linux-kernel - Re: [PATCH RFC tools/memory-model] Add s390.{cfg,cat}

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Message-Id: <20180328164922.GA25475@linux.vnet.ibm.com>
Date:   Wed, 28 Mar 2018 09:49:22 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     schwidefsky@...ibm.com, borntraeger@...ibm.com,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        stern@...land.harvard.edu, parri.andrea@...il.com,
        will.deacon@....com, boqun.feng@...il.com, npiggin@...il.com,
        dhowells@...hat.com, j.alglave@....ac.uk, luc.maranget@...ia.fr,
        akiyks@...il.com
Subject: Re: [PATCH RFC tools/memory-model] Add s390.{cfg,cat}

On Wed, Mar 28, 2018 at 07:20:04AM -0700, Paul E. McKenney wrote:
> On Wed, Mar 28, 2018 at 03:48:13PM +0200, Peter Zijlstra wrote:
> > On Wed, Mar 28, 2018 at 06:42:32AM -0700, Paul E. McKenney wrote:
> > > Hello!
> > > 
> > > The prototype patch shown below provides files required to allow herd7 to
> > > evaluate C-language litmus tests for the multicopy-atomic TSO ordering
> > > provided by s390.  
> > 
> > There really isn't anything s390 specific here is there? That is, would
> > this not equally work for x86 and sparc, both of which are similarly TSO
> > ?
> 
> As I understand it, there is a difference.  The difference from TSO
> systems such as x86 is that s390 is multicopy atomic as well as TSO.
> In contrast, x86 is TSO as well as other-multicopy-atomic.  I must defer
> to Martin and Christian for details -- this should be interpreted as a
> feeble first attempt on my part, not any sort of IBM-approved definition
> of s390.  ;-)
> 
> > Given that, should this not be called TSO instead of s390 ?
> 
> I agree completely with a single tso.cfg, TSO.cfg, or whatever name,
> as opposed to a bunch of identical files for x86, SPARC, ...

And to Alan's point, it appears that you can already test x86 TSO ordering
on C-language litmus tests as follows:

	herd7 -conf linux-kernel.cfg -cat x86tso.cat litmus-tests/SB+poonceoncescoh.litmus

Might simply be working by accident, but it does currently work.  ;-)

							Thanx, Paul