linux-kernel - Re: [PATCH 1/2] x86: add user_atomic_cmpxchg

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Message-ID: <52AF3077.1060001@zytor.com>
Date:	Mon, 16 Dec 2013 08:55:19 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Qiaowei Ren <qiaowei.ren@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
CC:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86: add user_atomic_cmpxchg_inatomic at uaccess.h

On 12/13/2013 10:25 PM, Qiaowei Ren wrote:
> +#ifdef CONFIG_X86_64							\
> +	case 8:								\
> +	{								\
> +		asm volatile("\t" ASM_STAC "\n"				\
> +			"1:\t" LOCK_PREFIX "cmpxchgq %4, %2\n"		\
> +			"2:\t" ASM_CLAC "\n"				\
> +			"\t.section .fixup, \"ax\"\n"			\
> +			"3:\tmov     %3, %0\n"				\
> +			"\tjmp     2b\n"				\
> +			"\t.previous\n"					\
> +			_ASM_EXTABLE(1b, 3b)				\
> +			: "+r" (__ret), "=a" (__old), "+m" (*(ptr))	\
> +			: "i" (-EFAULT), "r" (__new), "1" (__old)	\
> +			: "memory"					\
> +		);							\
> +		break;							\
> +	}								\
> +#endif								\

This, of course, doesn't work because this is embedded in a macro.  I
realize I requested it, but you should still have tested it.

Anyway, I'll fix it up.

	-hpa

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