[PATCH v3] virtio_net: suppress cpu stall when free_unused_bufs

[Wenliang Wang]

For multi-queue and large ring-size use case, the following error
occurred when free_unused_bufs:
rcu: INFO: rcu_sched self-detected stall on CPU.

Signed-off-by: Wenliang Wang <wangwenliang.1995@xxxxxxxxxxxxx>
---
v2:
-add need_resched check.
-apply same logic to sq.
v3:
-use cond_resched instead.
---
 drivers/net/virtio_net.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ea1bd4bb326d..744bdc8a1abd 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3559,12 +3559,14 @@ static void free_unused_bufs(struct virtnet_info *vi)
 		struct virtqueue *vq = vi->sq[i].vq;
 		while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
 			virtnet_sq_free_unused_buf(vq, buf);
+		cond_resched();
 	}
 
 	for (i = 0; i < vi->max_queue_pairs; i++) {
 		struct virtqueue *vq = vi->rq[i].vq;
 		while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
 			virtnet_rq_free_unused_buf(vq, buf);
+		cond_resched();
 	}
 }
 
-- 
2.20.1