linux-kernel - Re: [PATCH memory-model scripts 01/31] tools/memory-model: Document locking corner cases

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Date:   Wed, 22 Mar 2023 12:14:10 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Andrea Parri <parri.andrea@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        kernel-team@...a.com, mingo@...nel.org, stern@...land.harvard.edu,
        will@...nel.org, 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 memory-model scripts 01/31] tools/memory-model:  Document
 locking corner cases

On Wed, Mar 22, 2023 at 09:59:38AM +0100, Andrea Parri wrote:
> >  create mode 100644 Documentation/litmus-tests/locking/DCL-broken.litmus
> >  create mode 100644 Documentation/litmus-tests/locking/DCL-fixed.litmus
> >  create mode 100644 Documentation/litmus-tests/locking/RM-broken.litmus
> >  create mode 100644 Documentation/litmus-tests/locking/RM-fixed.litmus
> 
> Unfortunately none of them were liked by klitmus7/gcc, the diff below
> works for me but please double check.

Applied with attribution, thank you!

I was surprised by the need to change the "locations" clauses, but
applied that change anyway.  Ah, I take it that klitmus prints that,
but doesn't know how to print out a spinlock_t?

Dropping "y" from the "filter" clause also gave me pause, but I eventually
convinced myself that it was OK.  But it would be good for others to
also take a close look.

							Thanx, Paul

>   Andrea
> 
> 
> diff --git a/Documentation/litmus-tests/locking/DCL-broken.litmus b/Documentation/litmus-tests/locking/DCL-broken.litmus
> index cfaa25ff82b1e..bfb7ba4316d69 100644
> --- a/Documentation/litmus-tests/locking/DCL-broken.litmus
> +++ b/Documentation/litmus-tests/locking/DCL-broken.litmus
> @@ -10,10 +10,9 @@ C DCL-broken
>  {
>  	int flag;
>  	int data;
> -	int lck;
>  }
>  
> -P0(int *flag, int *data, int *lck)
> +P0(int *flag, int *data, spinlock_t *lck)
>  {
>  	int r0;
>  	int r1;
> @@ -32,7 +31,7 @@ P0(int *flag, int *data, int *lck)
>  	r2 = READ_ONCE(*data);
>  }
>  
> -P1(int *flag, int *data, int *lck)
> +P1(int *flag, int *data, spinlock_t *lck)
>  {
>  	int r0;
>  	int r1;
> @@ -51,5 +50,5 @@ P1(int *flag, int *data, int *lck)
>  	r2 = READ_ONCE(*data);
>  }
>  
> -locations [flag;data;lck;0:r0;0:r1;1:r0;1:r1]
> +locations [flag;data;0:r0;0:r1;1:r0;1:r1]
>  exists (0:r2=0 \/ 1:r2=0)
> diff --git a/Documentation/litmus-tests/locking/DCL-fixed.litmus b/Documentation/litmus-tests/locking/DCL-fixed.litmus
> index 579d6c246f167..d1b60bcb0c8f3 100644
> --- a/Documentation/litmus-tests/locking/DCL-fixed.litmus
> +++ b/Documentation/litmus-tests/locking/DCL-fixed.litmus
> @@ -11,10 +11,9 @@ C DCL-fixed
>  {
>  	int flag;
>  	int data;
> -	int lck;
>  }
>  
> -P0(int *flag, int *data, int *lck)
> +P0(int *flag, int *data, spinlock_t *lck)
>  {
>  	int r0;
>  	int r1;
> @@ -33,7 +32,7 @@ P0(int *flag, int *data, int *lck)
>  	r2 = READ_ONCE(*data);
>  }
>  
> -P1(int *flag, int *data, int *lck)
> +P1(int *flag, int *data, spinlock_t *lck)
>  {
>  	int r0;
>  	int r1;
> @@ -52,5 +51,5 @@ P1(int *flag, int *data, int *lck)
>  	r2 = READ_ONCE(*data);
>  }
>  
> -locations [flag;data;lck;0:r0;0:r1;1:r0;1:r1]
> +locations [flag;data;0:r0;0:r1;1:r0;1:r1]
>  exists (0:r2=0 \/ 1:r2=0)
> diff --git a/Documentation/litmus-tests/locking/RM-broken.litmus b/Documentation/litmus-tests/locking/RM-broken.litmus
> index c586ae4b547de..b7ef30cedfe51 100644
> --- a/Documentation/litmus-tests/locking/RM-broken.litmus
> +++ b/Documentation/litmus-tests/locking/RM-broken.litmus
> @@ -9,12 +9,11 @@ C RM-broken
>   *)
>  
>  {
> -	int lck;
>  	int x;
> -	int y;
> +	atomic_t y;
>  }
>  
> -P0(int *x, int *y, int *lck)
> +P0(int *x, atomic_t *y, spinlock_t *lck)
>  {
>  	int r2;
>  
> @@ -24,7 +23,7 @@ P0(int *x, int *y, int *lck)
>  	spin_unlock(lck);
>  }
>  
> -P1(int *x, int *y, int *lck)
> +P1(int *x, atomic_t *y, spinlock_t *lck)
>  {
>  	int r0;
>  	int r1;
> @@ -37,6 +36,6 @@ P1(int *x, int *y, int *lck)
>  	spin_unlock(lck);
>  }
>  
> -locations [x;lck;0:r2;1:r0;1:r1;1:r2]
> -filter (y=2 /\ 1:r0=0 /\ 1:r1=1)
> +locations [x;0:r2;1:r0;1:r1;1:r2]
> +filter (1:r0=0 /\ 1:r1=1)
>  exists (1:r2=1)
> diff --git a/Documentation/litmus-tests/locking/RM-fixed.litmus b/Documentation/litmus-tests/locking/RM-fixed.litmus
> index 672856736b42e..b628175596160 100644
> --- a/Documentation/litmus-tests/locking/RM-fixed.litmus
> +++ b/Documentation/litmus-tests/locking/RM-fixed.litmus
> @@ -9,12 +9,11 @@ C RM-fixed
>   *)
>  
>  {
> -	int lck;
>  	int x;
> -	int y;
> +	atomic_t y;
>  }
>  
> -P0(int *x, int *y, int *lck)
> +P0(int *x, atomic_t *y, spinlock_t *lck)
>  {
>  	int r2;
>  
> @@ -24,7 +23,7 @@ P0(int *x, int *y, int *lck)
>  	spin_unlock(lck);
>  }
>  
> -P1(int *x, int *y, int *lck)
> +P1(int *x, atomic_t *y, spinlock_t *lck)
>  {
>  	int r0;
>  	int r1;
> @@ -37,6 +36,6 @@ P1(int *x, int *y, int *lck)
>  	spin_unlock(lck);
>  }
>  
> -locations [x;lck;0:r2;1:r0;1:r1;1:r2]
> -filter (y=2 /\ 1:r0=0 /\ 1:r1=1)
> +locations [x;0:r2;1:r0;1:r1;1:r2]
> +filter (1:r0=0 /\ 1:r1=1)
>  exists (1:r2=1)