From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Hitoshi Mitake <h.mitake@gmail.com>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
Roland Dreier <roland@purestorage.com>,
Andrew Morton <akpm@linux-foundation.org>,
James Bottomley <James.Bottomley@parallels.com>,
linux-kernel@vger.kernel.org, hpa@linux.intel.com
Subject: Re: [PATCH] NVMe: Fix compilation on architecturs without readq/writeq
Date: Tue, 31 Jan 2012 12:18:20 +0000 [thread overview]
Message-ID: <20120131121820.58a1db97@pyramind.ukuu.org.uk> (raw)
In-Reply-To: <20120131120922.GD32010@elte.hu>
On Tue, 31 Jan 2012 13:09:22 +0100
Ingo Molnar <mingo@elte.hu> wrote:
>
> * Alan Cox <alan@lxorguk.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
next prev parent reply other threads:[~2012-01-31 12:17 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 1:01 [PATCH] NVMe: Fix compilation on architecturs without readq/writeq Matthew Wilcox
2012-01-20 1:21 ` Linus Torvalds
2012-01-20 17:43 ` Wilcox, Matthew R
2012-01-21 8:28 ` Ingo Molnar
2012-01-21 15:54 ` Hitoshi Mitake
2012-01-21 16:58 ` Ingo Molnar
2012-01-23 16:05 ` Hitoshi Mitake
2012-01-23 16:57 ` Linus Torvalds
2012-01-23 23:04 ` H. Peter Anvin
2012-01-29 8:02 ` Hitoshi Mitake
2012-01-31 3:03 ` Linus Torvalds
2012-01-31 3:05 ` Linus Torvalds
2012-02-04 15:25 ` Hitoshi Mitake
2012-01-31 11:58 ` Alan Cox
2012-01-31 12:09 ` Ingo Molnar
2012-01-31 12:18 ` Alan Cox [this message]
2012-01-31 12:23 ` Ingo Molnar
2012-02-01 23:35 ` Linus Torvalds
2012-02-02 1:05 ` James Bottomley
2012-02-02 1:15 ` Linus Torvalds
2012-02-02 15:05 ` H. Peter Anvin
2012-02-04 15:39 ` Hitoshi Mitake
2012-02-05 6:53 ` Geert Uytterhoeven
2012-02-05 7:01 ` Hitoshi Mitake
2012-02-04 15:34 ` Hitoshi Mitake
2012-02-07 2:48 ` Hitoshi Mitake
2012-02-04 15:24 ` Hitoshi Mitake
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