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SubjectRe: [PATCH] fib_trie: rcu_assign_pointer warning fix
On 12-02-2008 02:16, David Miller wrote:
> From: Stephen Hemminger <shemminger@vyatta.com>
> Date: Mon, 11 Feb 2008 16:59:54 -0800
>
> linux-kernel added to CC:, any change to generic kernel infrastructure
> should be posted there
>
>> Eliminate warnings when rcu_assign_pointer is used with unsigned long.
>> It is reasonable to use RCU with non-pointer values so allow it for general
>> use. Add a comment to explain the if test.
>>
>> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
>> ---
>> include/linux/rcupdate.h | 13 +++++++------
>> 1 files changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
>> index 37a642c..c44ac87 100644
>> --- a/include/linux/rcupdate.h
>> +++ b/include/linux/rcupdate.h
>> @@ -172,14 +172,15 @@ struct rcu_head {
>> * structure after the pointer assignment. More importantly, this
>> * call documents which pointers will be dereferenced by RCU read-side
>> * code.
>> + *
>> + * If value is the NULL (constant 0), then no barrier is needed.
>> */
>>
>> -#define rcu_assign_pointer(p, v) \
>> - ({ \
>> - if (!__builtin_constant_p(v) || \
>> - ((v) != NULL)) \
>> - smp_wmb(); \
>> - (p) = (v); \
>> +#define rcu_assign_pointer(p, v) \
>> + ({ \
>> + if (!(__builtin_constant_p(v) && v)) \

...But, "If value is the NULL (constant 0)" we have:

if (!(1 && NULL != 0)) ==> if (!(0)) and the barrier is used?!
>> + smp_wmb(); \
>> + (p) = (v); \
>> })
>>
>> /**


Regards,
Jarek P.


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