[PATCH net-next] ipv6: fix sparse warning

[PATCH net-next] ipv6: fix sparse warning

[Ying Xue]

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@windriver.com>
---
 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 866d9c9..32bd4ad 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))
 
 /**
  * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point
-- 
1.7.9.5

Re: [PATCH net-next] ipv6: fix sparse warning

[David Miller]

From: Ying Xue <ying.xue@windriver.com>
Date: Wed, 10 Dec 2014 11:28:21 +0800

> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index 866d9c9..32bd4ad 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,

Again, changes to this file should not go through my tree.

Re: [PATCH net-next] ipv6: fix sparse warning

[Eric Dumazet]

On Wed, 2014-12-10 at 11:28 +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().

This probably should be sent to lkml and CC Paul E. McKenney

Re: [PATCH net-next] ipv6: fix sparse warning

[Ying Xue]

On 12/10/2014 01:40 PM, Eric Dumazet wrote:
> On Wed, 2014-12-10 at 11:28 +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().
> 
> This probably should be sent to lkml and CC Paul E. McKenney
> 
> 
> 
> 

I prefer that the patch as well as another similar patch ("tipc: fix RCU
sparse error") are still based on net-next tree, but I will CC Paul E.
McKenney and lkml when resend them, is it ok?

Especially for the patch ("tipc: fix RCU sparse error"), it fixes the
sparse error introduced by the commit 97ede29e80ee ("tipc: convert name
table read-write lock to RCU") which was only merged into net-next tree.

Regards,
Ying