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Date: Mon, 17 Nov 2014 13:54:58 -0800 From: Alexander Duyck <alexander.h.duyck@...hat.com> To: Linus Torvalds <torvalds@...ux-foundation.org> CC: "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, Peter Zijlstra <peterz@...radead.org>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Heiko Carstens <heiko.carstens@...ibm.com>, Ingo Molnar <mingo@...nel.org>, Michael Neuling <mikey@...ling.org>, Russell King - ARM Linux <linux@....linux.org.uk>, donald.c.skidmore@...el.com, matthew.vick@...el.com, Geert Uytterhoeven <geert@...ux-m68k.org>, Jeff Kirsher <jeffrey.t.kirsher@...el.com>, Francois Romieu <romieu@...zoreil.com>, Paul McKenney <paulmck@...ux.vnet.ibm.com>, nic_swsd@...ltek.com, Will Deacon <will.deacon@....com>, Michael Ellerman <michael@...erman.id.au>, Tony Luck <tony.luck@...el.com>, Oleg Nesterov <oleg@...hat.com>, Martin Schwidefsky <schwidefsky@...ibm.com>, Frédéric Weisbecker <fweisbec@...il.com>, David Miller <davem@...emloft.net> Subject: Re: [PATCH 2/4] arch: Add lightweight memory barriers fast_rmb() and fast_wmb() On 11/17/2014 12:52 PM, Linus Torvalds wrote: > On Mon, Nov 17, 2014 at 9:18 AM, Alexander Duyck > <alexander.h.duyck@...hat.com> 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. What would you think of the name "coherent_*mb()"? I would prefer to avoid dma in the name since, at least in my mind, that implies MMIO. It also ties in well with dma_alloc_coherent/dma_free_coherent which is what would typically be used to allocate the memory we would be using the barrier to protect anyway. > 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 > mmio. > > Hmm? > > Linus I will work on pulling all of the coherent barrier cases out of using the plain "*mb()" calls first. We need to sort that out before we could look at renaming the plain barrier functions. - Alex -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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