linux-kernel - Re: [PATCH] checkpatch: Make the memory barrier test noisier

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Date:	Sat, 28 Sep 2013 09:54:09 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Joe Perches <joe@...ches.com>, Ingo Molnar <mingo@...nel.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Jason Low <jason.low2@...com>,
	Davidlohr Bueso <davidlohr@...com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Alex Shi <alex.shi@...aro.org>,
	Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Matthew R Wilcox <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] checkpatch: Make the memory barrier test noisier

On Sat, Sep 28, 2013 at 01:40:27AM +0200, Oliver Neukum wrote:
> On Fri, 2013-09-27 at 16:50 +0200, Peter Zijlstra wrote:
> > 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.
> 
> But not necessarily more than 1 kind of parties. It is perfectly
> possible to have a barrier against other threads running the same
> function.

Then that makes a good comment ;-)
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