linux-kernel - Re: [PATCH v2] barriers: introduce smp_mb__release

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Date:	Fri, 9 Oct 2015 13:41:28 +0100
From:	Will Deacon <will.deacon@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Boqun Feng <boqun.feng@...il.com>,
	Anton Blanchard <anton@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2] barriers: introduce smp_mb__release_acquire and
 update documentation

On Fri, Oct 09, 2015 at 01:02:46PM +0200, Peter Zijlstra wrote:
> On Fri, Oct 09, 2015 at 10:40:39AM +0100, Will Deacon wrote:
> > Stepping back a second, I believe that there are three cases:
> > 
> > 
> >  RELEASE X -> ACQUIRE Y (same CPU)
> >    * Needs a barrier on TSO architectures for full ordering
> 	+PPC
> 
> >  UNLOCK X -> LOCK Y (same CPU)
> >    * Needs a barrier on PPC for full ordering
> 
> 
> >  RELEASE X -> ACQUIRE X (different CPUs)
>     * Fully ordered everywhere...
>     * ... but needs a barrier on TSO + PPC to become a full barrier
> 
> >  UNLOCK X -> ACQUIRE X (different CPUs)
> 
> s/ACQUIRE/LOCK/ ?

Yes, sorry.

Will
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