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From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Jia Yu <jyu@vmware.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] lib: include rte_memory.h for __rte_cache_aligned
Date: Thu, 11 Dec 2014 01:51:01 +0100
Message-ID: <1519285.2rmHEkrl95@xps13> (raw)
In-Reply-To: <20141209152204.GD28871@hmsreliant.think-freely.org>

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

      parent reply	other threads:[~2014-12-11  0:51 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-07 17:28 [dpdk-dev] [PATCH] " Jia Yu
2014-11-10  9:46 ` Thomas Monjalon
2014-11-17 19:07   ` Jia Yu
2014-12-08 15:04 ` [dpdk-dev] " Neil Horman
2014-12-09  8:53   ` Olivier MATZ
2014-12-09  9:11     ` Jia Yu
2014-12-09 15:22     ` Neil Horman
2014-12-10 19:09       ` Jia Yu
2014-12-11  0:28         ` Neil Horman
2014-12-11  0:36           ` Thomas Monjalon
2014-12-11 14:17             ` Neil Horman
2014-12-11 21:14               ` Thomas Monjalon
2014-12-11  0:51       ` Thomas Monjalon [this message]

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