Messages in this thread | | | Date | Mon, 17 Nov 2014 13:54:58 -0800 | From | Alexander Duyck <> | Subject | Re: [PATCH 2/4] arch: Add lightweight memory barriers fast_rmb() and fast_wmb() |
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On 11/17/2014 12:52 PM, Linus Torvalds wrote: > On Mon, Nov 17, 2014 at 9:18 AM, Alexander Duyck > <alexander.h.duyck@redhat.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
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