* [PATCH] rculist: Fix another sparse warning
@ 2015-03-25 4:43 Ying Xue
2015-03-25 13:49 ` Paul E. McKenney
0 siblings, 1 reply; 3+ messages in thread
From: Ying Xue @ 2015-03-25 4:43 UTC (permalink / raw)
To: paulmck; +Cc: linux-kernel
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>
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] rculist: Fix another sparse warning
2015-03-25 4:43 [PATCH] rculist: Fix another sparse warning Ying Xue
@ 2015-03-25 13:49 ` Paul E. McKenney
2015-03-26 5:19 ` Ying Xue
0 siblings, 1 reply; 3+ messages in thread
From: Paul E. McKenney @ 2015-03-25 13:49 UTC (permalink / raw)
To: Ying Xue; +Cc: linux-kernel
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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] rculist: Fix another sparse warning
2015-03-25 13:49 ` Paul E. McKenney
@ 2015-03-26 5:19 ` Ying Xue
0 siblings, 0 replies; 3+ messages in thread
From: Ying Xue @ 2015-03-26 5:19 UTC (permalink / raw)
To: paulmck; +Cc: linux-kernel
On 03/25/2015 09:49 PM, Paul E. McKenney wrote:
> 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().)
>
Yes, you are absolutely right. Thanks to point out my mistake.
I will fix it in next version.
Regards,
Ying
> 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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