From: Ingo Molnar <mingo@elte.hu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
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 13:09:22 +0100 [thread overview]
Message-ID: <20120131120922.GD32010@elte.hu> (raw)
In-Reply-To: <20120131115855.5861bad7@pyramind.ukuu.org.uk>
* 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.
Thanks,
Ingo
next prev parent reply other threads:[~2012-01-31 12:09 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 [this message]
2012-01-31 12:18 ` Alan Cox
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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