From patchwork Sun May 23 15:56:05 2010
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
X-Patchwork-Submitter: "Michael S. Tsirkin" <mst@redhat.com>
X-Patchwork-Id: 101743
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by demeter.kernel.org (8.14.3/8.14.3) with ESMTP id o4NG1KPQ018566
	for <patchwork-kvm@patchwork.kernel.org>;
	Sun, 23 May 2010 16:01:21 GMT
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752921Ab0EWQA4 (ORCPT
	<rfc822;patchwork-kvm@patchwork.kernel.org>);
	Sun, 23 May 2010 12:00:56 -0400
Received: from mx1.redhat.com ([209.132.183.28]:12337 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1752581Ab0EWQAz (ORCPT <rfc822;kvm@vger.kernel.org>);
	Sun, 23 May 2010 12:00:55 -0400
Received: from int-mx05.intmail.prod.int.phx2.redhat.com
	(int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18])
	by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o4NG0IKw020609
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK);
	Sun, 23 May 2010 12:00:18 -0400
Received: from redhat.com (vpn1-7-182.ams2.redhat.com [10.36.7.182])
	by int-mx05.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with
	SMTP id o4NG0ETx027565; Sun, 23 May 2010 12:00:15 -0400
Date: Sun, 23 May 2010 18:56:05 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Avi Kivity <avi@redhat.com>, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH RFC] virtio: put last seen used index into
	ring itself
Message-ID: <20100523155605.GB14733@redhat.com>
References: <20100505205814.GA7090@redhat.com> <4BF39C12.7090407@redhat.com>
	<201005201431.51142.rusty@rustcorp.com.au>
	<201005201438.17010.rusty@rustcorp.com.au>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <201005201438.17010.rusty@rustcorp.com.au>
User-Agent: Mutt/1.5.19 (2009-01-05)
X-Scanned-By: MIMEDefang 2.67 on 10.5.11.18
Sender: kvm-owner@vger.kernel.org
Precedence: bulk
List-ID: <kvm.vger.kernel.org>
X-Mailing-List: kvm@vger.kernel.org
X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by
	milter-greylist-4.2.3 (demeter.kernel.org [140.211.167.41]);
	Sun, 23 May 2010 16:01:21 +0000 (UTC)


diff --git a/cachebounce.c b/cachebounce.c
index 0387027..ebe5a37 100644
--- a/cachebounce.c
+++ b/cachebounce.c
@@ -77,6 +77,7 @@ int main(int argc, char *argv[])
 				count++;
 				counter->cacheline1 = count;
 				count++;
+				__sync_synchronize();
 			}
 			break;
 		case UNSHARE:
@@ -86,6 +87,7 @@ int main(int argc, char *argv[])
 				count++;
 				counter->cacheline2 = count;
 				count++;
+				__sync_synchronize();
 			}
 			break;
 		case LOCKSHARE:
@@ -98,6 +100,7 @@ int main(int argc, char *argv[])
 			break;
 		case LOCKUNSHARE:
 			while (count < MAX_BOUNCES) {
+				__sync_synchronize();
 				/* Spin waiting for other side to change it. */
 				while (counter->cacheline1 != count);
 				__sync_val_compare_and_swap(&counter->cacheline2, count, count+1);
@@ -115,6 +118,7 @@ int main(int argc, char *argv[])
 				count++;
 				counter->cacheline1 = count;
 				count++;
+				__sync_synchronize();
 			}
 			break;
 		case UNSHARE:
@@ -124,6 +128,7 @@ int main(int argc, char *argv[])
 				count++;
 				counter->cacheline1 = count;
 				count++;
+				__sync_synchronize();
 			}
 			break;
 		case LOCKSHARE: