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Date:	Mon, 17 Nov 2014 12:52:17 -0800
From:	Linus Torvalds <>
To:	Alexander Duyck <>
Cc:	"" <>,
	Network Development <>,
	Linux Kernel Mailing List <>,
	Mathieu Desnoyers <>,
	Peter Zijlstra <>,
	Benjamin Herrenschmidt <>,
	Heiko Carstens <>,
	Ingo Molnar <>,
	Michael Neuling <>,
	Russell King - ARM Linux <>,,,
	Geert Uytterhoeven <>,
	Jeff Kirsher <>,
	Francois Romieu <>,
	Paul McKenney <>,, Will Deacon <>,
	Michael Ellerman <>,
	Tony Luck <>,
	Oleg Nesterov <>,
	Martin Schwidefsky <>,
	Frédéric Weisbecker <>,
	David Miller <>
Subject: Re: [PATCH 2/4] arch: Add lightweight memory barriers fast_rmb() and fast_wmb()

On Mon, Nov 17, 2014 at 9:18 AM, Alexander Duyck
<> wrote:
> There are a number of situations where the mandatory barriers rmb() and
> wmb() are used to order memory/memory operations in the device drivers
> and those barriers are much heavier than they actually need to be.

Ugh. I absolutely despise the name.

It's not "fast". It's just limited. It's the same as "smp_*mb()", in
that it works on cacheable memory, but it actually stays around even
for non-SMP builds.

So I think the name is actively misleading.

Naming should be about what it does, not about some kind of PR thing
that confuses people into thinking it's "better".

Maybe "dma_*mb()" would be acceptable, and ends up having the same
naming convention as "smb_*mb()", and explains what it's about.

And yes, in the same spirit, it would probably be good to try to
eventually get rid of the plain "*mb()" functions, and perhaps call
them "mmio_*mb()" to clarify that they are about ordering memory wrt


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