From b8de77cd2a205cb64bfb835f2789bee06af43db6 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 12 Jan 2012 15:44:43 +1030
Subject: [PATCH] --- yaml --- r: 284239 b: refs/heads/master c:
 41f0377f73039ca6fe97a469d1941a89cd9757f1 h: refs/heads/master i:   284237:
 3169824d2355c97a98236b445aeb90c10568818d   284235:
 4582e9ecb0f22412a87c419af5d7ed136110d4a6   284231:
 26dbddca5c3232cab7a1c4bb48cd32297f90df03   284223:
 6a08649ccedcfcb6bbd2c2958d76e1ebdf7eef04 v: v3

---
 [refs]                             |  2 +-
 trunk/drivers/virtio/virtio_ring.c | 60 ++++++++++++++++++++++++------
 trunk/include/linux/virtio.h       |  4 ++
 3 files changed, 53 insertions(+), 13 deletions(-)

diff --git a/[refs] b/[refs]
index cdc0743473f3..0df3b3b0bb91 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f96fde41f7f9af6cf20f6a1919f5d9670f84d574
+refs/heads/master: 41f0377f73039ca6fe97a469d1941a89cd9757f1
diff --git a/trunk/drivers/virtio/virtio_ring.c b/trunk/drivers/virtio/virtio_ring.c
index 6ea92a6d1134..c56bbe799241 100644
--- a/trunk/drivers/virtio/virtio_ring.c
+++ b/trunk/drivers/virtio/virtio_ring.c
@@ -262,19 +262,22 @@ int virtqueue_add_buf(struct virtqueue *_vq,
 EXPORT_SYMBOL_GPL(virtqueue_add_buf);
 
 /**
- * virtqueue_kick - update after add_buf
+ * virtqueue_kick_prepare - first half of split virtqueue_kick call.
  * @vq: the struct virtqueue
  *
- * After one or more virtqueue_add_buf calls, invoke this to kick
- * the other side.
+ * Instead of virtqueue_kick(), you can do:
+ *	if (virtqueue_kick_prepare(vq))
+ *		virtqueue_notify(vq);
  *
- * Caller must ensure we don't call this with other virtqueue
- * operations at the same time (except where noted).
+ * This is sometimes useful because the virtqueue_kick_prepare() needs
+ * to be serialized, but the actual virtqueue_notify() call does not.
  */
-void virtqueue_kick(struct virtqueue *_vq)
+bool virtqueue_kick_prepare(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	u16 new, old;
+	bool needs_kick;
+
 	START_USE(vq);
 	/* Descriptors and available array need to be set before we expose the
 	 * new available array entries. */
@@ -287,13 +290,46 @@ void virtqueue_kick(struct virtqueue *_vq)
 	/* Need to update avail index before checking if we should notify */
 	virtio_mb(vq);
 
-	if (vq->event ?
-	    vring_need_event(vring_avail_event(&vq->vring), new, old) :
-	    !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
-		/* Prod other side to tell it about changes. */
-		vq->notify(&vq->vq);
-
+	if (vq->event) {
+		needs_kick = vring_need_event(vring_avail_event(&vq->vring),
+					      new, old);
+	} else {
+		needs_kick = !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
+	}
 	END_USE(vq);
+	return needs_kick;
+}
+EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
+
+/**
+ * virtqueue_notify - second half of split virtqueue_kick call.
+ * @vq: the struct virtqueue
+ *
+ * This does not need to be serialized.
+ */
+void virtqueue_notify(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	/* Prod other side to tell it about changes. */
+	vq->notify(_vq);
+}
+EXPORT_SYMBOL_GPL(virtqueue_notify);
+
+/**
+ * virtqueue_kick - update after add_buf
+ * @vq: the struct virtqueue
+ *
+ * After one or more virtqueue_add_buf calls, invoke this to kick
+ * the other side.
+ *
+ * Caller must ensure we don't call this with other virtqueue
+ * operations at the same time (except where noted).
+ */
+void virtqueue_kick(struct virtqueue *vq)
+{
+	if (virtqueue_kick_prepare(vq))
+		virtqueue_notify(vq);
 }
 EXPORT_SYMBOL_GPL(virtqueue_kick);
 
diff --git a/trunk/include/linux/virtio.h b/trunk/include/linux/virtio.h
index ec1706e7df50..31fe3a62874b 100644
--- a/trunk/include/linux/virtio.h
+++ b/trunk/include/linux/virtio.h
@@ -34,6 +34,10 @@ int virtqueue_add_buf(struct virtqueue *vq,
 
 void virtqueue_kick(struct virtqueue *vq);
 
+bool virtqueue_kick_prepare(struct virtqueue *vq);
+
+void virtqueue_notify(struct virtqueue *vq);
+
 void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
 
 void virtqueue_disable_cb(struct virtqueue *vq);