Re: [dpdk-dev] lib: include rte_memory.h for __rte_cache_aligned

[Jia Yu <jyu@vmware.com>]

Yes, Olivier¹s observation is consistent with ours. Compilation didn¹t
complain
if rte_memory.h is not included.

Currently, the lib files indirectly included rte_mbuf.h or rte_mempool.h.
These two header files already included rte_memory.h. Therefore without
this patch, things still work (as validated by parole).

For good practice, it¹s better to explicitly include rte_memory.h to avoid
the problem.

Thanks,
Jia



On 12/9/14, 12:53 AM, "Olivier MATZ" <olivier.matz@6wind.com> wrote:

>Hi Neil,
>
>On 12/08/2014 04:04 PM, Neil Horman wrote:
>> On Fri, Nov 07, 2014 at 09:28:09AM -0800, Jia Yu wrote:
>>> Include rte_memory.h for lib files that use __rte_cache_aligned
>>> attribute.
>>>
>>> Signed-off-by: Jia Yu <jyu@vmware.com>
>>>
>> Why?  I presume there was a build break or something.  Please repost
>>with a
>> changelog that details what this patch is for.
>> Neil
>
>I don't know if Yu's issue was the same, but I had a very "fun" issue
>with __rte_cache_aligned in my application. Consider the following code:
>
>	struct per_core_foo {
>		...
>	} __rte_cache_aligned;
>
>	struct global_foo {
>		struct per_core_foo foo[RTE_MAX_CORE];
>	};
>
>If __rte_cache_aligned is not defined (rte_memory.h is not included),
>the code compiles but the structure is not aligned... it defines the
>structure and creates a global variable called __rte_cache_aligned.
>And this can lead to really bad things if this code is in a .h that
>is included by files that may or may not include rte_memory.h
>
>I have no idea about how we could prevent this issue, except using
>__attribute__((aligned(CACHE_LINE))) instead of __rte_cache_aligned.
>
>Anyway this could probably explain the willing to include rte_memory.h
>everywhere.
>
>Regards,
>Olivier
>