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Date:   Thu, 12 Apr 2018 20:52:50 +0800
From:   Boqun Feng <boqun.feng@gmail.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org,
        Alan Stern <stern@rowland.harvard.edu>,
        Andrea Parri <parri.andrea@gmail.com>,
        Will Deacon <will.deacon@arm.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        David Howells <dhowells@redhat.com>,
        Jade Alglave <j.alglave@ucl.ac.uk>,
        Luc Maranget <luc.maranget@inria.fr>,
        Akira Yokosawa <akiyks@gmail.com>
Subject: Re: [PATCH] memory-model: fix cheat sheet typo
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On Wed, Apr 11, 2018 at 07:06:36PM +0200, Paolo Bonzini wrote:
> On 11/04/2018 18:31, Peter Zijlstra wrote:
> >>>                                    Prior Operation   Subsequent Opera=
tion
> >>>                                    ---------------   ----------------=
-----
> >>>                                    R  W  RMW  SV     R  W  DR  DW  RM=
W  SV
> >>>                                    -  -  ---  --     -  -  --  --  --=
-  --
> >>> smp_store_mb()                     Y  Y    Y   Y      Y  Y   Y   Y   =
Y   Y
> > I'm not sure about that, the generic version of that reads:
> >=20
> > include/asm-generic/barrier.h:#define __smp_store_mb(var, value)
> >     do { WRITE_ONCE(var, value); __smp_mb(); } while (0)
> >=20
> > Which doesn't not have an smp_mb() before, so it doesn't actually order
> > prior; or I'm failing to read the table wrong.
>=20
> You're not, even better reason to document it. :)  I was going from
> memory for the x86 version.
>=20
> I'll start tomorrow on fixes to the current document, while we discuss
> the split format and what to do about cumulativity and propagation.
>=20

Besides, since smp_store_mb() is a store, so there is no DR or DW for
the subsequent operations I think, because dependencies come from a read
rather than a write.

Regards,
Boqun

> Paolo

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