linux-kernel - Re: [PATCH RFC tools/memory-model 2/5] tools/memory-model: Add litmus test for multicopy atomicity

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Date:   Wed, 18 Apr 2018 11:40:33 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mingo@...nel.org, stern@...land.harvard.edu,
        parri.andrea@...il.com, will.deacon@....com, peterz@...radead.org,
        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 2/5] tools/memory-model: Add
 litmus test for multicopy atomicity

On Mon, Apr 16, 2018 at 09:22:48AM -0700, Paul E. McKenney wrote:
> This commit adds a litmus test suggested by Alan Stern that is forbidden
> on multicopy atomic systems, but allowed on non-multicopy atomic systems.
> Note that other-multicopy atomic systems are examples of non-multicopy
> atomic systems.
> 
> Suggested-by: Alan Stern <stern@...land.harvard.edu>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
>  .../litmus-tests/SB+poonceoncescoh.litmus          | 31 ++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>  create mode 100644 tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus

We seem to be missing an entry in litmus-tests/README...


> 
> diff --git a/tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus b/tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus
> new file mode 100644
> index 000000000000..991a2d6dec63
> --- /dev/null
> +++ b/tools/memory-model/litmus-tests/SB+poonceoncescoh.litmus
> @@ -0,0 +1,31 @@
> +C SB+poonceoncescoh
> +
> +(*
> + * Result: Sometimes
> + *
> + * This litmus test demonstrates that LKMM is not multicopy atomic.
> + *)
> +
> +{}
> +
> +P0(int *x, int *y)
> +{
> +	int r1;
> +	int r2;
> +
> +	WRITE_ONCE(*x, 1);
> +	r1 = READ_ONCE(*x);
> +	r2 = READ_ONCE(*y);
> +}
> +
> +P1(int *x, int *y)
> +{
> +	int r3;
> +	int r4;
> +
> +	WRITE_ONCE(*y, 1);
> +	r3 = READ_ONCE(*y);
> +	r4 = READ_ONCE(*x);
> +}
> +
> +exists (0:r2=0 /\ 1:r4=0 /\ 0:r1=1 /\ 1:r3=1)

This test has a normalised name:  why don't use that?

  Andrea


> -- 
> 2.5.2
>