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To: kmacy@freebsd.org
From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: src-committers@freebsd.org, svn-src-user@freebsd.org
Subject: Re: svn commit: r184759 - user/kmacy/HEAD_fast_multi_xmit/sys/net
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In message: <200811080202.mA822D0W098283@svn.freebsd.org>
            Kip Macy <kmacy@FreeBSD.org> writes:
: +#if defined (__GNUC__)
: +  #if #cpu(i386) || defined __i386 || defined i386 || defined __i386__ || #cpu(x86_64) || defined __x86_64__
: +    #define mb()  __asm__ __volatile__ ("sfence;": : :"memory")
: +  #elif #cpu(sparc64) || defined sparc64 || defined __sparcv9 
: +    #define mb()  __asm__ __volatile__ ("membar #MemIssue": : :"memory")
: +  #elif #cpu(sparc) || defined sparc || defined __sparc__
: +    #define mb()  __asm__ __volatile__ ("stbar;": : :"memory")
: +  #else
: +    #define mb() 	/* XXX just to make this compile */
: +  #endif
: +#else
: +  #error "unknown compiler"
: +#endif

I thought that gcc had a sequence that did this in a platform
independent way.  should I dig it up for you?

Warner