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

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Message-ID: <4AC449BD.1060003@gmail.com>
Date:	Thu, 01 Oct 2009 08:18:37 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
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

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

(But I'll re-check in a couple of hours)

extract from arch/x86/include/asm/cmpxchg_32.h :


#ifndef CONFIG_X86_CMPXCHG64


#define cmpxchg64(ptr, o, n)                                    \
({                                                              \
        __typeof__(*(ptr)) __ret;                               \
        __typeof__(*(ptr)) __old = (o);                         \
        __typeof__(*(ptr)) __new = (n);                         \
        alternative_io("call cmpxchg8b_emu",                    \
                        "lock; cmpxchg8b (%%esi)" ,             \
                       X86_FEATURE_CX8,                         \
                       "=A" (__ret),                            \
                       "S" ((ptr)), "0" (__old),                \
                       "b" ((unsigned int)__new),               \
                       "c" ((unsigned int)(__new>>32))          \
                       : "memory");                             \
        __ret; })


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