linux-kernel - [PATCH 2/3] vringh: kill off ACCESS

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Date:   Thu, 24 Nov 2016 10:25:13 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org
Cc:     dave@...olabs.net, dbueso@...e.de, dvyukov@...gle.com,
        jasowang@...hat.com, kvm@...r.kernel.org, mark.rutland@....com,
        mst@...hat.com, netdev@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH 2/3] vringh: kill off ACCESS_ONCE()

Despite living under drivers/ vringh.c is also used as part of the userspace
virtio tools. Before we can kill off the ACCESS_ONCE()definition in the tools,
we must convert vringh.c to use {READ,WRITE}_ONCE().

This patch does so, along with the required include of <linux/compiler.h> for
the relevant definitions. The userspace tools provide their own definitions in
their own <linux/compiler.h>.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Jason Wang <jasowang@...hat.com>
Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: netdev@...r.kernel.org
Cc: virtualization@...ts.linux-foundation.org
---
 drivers/vhost/vringh.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 3bb02c6..bb8971f 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -3,6 +3,7 @@
  *
  * Since these may be in userspace, we use (inline) accessors.
  */
+#include <linux/compiler.h>
 #include <linux/module.h>
 #include <linux/vringh.h>
 #include <linux/virtio_ring.h>
@@ -820,13 +821,13 @@ EXPORT_SYMBOL(vringh_need_notify_user);
 static inline int getu16_kern(const struct vringh *vrh,
 			      u16 *val, const __virtio16 *p)
 {
-	*val = vringh16_to_cpu(vrh, ACCESS_ONCE(*p));
+	*val = vringh16_to_cpu(vrh, READ_ONCE(*p));
 	return 0;
 }
 
 static inline int putu16_kern(const struct vringh *vrh, __virtio16 *p, u16 val)
 {
-	ACCESS_ONCE(*p) = cpu_to_vringh16(vrh, val);
+	WRITE_ONCE(*p, cpu_to_vringh16(vrh, val));
 	return 0;
 }
 
-- 
2.7.4