Subject: [PATCH V2] ARM: SWP emulation: Restore original *data when failed

From: [email-masked] (Vladimir Murzin)
Date: Tue, 08 Dec 2015 10:22:53 +0000

On 15/10/15 10:30, Shengjiu Wang wrote:
> __user_swpX_asm maybe failed in first STREX operation, emulate_swpX
> will try again, but the *data has been changed in first time. which
> causes the result is wrong.
> This patch is to fix this issue. When STREX succeed, change the *data.
> if it fail, *data is not changed.
> 
> Signed-off-by: Shengjiu Wang <[email-masked]>
> ---
>  arch/arm/kernel/swp_emulate.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
> index 5b26e7e..c3fe769d 100644
> --- a/arch/arm/kernel/swp_emulate.c
> +++ b/arch/arm/kernel/swp_emulate.c
> @@ -36,10 +36,10 @@
>   */
>  #define __user_swpX_asm(data, addr, res, temp, B)		\
>  	__asm__ __volatile__(					\
> -	"	mov		%2, %1\n"			\
> -	"0:	ldrex"B"	%1, [%3]\n"			\
> -	"1:	strex"B"	%0, %2, [%3]\n"			\
> +	"0:	ldrex"B"	%2, [%3]\n"			\
> +	"1:	strex"B"	%0, %1, [%3]\n"			\
>  	"	cmp		%0, #0\n"			\
> +	"	moveq		%1, %2\n"			\
>  	"	movne		%0, %4\n"			\
>  	"2:\n"							\
>  	"	.section	 .text.fixup,\"ax\"\n"		\
> 

I wonder what is status of this patch? I see that arm64 counterpart has
landed in mainline, but I didn't manage to track down this one - is it
because it never been submitted to patch system?

Thanks
Vladimir