[PATCH v4 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.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 63 ++++++++++++++++--------------
 1 file changed, 33 insertions(+), 30 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index eff104f90cee..0f15575df394 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -501,44 +501,47 @@ 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];
+
+			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];
 
-		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,
-- 
2.54.0