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Date: Thu, 01 Oct 2009 08:59:44 +0200
From: Eric Dumazet <eric.dumazet@gmail.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
       Arjan van de Ven <arjan@infradead.org>,
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       Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [GIT PULL] scheduler fixes
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Ingo Molnar a écrit :


> The way to check for a disabled option in a Make rule is:
> 
> 	ifneq ($(CONFIG_X86_CMPXCHG64),y)
> 

Ah OK, thanks for the explanation, my test 486-build (before your change) just finished to :

arch/x86/built-in.o:(__ksymtab+0xa8): undefined reference to `cmpxchg8b_emu'
kernel/built-in.o: In function `sched_clock_local':
/opt/src/linux-2.6/kernel/sched_clock.c:130: undefined reference to `cmpxchg8b_emu'
kernel/built-in.o: In function `sched_clock_remote':
/opt/src/linux-2.6/kernel/sched_clock.c:166: undefined reference to `cmpxchg8b_emu'
make: *** [.tmp_vmlinux1] Error 1



> 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


Thats perfect this fixed my 486-build, thanks again.

Looking at disassembly I still see atomic64_cmpxchg(),
atomic64_xchg(), atomic64_add_return(),  and friends being
included... (but not used)

I'll check if similar patch could be done as well for atomic64 functions.