Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next

[cascardo/linux.git] / drivers / virtio / virtio_ring.c

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c702074..6b4a4db 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -576,19 +576,21 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
 EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
 
 /**
- * virtqueue_enable_cb - restart callbacks after disable_cb.
+ * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
  * @vq: the struct virtqueue we're talking about.
  *
- * This re-enables callbacks; it returns "false" if there are pending
- * buffers in the queue, to detect a possible race between the driver
- * checking for more work, and enabling callbacks.
+ * This re-enables callbacks; it returns current queue state
+ * in an opaque unsigned value. This value should be later tested by
+ * virtqueue_poll, to detect a possible race between the driver checking for
+ * more work, and enabling callbacks.
  *
  * Caller must ensure we don't call this with other virtqueue
  * operations at the same time (except where noted).
  */
-bool virtqueue_enable_cb(struct virtqueue *_vq)
+unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
 {
        struct vring_virtqueue *vq = to_vvq(_vq);
+       u16 last_used_idx;
 
        START_USE(vq);
 
@@ -598,15 +600,45 @@ bool virtqueue_enable_cb(struct virtqueue *_vq)
         * either clear the flags bit or point the event index at the next
         * entry. Always do both to keep code simple. */
        vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
-       vring_used_event(&vq->vring) = vq->last_used_idx;
+       vring_used_event(&vq->vring) = last_used_idx = vq->last_used_idx;
+       END_USE(vq);
+       return last_used_idx;
+}
+EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
+
+/**
+ * virtqueue_poll - query pending used buffers
+ * @vq: the struct virtqueue we're talking about.
+ * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
+ *
+ * Returns "true" if there are pending used buffers in the queue.
+ *
+ * This does not need to be serialized.
+ */
+bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
+{
+       struct vring_virtqueue *vq = to_vvq(_vq);
+
        virtio_mb(vq->weak_barriers);
-       if (unlikely(more_used(vq))) {
-               END_USE(vq);
-               return false;
-       }
+       return (u16)last_used_idx != vq->vring.used->idx;
+}
+EXPORT_SYMBOL_GPL(virtqueue_poll);
 
-       END_USE(vq);
-       return true;
+/**
+ * virtqueue_enable_cb - restart callbacks after disable_cb.
+ * @vq: the struct virtqueue we're talking about.
+ *
+ * This re-enables callbacks; it returns "false" if there are pending
+ * buffers in the queue, to detect a possible race between the driver
+ * checking for more work, and enabling callbacks.
+ *
+ * Caller must ensure we don't call this with other virtqueue
+ * operations at the same time (except where noted).
+ */
+bool virtqueue_enable_cb(struct virtqueue *_vq)
+{
+       unsigned last_used_idx = virtqueue_enable_cb_prepare(_vq);
+       return !virtqueue_poll(_vq, last_used_idx);
 }
 EXPORT_SYMBOL_GPL(virtqueue_enable_cb);