From: David Howells <dhowells@redhat.com>
To: "David S. Miller" <davem@davemloft.net>
Cc: matthew@wil.cx, anton@samba.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH] ?mb() -> smp_?mb() conversion
Date: Tue, 22 Mar 2005 18:00:15 +0000 [thread overview]
Message-ID: <12463.1111514415@redhat.com> (raw)
In-Reply-To: <20050322091331.7b2967a1.davem@davemloft.net>
David S. Miller <davem@davemloft.net> wrote:
> > I don't think these actually exist at the moment. My suggestion was that we
> > rename {r,w,}mb() to io_{r,w,}mb().
>
> This is the first time I've seen that ?mb() should order I/O
> accesses. My sparc64 versions certainly don't handle that
> correctly. :-) That being said, I think we're all being
> educated to so me extent in this thread.
The FRV CPUs have a MEMBAR instruction; it takes no parameters and acts as a
mb().
You need this when accessing memory-mapped I/O (which is all I/O). Otherwise
reads and writes to peripherals may cross under some circumstances.
We've implemented the logic of when to insert MEMBAR into the FRV compiler,
using __builtin_read8/16/32() and __builtin_write8/16/32().
David
next prev parent reply other threads:[~2005-03-22 18:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-21 22:59 [PATCH] ?mb() -> smp_?mb() conversion Anton Blanchard
2005-03-21 23:06 ` David S. Miller
2005-03-22 10:43 ` David Howells
2005-03-22 13:13 ` Matthew Wilcox
2005-03-22 14:27 ` David Howells
2005-03-22 16:03 ` Anton Blanchard
2005-03-22 16:34 ` Matthew Wilcox
2005-03-22 16:48 ` David Howells
2005-03-22 17:13 ` David S. Miller
2005-03-22 17:44 ` James Bottomley
2005-03-22 18:09 ` Jesse Barnes
2005-03-22 18:00 ` David Howells [this message]
2005-03-22 21:59 ` Paul Mackerras
2005-03-22 18:15 ` Jesse Barnes
2005-03-22 18:24 ` Jesse Barnes
2005-03-23 6:23 ` Paul Mackerras
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