[PATCH v5 1/2] vduse: do not take rwsem at reset work flush

["Eugenio Pérez" <eperezma@redhat.com>]

Next patches need to check suspend flag at this work item, and the
rwlock is used to protect the suspend flag update.  If the work takes
the rwlock too it will produce a deadlock.

Make flushing work do nothing when called by de-initializing everything:
vq->ready, vq->kickfd, vq->cb.callback.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 67 ++++++++++++++++--------------
 1 file changed, 35 insertions(+), 32 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 307d13fbe942..347afe7c6d92 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -503,46 +503,49 @@ static void vduse_dev_reset(struct vduse_dev *dev)
 			vduse_domain_reset_bounce_map(domain);
 	}
 
-	down_write(&dev->rwsem);
+	scoped_guard(rwsem_write, &dev->rwsem) {
+		dev->status = 0;
+		dev->driver_features = 0;
+		dev->generation++;
+		spin_lock(&dev->irq_lock);
+		dev->config_cb.callback = NULL;
+		dev->config_cb.private = NULL;
+		spin_unlock(&dev->irq_lock);
+
+		for (i = 0; i < dev->vq_num; i++) {
+			struct vduse_virtqueue *vq = dev->vqs[i];
+
+			scoped_guard(spinlock_bh, &vq->ready_lock) {
+				vq->ready = false;
+			}
+			vq->desc_addr = 0;
+			vq->driver_addr = 0;
+			vq->device_addr = 0;
+			vq->num = 0;
+			memset(&vq->state, 0, sizeof(vq->state));
+
+			spin_lock(&vq->kick_lock);
+			vq->kicked = false;
+			if (vq->kickfd)
+				eventfd_ctx_put(vq->kickfd);
+			vq->kickfd = NULL;
+			spin_unlock(&vq->kick_lock);
+
+			spin_lock(&vq->irq_lock);
+			vq->cb.callback = NULL;
+			vq->cb.private = NULL;
+			vq->cb.trigger = NULL;
+			spin_unlock(&vq->irq_lock);
+		}
+	}
 
-	dev->status = 0;
-	dev->driver_features = 0;
-	dev->generation++;
-	spin_lock(&dev->irq_lock);
-	dev->config_cb.callback = NULL;
-	dev->config_cb.private = NULL;
-	spin_unlock(&dev->irq_lock);
 	flush_work(&dev->inject);
-
 	for (i = 0; i < dev->vq_num; i++) {
 		struct vduse_virtqueue *vq = dev->vqs[i];
 
-		scoped_guard(spinlock_bh, &vq->ready_lock) {
-			vq->ready = false;
-		}
-		vq->desc_addr = 0;
-		vq->driver_addr = 0;
-		vq->device_addr = 0;
-		vq->num = 0;
-		memset(&vq->state, 0, sizeof(vq->state));
-
-		spin_lock(&vq->kick_lock);
-		vq->kicked = false;
-		if (vq->kickfd)
-			eventfd_ctx_put(vq->kickfd);
-		vq->kickfd = NULL;
-		spin_unlock(&vq->kick_lock);
-
-		spin_lock(&vq->irq_lock);
-		vq->cb.callback = NULL;
-		vq->cb.private = NULL;
-		vq->cb.trigger = NULL;
-		spin_unlock(&vq->irq_lock);
 		flush_work(&vq->inject);
 		flush_work(&vq->kick);
 	}
-
-	up_write(&dev->rwsem);
 }
 
 static int vduse_vdpa_set_vq_address(struct vdpa_device *vdpa, u16 idx,
-- 
2.55.0