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Message-ID: <4365736B.4050506@yahoo.com.au>
Date: Mon, 31 Oct 2005 12:29:15 +1100
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Zwane Mwaikambo <zwane@arm.linux.org.uk>
CC: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [patch 1/5] i386 generic cmpxchg
References: <436416AD.3050709@yahoo.com.au> <4364171C.7020103@yahoo.com.au> <Pine.LNX.4.61.0510301157440.1526@montezuma.fsmlabs.com>
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Zwane Mwaikambo wrote:
> Hi Nick,
> 
> On Sun, 30 Oct 2005, Nick Piggin wrote:
> 
> +#define cmpxchg(ptr,o,n)						\
> +({									\
> +	__typeof__(*(ptr)) __ret;					\
> +	if (likely(boot_cpu_data.x86 > 3))				\
> +		__ret = __cmpxchg((ptr), (unsigned long)(o),		\
> +					(unsigned long)(n), sizeof(*(ptr))); \
> +	else								\
> +		__ret = cmpxchg_386((ptr), (unsigned long)(o),		\
> +					(unsigned long)(n), sizeof(*(ptr))); \
> +	__ret;								\
> +})
> +#endif
> 
> How about something similar to the following to remove the branch on 
> optimised kernels?
> 

Hi Zwane,
This is only in the !CONFIG_X86_CMPXCHG case, though, so the branch would
only be there on a 386 kernel, I think?

-- 
SUSE Labs, Novell Inc.

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