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DateWed, 14 Dec 2005 02:12:53 +0100
FromAndi Kleen <>
SubjectRe: Semantics of smp_mb() [was : Re: [PATCH] Fix RCU race in access of nohz_cpu_mask ]
On Tue, Dec 13, 2005 at 02:50:59PM -0800, Paul E. McKenney wrote:
> On Wed, Dec 14, 2005 at 09:27:41AM +1100, Keith Owens wrote:
> > On Tue, 13 Dec 2005 08:20:27 -0800,
> > "Paul E. McKenney" <paulmck@us.ibm.com> wrote:
> > >If the variable p references MMIO rather than normal memory, then
> > >wmb() and rmb() are needed instead of smp_wmb() and smp_rmb().
> >
> > mmiowb(), not wmb(). IA64 has a different form of memory fence for I/O
> > space compared to normal memory. MIPS also has a non-empty form of
> > mmiowb().
>
> New one on me!

Didn't it make only a difference on the Altix or something like that?
I suppose they added it only on the drivers for devices supported by SGI.

-Andi
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