From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <peterz@infradead.org>
Received: from bombadil.infradead.org (bombadil.infradead.org
 [IPv6:2001:1868:205::9])
 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id E83EB1A0045
 for <linuxppc-dev@lists.ozlabs.org>; Tue,  5 Jan 2016 00:41:43 +1100 (AEDT)
Date: Mon, 4 Jan 2016 14:41:28 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
 linux-arch@vger.kernel.org, Andrew Cooper <andrew.cooper3@citrix.com>,
 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>,
 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.xenproject.org,
 James Hogan <james.hogan@imgtec.com>,
 Ingo Molnar <mingo@kernel.org>, Davidlohr Bueso <dbueso@suse.de>,
 Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH v2 20/32] metag: define __smp_xxx
Message-ID: <20160104134128.GZ6344@twins.programming.kicks-ass.net>
References: <1451572003-2440-1-git-send-email-mst@redhat.com>
 <1451572003-2440-21-git-send-email-mst@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
In-Reply-To: <1451572003-2440-21-git-send-email-mst@redhat.com>
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>

On Thu, Dec 31, 2015 at 09:08:22PM +0200, Michael S. Tsirkin wrote:
> +#ifdef CONFIG_SMP
> +#define fence() metag_fence()
> +#else
> +#define fence()		do { } while (0)
>  #endif

James, it strikes me as odd that fence() is a no-op instead of a
barrier() for UP, can you verify/explain?