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From:   Wenliang Wang <wangwenliang.1995@bytedance.com>
To:     mst@redhat.com, jasowang@redhat.com, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com
Cc:     virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Wenliang Wang <wangwenliang.1995@bytedance.com>
Subject: [PATCH v2] virtio_net: suppress cpu stall when free_unused_bufs
Date:   Fri, 28 Apr 2023 10:26:13 +0800
Message-Id: <20230428022613.863298-1-wangwenliang.1995@bytedance.com>
MIME-Version: 1.0
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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@bytedance.com>
---
v2:
-add need_resched check.
-apply same logic to sq.
---
 drivers/net/virtio_net.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ea1bd4bb326d..573558b69a60 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3559,12 +3559,16 @@ 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);
+		if (need_resched())
+			schedule();
 	}
 
 	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);
+		if (need_resched())
+			schedule();
 	}
 }
 
-- 
2.20.1