[PATCH] IPoIB: Fix device removal race

Currently we may have work scheduled in default kernel workqueue when
the device is going down.  The device could get freed before this
workqueue gets serviced.  I am actually seeing this causing system
hangs.

The following patch fixes this by using ipoib_workqueue which gets
flushed when the device is going down.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 57c3ac9..0e8ac13 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -672,7 +672,7 @@
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 
-	schedule_work(&priv->restart_task);
+	queue_work(ipoib_workqueue, &priv->restart_task);
 }
 
 static void ipoib_neigh_destructor(struct neighbour *n)