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Message-ID: <20120131121820.58a1db97@pyramind.ukuu.org.uk>
Date: Tue, 31 Jan 2012 12:18:20 +0000
From: Alan Cox <alan@...rguk.ukuu.org.uk>
To: Ingo Molnar <mingo@...e.hu>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Hitoshi Mitake <h.mitake@...il.com>,
Matthew Wilcox <matthew.r.wilcox@...el.com>,
Roland Dreier <roland@...estorage.com>,
Andrew Morton <akpm@...ux-foundation.org>,
James Bottomley <James.Bottomley@...allels.com>,
linux-kernel@...r.kernel.org, hpa@...ux.intel.com
Subject: Re: [PATCH] NVMe: Fix compilation on architecturs without
readq/writeq
On Tue, 31 Jan 2012 13:09:22 +0100
Ingo Molnar <mingo@...e.hu> wrote:
>
> * Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>
> > > u64 val;
> > > val = readl(addr);
> > > val |= readl(addr+4) << 32;
> > >
> > > is well-defined and must read the low word first - both at the C level
> > > *and* at the CPU level. Anything else would be a bug in the
> > > architecture "readl()" implementation or the hardware.
> >
> > That doesn't make the access atomic to hardware however as a true 64bit
> > readq/writeq would be ?
> >
> > It seems to me the two are not quite the same semantically
>
> Correct, and that's what the:
>
> #include <asm/io-inatomic.h>
>
> line in the driver would express.
Why would "inatomic" indicate that - I'm confused. It would imply to me
they were extra specially atomic ?
(atomos if from the Greek so in- as a prefix isn't the same in- as in
many other words, welcome to English hell - who needs perl)
non-atomic.h might be better, or 'un-atomic' or 'multi-read' or
something ?
Alan
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