[PATCH] um: Skip futex_atomic_cmpxchg_inatomic() test

[PATCH] um: Skip futex_atomic_cmpxchg_inatomic() test

[Richard Weinberger]

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@szeredi.hu>
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Richard Weinberger <richard@nod.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

Re: [uml-devel] [PATCH] um: Skip futex_atomic_cmpxchg_inatomic() test

[Daniel Walter]

----- Original Message -----
> From: "Richard Weinberger" <richard@nod.at>
> To: user-mode-linux-devel@lists.sourceforge.net
> Cc: arnd@arndb.de, miklos@szeredi.hu, "Richard Weinberger" <richard@nod.at>, linux-kernel@vger.kernel.org,
> geert@linux-m68k.org, lftan@altera.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@szeredi.hu>
> Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Richard Weinberger <richard@nod.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@0x90.at>