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Commit dc84e983 authored by Reinhard Speyerer's avatar Reinhard Speyerer Committed by Greg Kroah-Hartman
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qmi_wwan: avoid RCU stalls on device disconnect when in QMAP mode 



[ Upstream commit a8fdde1cb830e560208af42b6c10750137f53eb3 ]

Switch qmimux_unregister_device() and qmi_wwan_disconnect() to
use unregister_netdevice_queue() and unregister_netdevice_many()
instead of unregister_netdevice(). This avoids RCU stalls which
have been observed on device disconnect in certain setups otherwise.

Fixes: c6adf779 ("net: usb: qmi_wwan: add qmap mux protocol support")
Cc: Daniele Palmas <dnlplm@gmail.com>
Signed-off-by: default avatarReinhard Speyerer <rspmn@arcor.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent dbc6a83c

drivers/net/usb/qmi_wwan.c

+7 −4
Original line number Diff line number Diff line
@@ -247,13 +247,14 @@ static int qmimux_register_device(struct net_device *real_dev, u8 mux_id) 
	return err;

}



static void qmimux_unregister_device(struct net_device *dev)

static void qmimux_unregister_device(struct net_device *dev,

				     struct list_head *head)

{

	struct qmimux_priv *priv = netdev_priv(dev);

	struct net_device *real_dev = priv->real_dev;



	netdev_upper_dev_unlink(real_dev, dev);

	unregister_netdevice(dev);

	unregister_netdevice_queue(dev, head);



	/* Get rid of the reference to real_dev */

	dev_put(real_dev);
@@ -424,7 +425,7 @@ static ssize_t del_mux_store(struct device *d, struct device_attribute *attr, c 
		ret = -EINVAL;

		goto err;

	}

	qmimux_unregister_device(del_dev);

	qmimux_unregister_device(del_dev, NULL);



	if (!qmimux_has_slaves(dev))

		info->flags &= ~QMI_WWAN_FLAG_MUX;
@@ -1434,6 +1435,7 @@ static void qmi_wwan_disconnect(struct usb_interface *intf) 
	struct qmi_wwan_state *info;

	struct list_head *iter;

	struct net_device *ldev;

	LIST_HEAD(list);



	/* called twice if separate control and data intf */

	if (!dev)
@@ -1446,8 +1448,9 @@ static void qmi_wwan_disconnect(struct usb_interface *intf) 
		}

		rcu_read_lock();

		netdev_for_each_upper_dev_rcu(dev->net, ldev, iter)

			qmimux_unregister_device(ldev);

			qmimux_unregister_device(ldev, &list);

		rcu_read_unlock();

		unregister_netdevice_many(&list);

		rtnl_unlock();

		info->flags &= ~QMI_WWAN_FLAG_MUX;

	}