Date: Thu, 24 May 2012 17:46:08 -0500 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Marcel Moolenaar <marcel@freebsd.org>, src-committers@freebsd.org Subject: Re: svn commit: r235931 - head/sys/powerpc/include Message-ID: <4FBEBA30.6050901@freebsd.org> In-Reply-To: <358A54BA-6B8E-4685-8CDD-CCAC305ACA2B@xcllnt.net> References: <201205242045.q4OKjipb059398@svn.freebsd.org> <4FBEA493.4020702@freebsd.org> <EEFFC9C4-7469-4D70-A5C6-7F5CB19CAC28@xcllnt.net> <4FBEB2F3.4060405@freebsd.org> <358A54BA-6B8E-4685-8CDD-CCAC305ACA2B@xcllnt.net>
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On 05/24/12 17:22, Marcel Moolenaar wrote: > > On May 24, 2012, at 3:15 PM, Nathan Whitehorn wrote: > >>>> Summary: >>>> 1. *mb() must be lwsync or sync on all machines, except for wmb() which could be eieio >>>> 2. __ATOMIC_ACQ() must be isync (though could be reduced to lwsync with bus_space changes) >>>> 3. __ATOMIC_REL() must be lwsync or sync >>> >>> This is absolutely not what I concluded from our discussions. I have no idea >>> how we could end up so out of sync... >>> >> >> Thanks for the quick change. No idea how we got out of sync. I find all of this synchronization stuff a little mind-bending, so sorry for any miscommunication. __ATOMIC_ACQ() needed to also be isync on ppc64, so I've fixed that up. Things should be good now. > > Ok. I didn't change wmb() to eieio as I wanted to avoid a pendulum effect. > I'll reread our emails and make sure wmb() is what we think it is and if > so I'll do a followup commit. > FYI, > I don't think it really makes a difference. Basically nothing uses wmb(), and those things that do mostly use it wrong and need sync. So it should probably stay as [lw]sync. -Nathan
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