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Date: Thu, 1 Oct 2009 08:42:09 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Martin Schwidefsky <schwidefsky@de.ibm.com>,
       Thomas Gleixner <tglx@linutronix.de>, John Stultz <johnstul@us.ibm.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [GIT PULL] scheduler fixes
Message-ID: <20091001064209.GA25189@elte.hu>
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* Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Ingo Molnar a écrit :
> > 
> > That's not enough - the inline assembly code in 
> > arch/x86/include/asm/cmpxchg_32.h should also not reference 
> > cmpxchg8b_emu in that case.
> > 
> 
> I believe it is OK as is, since cmpxchg8b_emu is referenced only
> once, in a section guarded by :
> #ifndef CONFIG_X86_CMPXCHG64

yeah. But this bit is wrong:

> +++ b/arch/x86/lib/Makefile
> @@ -15,8 +15,10 @@ ifeq ($(CONFIG_X86_32),y)
>          obj-y += atomic64_32.o
>          lib-y += checksum_32.o
>          lib-y += strstr_32.o
> -        lib-y += semaphore_32.o string_32.o cmpxchg8b_emu.o
> -
> +        lib-y += semaphore_32.o string_32.o
> +ifeq ($(CONFIG_X86_CMPXCHG64),n)
> +        lib-y += cmpxchg8b_emu.o
> +endif
>          lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o
>  else
>          obj-y += io_64.o iomap_copy_64.o

The way to check for a disabled option in a Make rule is:

	ifneq ($(CONFIG_X86_CMPXCHG64),y)

As in the disabled case the config variable will be undefined. (and wont 
have a value of 'n'). I've done the fix below on your patch.

	Ingo

Index: linux2/arch/x86/lib/Makefile
===================================================================
--- linux2.orig/arch/x86/lib/Makefile
+++ linux2/arch/x86/lib/Makefile
@@ -16,7 +16,7 @@ ifeq ($(CONFIG_X86_32),y)
         lib-y += checksum_32.o
         lib-y += strstr_32.o
         lib-y += semaphore_32.o string_32.o
-ifeq ($(CONFIG_X86_CMPXCHG64),n)
+ifneq ($(CONFIG_X86_CMPXCHG64),y)
         lib-y += cmpxchg8b_emu.o
 endif
         lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o