linux-kernel - Re: [PATCH net v3] virtio-net: fix recursived rtnl

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Message-ID: <20250716092717-mutt-send-email-mst@kernel.org>
Date: Wed, 16 Jul 2025 09:27:24 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Zigit Zo <zuozhijie@...edance.com>
Cc: jasowang@...hat.com, xuanzhuo@...ux.alibaba.com, eperezma@...hat.com,
	virtualization@...ts.linux.dev, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kuba@...nel.org, pabeni@...hat.com,
	andrew+netdev@...n.ch, edumazet@...gle.com
Subject: Re: [PATCH net v3] virtio-net: fix recursived rtnl_lock() during
 probe()

On Wed, Jul 16, 2025 at 07:57:17PM +0800, Zigit Zo wrote:
> The deadlock appears in a stack trace like:
> 
>   virtnet_probe()
>     rtnl_lock()
>     virtio_config_changed_work()
>       netdev_notify_peers()
>         rtnl_lock()
> 
> It happens if the VMM sends a VIRTIO_NET_S_ANNOUNCE request while the
> virtio-net driver is still probing.
> 
> The config_work in probe() will get scheduled until virtnet_open() enables
> the config change notification via virtio_config_driver_enable().
> 
> Fixes: df28de7b0050 ("virtio-net: synchronize operstate with admin state on up/down")
> Signed-off-by: Zigit Zo <zuozhijie@...edance.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
> v3 -> v2:
> * Simplify the changes.
> v1 -> v2:
> * Check vi->status in virtnet_open().
> * https://lore.kernel.org/netdev/20250702103722.576219-1-zuozhijie@bytedance.com/
> v1:
> * https://lore.kernel.org/netdev/20250630095109.214013-1-zuozhijie@bytedance.com/
> ---
>  drivers/net/virtio_net.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 5d674eb9a0f2..82b4a2a2b8c4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -7059,7 +7059,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	   otherwise get link status from config. */
>  	netif_carrier_off(dev);
>  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
> -		virtnet_config_changed_work(&vi->config_work);
> +		virtio_config_changed(vi->vdev);
>  	} else {
>  		vi->status = VIRTIO_NET_S_LINK_UP;
>  		virtnet_update_settings(vi);
> 
> base-commit: dae7f9cbd1909de2b0bccc30afef95c23f93e477
> -- 
> 2.49.0