Re: [Xen-devel] [PATCH v3 01/41] lcoking/barriers, arch: Use smp barriers in smp_store_release()

["Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>]

On Sun, Jan 10, 2016 at 04:16:32PM +0200, Michael S. Tsirkin wrote:
> From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> 
> With commit b92b8b35a2e ("locking/arch: Rename set_mb() to smp_store_mb()")
> it was made clear that the context of this call (and thus set_mb)
> is strictly for CPU ordering, as opposed to IO. As such all archs
> should use the smp variant of mb(), respecting the semantics and
> saving a mandatory barrier on UP.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: <linux-arch@xxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Cc: dave@xxxxxxxxxxxx
> Link: 
> http://lkml.kernel.org/r/1445975631-17047-3-git-send-email-dave@xxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>

Aside from a need for s/lcoking/locking/ in the subject line:

Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>

> ---
>  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 df896a1..209c4b8 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 0eca6ef..a7af5fb 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 d68e11e..7ffd0b1 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 b42afad..0f45f93 100644
> --- a/include/asm-generic/barrier.h
> +++ b/include/asm-generic/barrier.h
> @@ -93,7 +93,7 @@
>  #endif       /* CONFIG_SMP */
> 
>  #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
> -- 
> MST
> 


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