[PATCH 3.4 157/214] drivers: hv: switch to use mb() instead of smp_mb()

[Greg Kroah-Hartman]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@xxxxxxxxxx>

commit 35848f68b07df3f917cb13fc3c134718669f569b upstream.

Even if guest were compiled without SMP support, it could not assume that host
wasn't. So switch to use mb() instead of smp_mb() to force memory barriers for
UP guest.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
 - Drop changes to functions that don't exist here
 - hv_ringbuffer_write() has only a write memory barrier]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
[hq: Backported to 3.4:
 - Add the change in hv_ringbuffer_read]
Signed-off-by: Qiang Huang <h.huangqiang@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/hv/ring_buffer.c |    4 ++--
 drivers/hv/vmbus_drv.c   |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -383,7 +383,7 @@ int hv_ringbuffer_write(struct hv_ring_b
 					     sizeof(u64));
 
 	/* Make sure we flush all writes before updating the writeIndex */
-	smp_wmb();
+	wmb();
 
 	/* Now, update the write location */
 	hv_set_next_write_location(outring_info, next_write_location);
@@ -485,7 +485,7 @@ int hv_ringbuffer_read(struct hv_ring_bu
 	/* Make sure all reads are done before we update the read index since */
 	/* the writer may start writing to the read area once the read index */
 	/*is updated */
-	smp_mb();
+	mb();
 
 	/* Update the read index */
 	hv_set_next_read_location(inring_info, next_read_location);
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -466,7 +466,7 @@ static void vmbus_on_msg_dpc(unsigned lo
 		 * will not deliver any more messages since there is
 		 * no empty slot
 		 */
-		smp_mb();
+		mb();
 
 		if (msg->header.message_flags.msg_pending) {
 			/*


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