linux-kernel - Re: Opinion on ordering of writel vs. stores to RAM

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Message-Id: <200609101019.11608.jbarnes@virtuousgeek.org>
Date:	Sun, 10 Sep 2006 10:19:11 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linus Torvalds <torvalds@...l.org>,
	Paul Mackerras <paulus@...ba.org>,
	linux-kernel@...r.kernel.org, akpm@...l.org,
	segher@...nel.crashing.org, davem@...emloft.net
Subject: Re: Opinion on ordering of writel vs. stores to RAM

On Saturday, September 09, 2006 8:09 am, Alan Cox wrote:
> Ar Sad, 2006-09-09 am 17:23 +1000, ysgrifennodd Benjamin 
Herrenschmidt:
> > The problem is that very few people have any clear idea of what
> > mmiowb is :) In fact, what you described is not the definition of
> > mmiowb according to Jesse
>
> Some of us talked a little about this at Linux Kongress and one
> suggestion so people did understand it was
>
> 	spin_lock_io();
> 	spin_unlock_io();
>
> so that it can be expressed not as a weird barrier op but as part of
> the locking.

That's what IRIX had.  It would let us get rid of mmiowb and avoid doing 
a full sync in writeX, so may be the best option.

Jesse
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