[PATCH net-next RESEND 0/2] fix rculist sparse errors

[PATCH net-next RESEND 0/2] fix rculist sparse errors

[Ying Xue]

When hlist_for_each_entry_continue_rcu_bh() gets "next" pointer of
hlist_node structure through rcu_dereference_bh(), sparse warning
appears as the "next" pointer is not annotated as __rcu. So if
the "next" pointer is accessed with hlist_next_rcu() macro, the
__rcu annotation will be added to the pointer. As a consequence,
sparse warning is eliminated too.

The similar errors also appear in hlist_for_each_entry_continue_rcu()
and hlist_for_each_entry_from_rcu().

In this version, CC more people like Paul E. McKenney and lkml mail
list.

Ying Xue (2):
  tipc: fix RCU sparse error
  ipv6: fix sparse warning

 include/linux/rculist.h |   20 ++++++++++----------
 net/tipc/name_table.c   |    6 +++---
 2 files changed, 13 insertions(+), 13 deletions(-)

-- 
1.7.9.5

[PATCH net-next RESEND 1/2] tipc: fix RCU sparse error

[Ying Xue]

The commit 97ede29e80ee ("tipc: convert name table read-write lock to
RCU") involves the following sparse when using

  make ARCH=x86_64 allmodconfig
  make C=1 CF=-D__CHECK_ENDIAN__

net/tipc/name_table.c:1136:17: sparse: incompatible types in comparison expression (different address spaces)
net/tipc/name_table.c:1136:17: sparse: 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_from_rcu().

By the way, this commit also simplifies the way of dereferencing
the first element of a hlist_head list by replacing
hlist_for_each_entry_rcu() with hlist_entry_safe().

Reported-by: Kbuild test robot <kbuild-all@01.org>
Cc: Kbuild test robot <kbuild-all@01.org>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
---
 include/linux/rculist.h |    4 ++--
 net/tipc/name_table.c   |    6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index aa79b3c..866d9c9 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_raw(hlist_next_rcu( \
+			&(pos)->member)), typeof(*(pos)), member))
 
 #endif	/* __KERNEL__ */
 #endif
diff --git a/net/tipc/name_table.c b/net/tipc/name_table.c
index c8df022..fa4341f 100644
--- a/net/tipc/name_table.c
+++ b/net/tipc/name_table.c
@@ -1110,7 +1110,7 @@ static int __tipc_nl_seq_list(struct tipc_nl_msg *msg, u32 *last_type,
 			      u32 *last_lower, u32 *last_publ)
 {
 	struct hlist_head *seq_head;
-	struct name_seq *seq = NULL;
+	struct name_seq *seq;
 	int err;
 	int i;
 
@@ -1127,8 +1127,8 @@ static int __tipc_nl_seq_list(struct tipc_nl_msg *msg, u32 *last_type,
 			if (!seq)
 				return -EPIPE;
 		} else {
-			hlist_for_each_entry_rcu(seq, seq_head, ns_list)
-				break;
+			seq = hlist_entry_safe(rcu_dereference_raw(
+			hlist_first_rcu(seq_head)), struct name_seq, ns_list);
 			if (!seq)
 				continue;
 		}
-- 
1.7.9.5

[PATCH net-next RESEND 2/2] ipv6: fix sparse warning

[Ying Xue]

This fixes the following spare 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 RESEND 2/2] ipv6: fix sparse warning

[Paul E. McKenney]

On Wed, Dec 10, 2014 at 04:46:07PM +0800, Ying Xue wrote:
> This fixes the following spare 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>

If you pull the rculist.h changes from the first patch into this one,
I will queue it up through -rcu.

							Thanx, Paul

> ---
>  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 RESEND 2/2] ipv6: fix sparse warning

[Ying Xue]

On 12/11/2014 12:04 AM, Paul E. McKenney wrote:
> On Wed, Dec 10, 2014 at 04:46:07PM +0800, Ying Xue wrote:
>> This fixes the following spare 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>
> 
> If you pull the rculist.h changes from the first patch into this one,
> I will queue it up through -rcu.
> 

Please just queue this patch into your RCU tree. Some changes of the
first patch currently only exists in net-next tree, so it cannot be
merged into RCU tree now. Therefore, please temporarily ignore it. In
next 3.19 development cycle, I will resubmit it to you.

Thanks,
Ying

> 							Thanx, Paul
> 
>> ---
>>  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 RESEND 2/2] ipv6: fix sparse warning

[Paul E. McKenney]

On Thu, Dec 11, 2014 at 09:56:33AM +0800, Ying Xue wrote:
> On 12/11/2014 12:04 AM, Paul E. McKenney wrote:
> > On Wed, Dec 10, 2014 at 04:46:07PM +0800, Ying Xue wrote:
> >> This fixes the following spare 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>
> > 
> > If you pull the rculist.h changes from the first patch into this one,
> > I will queue it up through -rcu.
> 
> Please just queue this patch into your RCU tree. Some changes of the
> first patch currently only exists in net-next tree, so it cannot be
> merged into RCU tree now. Therefore, please temporarily ignore it. In
> next 3.19 development cycle, I will resubmit it to you.

Sounds good, but could you please rebase the second patch to be
independent of the first patch?  If you do that, I would be happy
to queue it.

							Thanx, Paul

> Thanks,
> Ying
> 
> > 							Thanx, Paul
> > 
> >> ---
> >>  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 RESEND 0/2] fix rculist sparse errors

[David Miller]

From: Ying Xue <ying.xue@windriver.com>
Date: Wed, 10 Dec 2014 16:46:05 +0800

> When hlist_for_each_entry_continue_rcu_bh() gets "next" pointer of
> hlist_node structure through rcu_dereference_bh(), sparse warning
> appears as the "next" pointer is not annotated as __rcu. So if
> the "next" pointer is accessed with hlist_next_rcu() macro, the
> __rcu annotation will be added to the pointer. As a consequence,
> sparse warning is eliminated too.
> 
> The similar errors also appear in hlist_for_each_entry_continue_rcu()
> and hlist_for_each_entry_from_rcu().
> 
> In this version, CC more people like Paul E. McKenney and lkml mail
> list.

The rculist.h changes should go via Paul's tree, not mine.