linux-kernel - RE: [PATCH] mm: disable split page table lock for !MMU

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Message-Id: <20140226140040.8E07AE0098@blue.fi.intel.com>
Date:	Wed, 26 Feb 2014 16:00:40 +0200 (EET)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH] mm: disable split page table lock for !MMU

(Oops. CC: lists)

Kirill A. Shutemov wrote:
> There's no reason to enable split page table lock if don't have page
> tables.
> 
> It also triggers build error at least on ARM since we don't define
> pmd_page() for !MMU.
> 
> In file included from arch/arm/kernel/asm-offsets.c:14:0:
> include/linux/mm.h: In function 'pte_lockptr':
> include/linux/mm.h:1392:2: error: implicit declaration of function 'pmd_page' [-Werror=implicit-function-declaration]
> include/linux/mm.h:1392:2: warning: passing argument 1 of 'ptlock_ptr' makes pointer from integer without a cast [enabled by default]
> include/linux/mm.h:1384:27: note: expected 'struct page *' but argument is of type 'int'
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  mm/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 2d9f1504d75e..90bd85ea6035 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -216,6 +216,7 @@ config PAGEFLAGS_EXTENDED
>  #
>  config SPLIT_PTLOCK_CPUS
>  	int
> +	default "999999" if !MMU
>  	default "999999" if ARM && !CPU_CACHE_VIPT
>  	default "999999" if PARISC && !PA20
>  	default "4"
> -- 
> 1.9.0

-- 
 Kirill A. Shutemov
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