linux-kernel - Re: MMIO and gcc re-ordering issue

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Message-ID: <20080526212010.664302cf@infradead.org>
Date:	Mon, 26 May 2008 21:20:10 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Roland Dreier <rdreier@...co.com>
Cc:	David Miller <davem@...emloft.net>, benh@...nel.crashing.org,
	linux-arch@...r.kernel.org, scottwood@...escale.com,
	linuxppc-dev@...abs.org, alan@...rguk.ukuu.org.uk,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	tpiepho@...escale.com
Subject: Re: MMIO and gcc re-ordering issue

On Mon, 26 May 2008 21:08:10 -0700
Roland Dreier <rdreier@...co.com> wrote:

>  > either via sparse or some fancy lockdep like "device store" thing?
>  > If we can't test for it and it doesn't show up on x86 ... it'll
>  > just be an eterrnal chase.
> 
> Ben's point is that it will start showing up on x86 because newer
> compilers are reordering things...
> 
>  - R.


I know a basic reorder will show up there. A simple "barrier()" in
readl/writel solves it for x86. Understandably, Ben doesn't really like
that answer ;-)

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