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Commit a77a57a1 authored by Roland Dreier's avatar Roland Dreier
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IPoIB: Fix deadlock on RTNL in ipoib_stop() 

Commit c8c2afe3 ("IPoIB: Use rtnl lock/unlock when changing device
flags") added a call to rtnl_lock() in ipoib_mcast_join_task(), which
is run from the ipoib_workqueue.  However, ipoib_stop() (which is run
inside rtnl_lock()) flushes this workqueue, which leads to a deadlock
if the join task is pending.

Fix this by simply not flushing the workqueue from ipoib_stop().  It
turns out that we really don't care about workqueue tasks running
during or after ipoib_stop(), as long as we make sure to flush the
workqueue before unregistering a netdev.

This fixes <https://bugs.openfabrics.org/show_bug.cgi?id=1114

>.

Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
parent ffaa5b98

drivers/infiniband/ulp/ipoib/ipoib_main.c

+9 −10
Original line number Diff line number Diff line
@@ -156,14 +156,8 @@ static int ipoib_stop(struct net_device *dev) 


	netif_stop_queue(dev);



	/*

	 * Now flush workqueue to make sure a scheduled task doesn't

	 * bring our internal state back up.

	 */

	flush_workqueue(ipoib_workqueue);



	ipoib_ib_dev_down(dev, 1);

	ipoib_ib_dev_stop(dev, 1);

	ipoib_ib_dev_down(dev, 0);

	ipoib_ib_dev_stop(dev, 0);



	if (!test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags)) {

		struct ipoib_dev_priv *cpriv;
@@ -1314,7 +1308,7 @@ static struct net_device *ipoib_add_port(const char *format, 


register_failed:

	ib_unregister_event_handler(&priv->event_handler);

	flush_scheduled_work();

	flush_workqueue(ipoib_workqueue);



event_failed:

	ipoib_dev_cleanup(priv->dev);
@@ -1373,7 +1367,12 @@ static void ipoib_remove_one(struct ib_device *device) 


	list_for_each_entry_safe(priv, tmp, dev_list, list) {

		ib_unregister_event_handler(&priv->event_handler);

		flush_scheduled_work();



		rtnl_lock();

		dev_change_flags(priv->dev, priv->dev->flags & ~IFF_UP);

		rtnl_unlock();



		flush_workqueue(ipoib_workqueue);



		unregister_netdev(priv->dev);

		ipoib_dev_cleanup(priv->dev);

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

+9 −1
Original line number Diff line number Diff line
@@ -392,8 +392,16 @@ static int ipoib_mcast_join_complete(int status, 
					   &priv->mcast_task, 0);

		mutex_unlock(&mcast_mutex);



		if (mcast == priv->broadcast)

		if (mcast == priv->broadcast) {

			/*

			 * Take RTNL lock here to avoid racing with

			 * ipoib_stop() and turning the carrier back

			 * on while a device is being removed.

			 */

			rtnl_lock();

			netif_carrier_on(dev);

			rtnl_unlock();

		}



		return 0;

	}