From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <ak@muc.de>
Date: Tue, 04 Jan 2005 19:46:50 +0000
Subject: Re: page fault scalability patch V14 [5/7]: x86_64 atomic pte
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List-Id: <linux-ia64.vger.kernel.org>
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In-Reply-To: <Pine.LNX.4.58.0501041137410.805@schroedinger.engr.sgi.com> (Christoph
 Lameter's message of "Tue, 4 Jan 2005 11:38:20 -0800 (PST)")
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To: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>, akpm@osdl.org, Nick Piggin <nickpiggin@yahoo.com.au>, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org

Christoph Lameter <clameter@sgi.com> writes:

I bet this has been never tested.

>  #define pmd_populate_kernel(mm, pmd, pte) \
>  		set_pmd(pmd, __pmd(_PAGE_TABLE | __pa(pte)))
>  #define pud_populate(mm, pud, pmd) \
> @@ -14,11 +18,24 @@
>  #define pgd_populate(mm, pgd, pud) \
>  		set_pgd(pgd, __pgd(_PAGE_TABLE | __pa(pud)))
>
> +#define pmd_test_and_populate(mm, pmd, pte) \
> +		(cmpxchg((int *)pmd, PMD_NONE, _PAGE_TABLE | __pa(pte)) = PMD_NONE)
> +#define pud_test_and_populate(mm, pud, pmd) \
> +		(cmpxchg((int *)pgd, PUD_NONE, _PAGE_TABLE | __pa(pmd)) = PUD_NONE)
> +#define pgd_test_and_populate(mm, pgd, pud) \
> +		(cmpxchg((int *)pgd, PGD_NONE, _PAGE_TABLE | __pa(pud)) = PGD_NONE)
> +

Shouldn't this all be (long *)pmd ? page table entries on x86-64 are 64bit.
Also why do you cast at all? i think the macro should handle an arbitary
pointer.

> +
>  static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd, struct page *pte)
>  {
>  	set_pmd(pmd, __pmd(_PAGE_TABLE | (page_to_pfn(pte) << PAGE_SHIFT)));
>  }
>
> +static inline int pmd_test_and_populate(struct mm_struct *mm, pmd_t *pmd, struct page *pte)
> +{
> +	return cmpxchg((int *)pmd, PMD_NONE, _PAGE_TABLE | (page_to_pfn(pte) << PAGE_SHIFT)) = PMD_NONE;

Same.

-Andi