linux-kernel - Re: [PATCH v3 05/41] powerpc: reuse asm-generic/barrier.h

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Date:	Tue, 12 Jan 2016 08:31:02 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	virtualization@...ts.linux-foundation.org,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Joe Perches <joe@...ches.com>,
	David Miller <davem@...emloft.net>, linux-ia64@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-metag@...r.kernel.org, linux-mips@...ux-mips.org,
	x86@...nel.org, user-mode-linux-devel@...ts.sourceforge.net,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	xen-devel@...ts.xenproject.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Ingo Molnar <mingo@...nel.org>,
	Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH v3 05/41] powerpc: reuse asm-generic/barrier.h

On Sun, Jan 10, 2016 at 04:17:09PM +0200, Michael S. Tsirkin wrote:
> On powerpc read_barrier_depends, smp_read_barrier_depends
> smp_store_mb(), smp_mb__before_atomic and smp_mb__after_atomic match the
> asm-generic variants exactly. Drop the local definitions and pull in
> asm-generic/barrier.h instead.
> 
> This is in preparation to refactoring this code area.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> Acked-by: Arnd Bergmann <arnd@...db.de>

Looks sane to me.

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  arch/powerpc/include/asm/barrier.h | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h
> index a7af5fb..980ad0c 100644
> --- a/arch/powerpc/include/asm/barrier.h
> +++ b/arch/powerpc/include/asm/barrier.h
> @@ -34,8 +34,6 @@
>  #define rmb()  __asm__ __volatile__ ("sync" : : : "memory")
>  #define wmb()  __asm__ __volatile__ ("sync" : : : "memory")
> 
> -#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
> -
>  #ifdef __SUBARCH_HAS_LWSYNC
>  #    define SMPWMB      LWSYNC
>  #else
> @@ -60,9 +58,6 @@
>  #define smp_wmb()	barrier()
>  #endif /* CONFIG_SMP */
> 
> -#define read_barrier_depends()		do { } while (0)
> -#define smp_read_barrier_depends()	do { } while (0)
> -
>  /*
>   * This is a barrier which prevents following instructions from being
>   * started until the value of the argument x is known.  For example, if
> @@ -87,8 +82,8 @@ do {									\
>  	___p1;								\
>  })
> 
> -#define smp_mb__before_atomic()     smp_mb()
> -#define smp_mb__after_atomic()      smp_mb()
>  #define smp_mb__before_spinlock()   smp_mb()
> 
> +#include <asm-generic/barrier.h>
> +
>  #endif /* _ASM_POWERPC_BARRIER_H */
> -- 
> MST
>