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[PATCH] s390: more efficient smp barriers

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  [PATCH] s390: more efficient smp barriers "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-10 13:00 +0100
    Re: [PATCH] s390: more efficient smp barriers Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-01-11 09:10 +0100

#1305545 — [PATCH] s390: more efficient smp barriers

As per: lkml.kernel.org/r/20150921112252.3c2937e1@mschwide
atomics imply a barrier on s390, so s390 should change
smp_mb__before_atomic and smp_mb__after_atomic to barrier() instead of
smp_mb() and hence should not use the generic versions.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

This is on top of arch barrier cleanup patchset,
will be included in v3 of that patchset.

 arch/s390/include/asm/barrier.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
index 4d26fa4..5c8db3c 100644
--- a/arch/s390/include/asm/barrier.h
+++ b/arch/s390/include/asm/barrier.h
@@ -45,6 +45,9 @@ do {									\
 	___p1;								\
 })
 
+#define __smp_mb__before_atomic()	barrier()
+#define __smp_mb__after_atomic()	barrier()
+
 #include <asm-generic/barrier.h>
 
 #endif /* __ASM_BARRIER_H */
-- 
MST

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#1305932

On Sun, 10 Jan 2016 13:53:26 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> As per: lkml.kernel.org/r/20150921112252.3c2937e1@mschwide
> atomics imply a barrier on s390, so s390 should change
> smp_mb__before_atomic and smp_mb__after_atomic to barrier() instead of
> smp_mb() and hence should not use the generic versions.
> 
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 
> This is on top of arch barrier cleanup patchset,
> will be included in v3 of that patchset.
> 
>  arch/s390/include/asm/barrier.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
> index 4d26fa4..5c8db3c 100644
> --- a/arch/s390/include/asm/barrier.h
> +++ b/arch/s390/include/asm/barrier.h
> @@ -45,6 +45,9 @@ do {									\
>  	___p1;								\
>  })
> 
> +#define __smp_mb__before_atomic()	barrier()
> +#define __smp_mb__after_atomic()	barrier()
> +
>  #include <asm-generic/barrier.h>
> 
>  #endif /* __ASM_BARRIER_H */

Feel free to add:
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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