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Date: Fri, 27 Sep 2013 16:50:07 +0200
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] checkpatch: Make the memory barrier test noisier
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To: Joe Perches <joe@perches.com>
Cc: Ingo Molnar <mingo@kernel.org>, Tim Chen <tim.c.chen@linux.intel.com>, Jason Low <jason.low2@hp.com>, Davidlohr Bueso <davidlohr@hp.com>, Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, Alex Shi <alex.shi@linaro.org>, Andi Kleen <andi@firstfloor.org>, Michel Lespinasse <walken@google.com>, Davidlohr Bueso <davidlohr.bueso@hp.com>, Matthew R Wilcox <matthew.r.wilcox@intel.com>, Dave Hansen <dave.hansen@intel.com>, Rik van Riel <riel@redhat.com>, Peter Hurley <peter@hurleysoftware.com>, linux-kernel@vger.kernel.org, linux-mm <linux-mm@kvack.org>

On Fri, Sep 27, 2013 at 07:34:55AM -0700, Joe Perches wrote:
> That would make it seem as if all barriers are SMP no?

I would think any memory barrier is ordering against someone else; if
not smp then a device/hardware -- like for instance the hardware page
table walker.

Barriers are fundamentally about order; and order only makes sense if
there's more than 1 party to the game.

> Maybe just refer to Documentation/memory-barriers.txt
> and/or say something like "please document appropriately"

Documentation/memory-barriers.txt is always good; appropriately doesn't
seem to quantify anything much at all. Someone might think:

/*  */
smp_mb();

appropriate... 

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