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Subject: Re: [PATCH]: uClinux (MMU-less) patches against 2.5.28
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Ungerer <gerg@snapgear.com>, linux-kernel@vger.kernel.org,
       David McCullough <davidm@snapgear.com>
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Date: 26 Jul 2002 11:56:04 +0100
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On Fri, 2002-07-26 at 10:39, David Woodhouse wrote:
> 
> alan@lxorguk.ukuu.org.uk said:
> >  It doesn't work with an MMU either. Consider O_DIRECT file writing
> > from such a page
> 
> Hmmm. 
> 
> O_DIRECT writing of data from an XIP-mapped page to a file on the same chip 
> ain't ever going to work. Writing to something elsewhere should be fine -- 
> if a page is locked when the chip driver wants to go talk to the chip, the 
> chip driver has to wait for that page to become unlocked. No?

Now consider two events each locking the page the other wishes to write
to. At that point you may want to stop digging any deeper holes