From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 15 Dec 2014 11:27:36 +0100 (CET) From: Daniel Walter Message-ID: <1164899144.1350.1418639256356.JavaMail.root@0x90.at> In-Reply-To: <1418216535-29295-1-git-send-email-richard@nod.at> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [uml-devel] [PATCH] um: Skip futex_atomic_cmpxchg_inatomic() test To: Richard Weinberger Cc: arnd@arndb.de, miklos@szeredi.hu, linux-kernel@vger.kernel.org, geert@linux-m68k.org, lftan@altera.com, user-mode-linux-devel@lists.sourceforge.net List-ID: ----- Original Message ----- > From: "Richard Weinberger" > To: user-mode-linux-devel@lists.sourceforge.net > Cc: arnd@arndb.de, miklos@szeredi.hu, "Richard Weinberger" , 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 > Suggested-by: Geert Uytterhoeven > Signed-off-by: Richard Weinberger > --- > 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