcu_dereference_raw() would work.

(Otherwise, we would get splats if this was used under rcu_read_lock()
rather than rcu_read_lock_bh().)

Thanx, Paul

> ---
> include/linux/rculist.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index a18b16f..18a3f15 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -549,8 +549,8 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
> */
> #define hlist_for_each_entry_from_rcu(pos, member) \
> for (; pos; \
> - pos = hlist_entry_safe(rcu_dereference((pos)->member.next),\
> - typeof(*(pos)), member))
> + pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \
> + &(pos)->member)), typeof(*(pos)), member))
>
> #endif /* __KERNEL__ */
> #endif
> --
> 1.7.9.5
>



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