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From: David Howells <dhowells@redhat.com>
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Subject: Re: [PATCH] Document Linux's memory barriers [try #2] 
Date: Wed, 08 Mar 2006 19:08:42 +0000
Message-ID: <14275.1141844922@warthog.cambridge.redhat.com>
Sender: linux-arch-owner@vger.kernel.org
To: Alan Cox <alan@redhat.com>
Cc: David Howells <dhowells@redhat.com>, torvalds@osdl.org, akpm@osdl.org, mingo@redhat.com, linux-arch@vger.kernel.org, linuxppc64-dev@ozlabs.org, linux-kernel@vger.kernel.org
List-ID: <linux-arch.vger.kernel.org>

Alan Cox <alan@redhat.com> wrote:

> 	spin_lock(&foo->lock);
> 	writel(0, &foo->regnum);

I presume there only needs to be an mmiowb() here if you've got the
appropriate CPU's I/O memory window set up to be weakly ordered.

> 	writel(1, &foo->data);
> 	mmiowb();
> 	spin_unlock(&foo->lock);

David