Date: Mon, 23 Apr 2012 13:40:43 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Fengwei yin <yfw.bsd@gmail.com> Cc: jack.ren@intel.com, freebsd-threads@freebsd.org Subject: Re: About the memory barrier in BSD libc Message-ID: <20120423094043.GS32749@zxy.spb.ru> In-Reply-To: <CAPHpMu=kCwhf1RV_sYBDWDPL8368YTMLXge4L_g_F4AkTX1H5g@mail.gmail.com> References: <CAPHpMu=DOGQ=TuFeYH7bH8hVwteT4Q3k67-mvoOFob6P3Y506w@mail.gmail.com> <20120423084120.GD76983@zxy.spb.ru> <CAPHpMu=kCwhf1RV_sYBDWDPL8368YTMLXge4L_g_F4AkTX1H5g@mail.gmail.com>
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On Mon, Apr 23, 2012 at 05:32:24PM +0800, Fengwei yin wrote:
> On Mon, Apr 23, 2012 at 4:41 PM, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote:
> > On Mon, Apr 23, 2012 at 02:56:03PM +0800, Fengwei yin wrote:
> >
> >> Hi list,
> >> If this is not correct question on the list, please let me know and
> >> sorry for noise.
> >>
> >> I have a question regarding the BSD libc for SMP arch. I didn't see
> >> memory barrier used in libc.
> >> How can we make sure it's safe on SMP arch?
> >
> > /usr/include/machine/atomic.h:
> >
> > #define mb() š š__asm __volatile("lock; addl $0,(%%esp)" : : : "memory")
> > #define wmb() š __asm __volatile("lock; addl $0,(%%esp)" : : : "memory")
> > #define rmb() š __asm __volatile("lock; addl $0,(%%esp)" : : : "memory")
> >
>
> Thanks for the information. But it looks no body use it in libc.
I think no body in libc need memory barrier: libc don't work with
peripheral, for atomic opertions used different macros.
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