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

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-arch@vger.kernel.org,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	virtualization@lists.linux-foundation.org,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	"H. Peter Anvin" <hpa@zytor.com>, Joe Perches <joe@perches.com>,
	David Miller <davem@davemloft.net>,
	linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-metag@vger.kernel.org, linux-mips@linux-mips.org,
	x86@kernel.org, user-mode-linux-devel@lists.sourceforge.net,
	adi-buildroot-devel@lists.sourceforge.net,
	linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	xen-devel@lists.xenpr
Subject: Re: [PATCH v3 01/41] lcoking/barriers, arch: Use smp barriers in smp_store_release()
Date: Tue, 12 Jan 2016 16:28:44 +0000	[thread overview]
Message-ID: <20160112162844.GD3818@linux.vnet.ibm.com> (raw)
In-Reply-To: <1452426622-4471-2-git-send-email-mst@redhat.com>

On Sun, Jan 10, 2016 at 04:16:32PM +0200, Michael S. Tsirkin wrote:
> From: Davidlohr Bueso <dave@stgolabs.net>
> 
> 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@suse.de>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: <linux-arch@vger.kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: dave@stgolabs.net
> Link: http://lkml.kernel.org/r/1445975631-17047-3-git-send-email-dave@stgolabs.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>

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

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

> ---
>  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
> 