From: Richard Weinberger <richard@nod.at>
Date: Wed, 10 Dec 2014 12:53:51 +0000 (+0100)
Subject: um: Skip futex_atomic_cmpxchg_inatomic() test
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=914f02cd94750cfdf70004d9e086ee51abd84c7b;p=linux-edison.git

um: Skip futex_atomic_cmpxchg_inatomic() test

commit f911d731054ab3d82ee72a16b889e17ca3a2332a upstream.

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>
Tested-by: Daniel Walter <d.walter@0x90.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
index bceee6623b0..d1ff46c0559 100644
--- a/arch/um/Kconfig.common
+++ b/arch/um/Kconfig.common
@@ -8,6 +8,7 @@ config UML
 	default y
 	select HAVE_GENERIC_HARDIRQS
 	select HAVE_UID16
+	select HAVE_FUTEX_CMPXCHG if FUTEX
 	select GENERIC_IRQ_SHOW
 	select GENERIC_CPU_DEVICES
 	select GENERIC_IO