linux-kernel - Re: [GIT PULL] scheduler fixes

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Message-ID: <20091001061109.GA21488@elte.hu>
Date:	Thu, 1 Oct 2009 08:11:09 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [GIT PULL] scheduler fixes


* Eric Dumazet <eric.dumazet@...il.com> wrote:

> [PATCH] x86: Dont generate cmpxchg8b_emu if CONFIG_X86_CMPXCHG64=y
> 
> cmpxchg8b_emu helper wont be used if CONFIG_X86_CMPXCHG64=y
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
>  arch/x86/kernel/i386_ksyms_32.c |    2 ++
>  arch/x86/lib/Makefile           |    6 ++++--
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/i386_ksyms_32.c b/arch/x86/kernel/i386_ksyms_32.c
> index 1736c5a..9c3bd4a 100644
> --- a/arch/x86/kernel/i386_ksyms_32.c
> +++ b/arch/x86/kernel/i386_ksyms_32.c
> @@ -15,8 +15,10 @@ EXPORT_SYMBOL(mcount);
>   * the export, but dont use it from C code, it is used
>   * by assembly code and is not using C calling convention!
>   */
> +#ifndef CONFIG_X86_CMPXCHG64
>  extern void cmpxchg8b_emu(void);
>  EXPORT_SYMBOL(cmpxchg8b_emu);
> +#endif
>  
>  /* Networking helper routines. */
>  EXPORT_SYMBOL(csum_partial_copy_generic);
> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
> index 3e549b8..c309b82 100644
> --- a/arch/x86/lib/Makefile
> +++ 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

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.

	Ingo
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