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From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Jia Yu <jyu@vmware.com>
Date: Thu, 11 Dec 2014 01:51:01 +0100
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Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] lib: include rte_memory.h for __rte_cache_aligned
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2014-12-09 10:22, Neil Horman:
> On Tue, Dec 09, 2014 at 09:53:18AM +0100, Olivier MATZ wrote:
> > 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
>
> So, that is a great explination, and would be good to have in the changelog.
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Applied with Olivier's explanation.
Thanks
--
Thomas