[RFC 2/7] vhost: Add kthread support in function vhost_worker_queue()

[Cindy Lu]

Added back the previously removed function vhost_worker_queue() and
renamed it to vhost_worker_queue_khtread(). The new vhost_worker_queue()
will select the different mode based on the value of the parameter.

Signed-off-by: Cindy Lu <l...@redhat.com>
---
 drivers/vhost/vhost.c | 30 ++++++++++++++++++++++++++++--
 drivers/vhost/vhost.h |  1 +
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index da701f6b3f2c..6261c9df468e 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -236,8 +236,8 @@ void vhost_poll_stop(struct vhost_poll *poll)
 }
 EXPORT_SYMBOL_GPL(vhost_poll_stop);
 
-static void vhost_worker_queue(struct vhost_worker *worker,
-                              struct vhost_work *work)
+static void vhost_worker_queue_task(struct vhost_worker *worker,
+                                   struct vhost_work *work)
 {
        if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
                /* We can only add the work to the list after we're
@@ -249,6 +249,32 @@ static void vhost_worker_queue(struct vhost_worker *worker,
        }
 }
 
+static void vhost_work_queue_kthread(struct vhost_worker *worker,
+                                    struct vhost_work *work)
+{
+       if (!worker)
+               return;
+
+       if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
+               /* We can only add the work to the list after we're
+                * sure it was not in the list.
+                * test_and_set_bit() implies a memory barrier.
+                */
+               llist_add(&work->node, &worker->work_list);
+
+               wake_up_process(worker->task);
+       }
+}
+
+static void vhost_worker_queue(struct vhost_worker *worker,
+                              struct vhost_work *work)
+{
+       if (use_kthread) {
+               vhost_work_queue_kthread(worker, work);
+       } else {
+               vhost_worker_queue_task(worker, work);
+       }
+}
 bool vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
 {
        struct vhost_worker *worker;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index bb75a292d50c..c7f126fd09e8 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -27,6 +27,7 @@ struct vhost_work {
 };
 
 struct vhost_worker {
+       struct task_struct      *task;
        struct vhost_task       *vtsk;
        struct vhost_dev        *dev;
        /* Used to serialize device wide flushing with worker swapping. */
-- 
2.45.0