From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 15B521A0F9D for ; Fri, 1 Jan 2016 06:09:56 +1100 (AEDT) Date: Thu, 31 Dec 2015 21:09:47 +0200 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Arnd Bergmann , linux-arch@vger.kernel.org, Andrew Cooper , virtualization@lists.linux-foundation.org, Stefano Stabellini , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , David Miller , 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.xenproject.org, Ingo Molnar Subject: [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Message-ID: <1451572003-2440-32-git-send-email-mst@redhat.com> References: <1451572003-2440-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1451572003-2440-1-git-send-email-mst@redhat.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , At the moment, xchg on sh only supports 4 and 1 byte values, so using it from smp_store_mb means attempts to store a 2 byte value using this macro fail. And happens to be exactly what virtio drivers want to do. Check size and fall back to a slower, but safe, WRITE_ONCE+smp_mb. Signed-off-by: Michael S. Tsirkin --- arch/sh/include/asm/barrier.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/sh/include/asm/barrier.h b/arch/sh/include/asm/barrier.h index f887c64..0cc5735 100644 --- a/arch/sh/include/asm/barrier.h +++ b/arch/sh/include/asm/barrier.h @@ -32,7 +32,15 @@ #define ctrl_barrier() __asm__ __volatile__ ("nop;nop;nop;nop;nop;nop;nop;nop") #endif -#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0) +#define __smp_store_mb(var, value) do { \ + if (sizeof(var) != 4 && sizeof(var) != 1) { \ + WRITE_ONCE(var, value); \ + __smp_mb(); \ + } else { \ + (void)xchg(&var, value); \ + } \ +} while (0) + #define smp_store_mb(var, value) __smp_store_mb(var, value) #include -- MST