linux-kernel - Re: [uml-devel] [PATCH] um: Skip futex_atomic_cmpxchg

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Date:	Mon, 15 Dec 2014 11:27:36 +0100 (CET)
From:	Daniel Walter <sahne@...0.at>
To:	Richard Weinberger <richard@....at>
Cc:	arnd@...db.de, miklos@...redi.hu, linux-kernel@...r.kernel.org,
	geert@...ux-m68k.org, lftan@...era.com,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [uml-devel] [PATCH] um: Skip futex_atomic_cmpxchg_inatomic()
 test

----- Original Message -----
> From: "Richard Weinberger" <richard@....at>
> To: user-mode-linux-devel@...ts.sourceforge.net
> Cc: arnd@...db.de, miklos@...redi.hu, "Richard Weinberger" <richard@....at>, linux-kernel@...r.kernel.org,
> geert@...ux-m68k.org, lftan@...era.com
> Sent: Wednesday, December 10, 2014 1:02:15 PM
> Subject: [uml-devel] [PATCH] um: Skip futex_atomic_cmpxchg_inatomic() test
> 
> futex_atomic_cmpxchg_inatomic() does not work on UML because
> it triggers a copy_from_user() in kernel context.
> On UML copy_from_user() can only be used if the kernel was called
> by a real user space process such that UML can use ptrace()
> to fetch the value.
> 
> Reported-by: Miklos Szeredi <miklos@...redi.hu>
> Suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
>  arch/um/Kconfig.common | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
> index 87bc868..d195a87 100644
> --- a/arch/um/Kconfig.common
> +++ b/arch/um/Kconfig.common
> @@ -3,6 +3,7 @@ config UML
>  	default y
>  	select HAVE_ARCH_AUDITSYSCALL
>  	select HAVE_UID16
> +	select HAVE_FUTEX_CMPXCHG if FUTEX
>  	select GENERIC_IRQ_SHOW
>  	select GENERIC_CPU_DEVICES
>  	select GENERIC_IO
> --
> 2.1.0
> 
Hi,

tested it a few days, looks good.


Tested-by: Daniel Walter <d.walter@...0.at>
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