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Date: Fri, 23 Feb 2001 13:09:02 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Andrea Arcangeli <andrea@suse.de>
cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: Linux 2.4.1-ac15
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On Fri, 23 Feb 2001, Andrea Arcangeli wrote:
> 
> I think that can't happen. Infact I think the whole section:
> 
> 		pmd = pmd_offset(pgd, address);
> 		pmd_k = pmd_offset(pgd_k, address);
> 
> 		if (pmd_present(*pmd) || !pmd_present(*pmd_k))
> 			goto bad_area_nosemaphore;
> 		set_pmd(pmd, *pmd_k);
> 		return;
> 
> is superflows.

No. Think about the differences in PAE and non-PAE mode. 

> The middle pagetable is shared and the pmd_t entry is set by vmalloc itself (it
> just points to the as well shared pte), it's only the pgd that is setup lazily

In non-PAE mode, the pgd entry doesn't exist. pgd_present() returns a
unconditional 1. Its' the pmd functions that kick in then.

		Linus

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