Commit 4f8544dd authored by Reinhard Speyerer's avatar Reinhard Speyerer Committed by Greg Kroah-Hartman

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 <>
Signed-off-by: default avatarReinhard Speyerer <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarSasha Levin <>
parent 0d34ea83
......@@ -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_queue(dev, head);
/* Get rid of the reference to 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, NULL);
if (!qmimux_has_slaves(dev))
info->flags &= ~QMI_WWAN_FLAG_MUX;
......@@ -1423,6 +1424,7 @@ static void qmi_wwan_disconnect(struct usb_interface *intf)
struct qmi_wwan_state *info;
struct list_head *iter;
struct net_device *ldev;
/* called twice if separate control and data intf */
if (!dev)
......@@ -1435,8 +1437,9 @@ static void qmi_wwan_disconnect(struct usb_interface *intf)
netdev_for_each_upper_dev_rcu(dev->net, ldev, iter)
qmimux_unregister_device(ldev, &list);
info->flags &= ~QMI_WWAN_FLAG_MUX;
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