linux-kernel - Re: smp_store

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Date:	Fri, 03 Jul 2015 08:29:48 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	tony.luck@...el.com, heiko.carstens@...ibm.com
Subject: Re: smp_store_mb() oddity..

On Wed, 2015-07-01 at 19:17 +0200, Peter Zijlstra wrote:

> Subject: locking/arch: Make smp_store_mb() use smp_mb()
> 
> Linus noticed that there were a few smp_store_mb() implementations that
> used mb(), which is inconsistent with the new naming.
> 
> Since all smp_store_mb() users really are about SMP ordering, not IO
> ordering, change them all to be consistent.
> 
> Cc: Tony Luck <tony.luck@...el.com>

For powerpc:
Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/ia64/include/asm/barrier.h    | 2 +-
>  arch/powerpc/include/asm/barrier.h | 2 +-
>  arch/s390/include/asm/barrier.h    | 2 +-
>  include/asm-generic/barrier.h      | 2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/barrier.h b/arch/ia64/include/asm/barrier.h
> index 843ba435e43b..39ed6515415f 100644
> --- a/arch/ia64/include/asm/barrier.h
> +++ b/arch/ia64/include/asm/barrier.h
> @@ -77,7 +77,7 @@ do {									\
>  	___p1;								\
>  })
>  
> -#define smp_store_mb(var, value)	do { WRITE_ONCE(var, value); mb(); } while (0)
> +#define smp_store_mb(var, value)	do { WRITE_ONCE(var, value); smp_mb(); } while (0)
>  
>  /*
>   * The group barrier in front of the rsm & ssm are necessary to ensure
> diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h
> index 51ccc7232042..5525268f35c0 100644
> --- a/arch/powerpc/include/asm/barrier.h
> +++ b/arch/powerpc/include/asm/barrier.h
> @@ -34,7 +34,7 @@
>  #define rmb()  __asm__ __volatile__ ("sync" : : : "memory")
>  #define wmb()  __asm__ __volatile__ ("sync" : : : "memory")
>  
> -#define smp_store_mb(var, value)	do { WRITE_ONCE(var, value); mb(); } while (0)
> +#define smp_store_mb(var, value)	do { WRITE_ONCE(var, value); smp_mb(); } while (0)
>  
>  #ifdef __SUBARCH_HAS_LWSYNC
>  #    define SMPWMB      LWSYNC
> diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
> index e6f8615a11eb..a4dea6050c77 100644
> --- a/arch/s390/include/asm/barrier.h
> +++ b/arch/s390/include/asm/barrier.h
> @@ -36,7 +36,7 @@
>  #define smp_mb__before_atomic()		smp_mb()
>  #define smp_mb__after_atomic()		smp_mb()
>  
> -#define smp_store_mb(var, value)		do { WRITE_ONCE(var, value); mb(); } while (0)
> +#define smp_store_mb(var, value)		do { WRITE_ONCE(var, value); smp_mb(); } while (0)
>  
>  #define smp_store_release(p, v)						\
>  do {									\
> diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
> index e6a83d712ef6..d716aa564931 100644
> --- a/include/asm-generic/barrier.h
> +++ b/include/asm-generic/barrier.h
> @@ -67,7 +67,7 @@
>  #endif
>  
>  #ifndef smp_store_mb
> -#define smp_store_mb(var, value)  do { WRITE_ONCE(var, value); mb(); } while (0)
> +#define smp_store_mb(var, value)  do { WRITE_ONCE(var, value); smp_mb(); } while (0)
>  #endif
>  
>  #ifndef smp_mb__before_atomic
> --
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