sunvnet: Schedule maybe_tx_wakeup() as a tasklet from ldc_rx path

At the tail of vnet_event(), if we hit the maybe_tx_wakeup()
condition, we try to take the netif_tx_lock() in the
recv-interrupt-context and can deadlock with dev_watchdog().
vnet_event() should schedule maybe_tx_wakeup() as a tasklet
to avoid this deadlock

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 14 insertions, 2 deletions

diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
index a5871791e452..23c89ab5a6ad 100644
--- a/drivers/net/ethernet/sun/sunvnet.c
+++ b/drivers/net/ethernet/sun/sunvnet.c
@@ -488,8 +488,9 @@ static int handle_mcast(struct vnet_port *port, void *msgbuf)
         return 0;
 }
 
-static void maybe_tx_wakeup(struct vnet *vp)
+static void maybe_tx_wakeup(unsigned long param)
 {
+        struct vnet *vp = (struct vnet *)param;
         struct net_device *dev = vp->dev;
 
         netif_tx_lock(dev);
@@ -586,8 +587,13 @@ static void vnet_event(void *arg, int event)
                         break;
         }
         spin_unlock(&vio->lock);
+        /* Kick off a tasklet to wake the queue.  We cannot call
+         * maybe_tx_wakeup directly here because we could deadlock on
+         * netif_tx_lock() with dev_watchdog()
+         */
         if (unlikely(tx_wakeup && err != -ECONNRESET))
-                maybe_tx_wakeup(port->vp);
+                tasklet_schedule(&port->vp->vnet_tx_wakeup);
+
         local_irq_restore(flags);
 }
 
@@ -1070,6 +1076,7 @@ static struct vnet *vnet_new(const u64 *local_mac)
         vp = netdev_priv(dev);
 
         spin_lock_init(&vp->lock);
+        tasklet_init(&vp->vnet_tx_wakeup, maybe_tx_wakeup, (unsigned long)vp);
         vp->dev = dev;
 
         INIT_LIST_HEAD(&vp->port_list);
@@ -1129,6 +1136,7 @@ static void vnet_cleanup(void)
                 vp = list_first_entry(&vnet_list, struct vnet, list);
                 list_del(&vp->list);
                 dev = vp->dev;
+                tasklet_kill(&vp->vnet_tx_wakeup);
                 /* vio_unregister_driver() should have cleaned up port_list */
                 BUG_ON(!list_empty(&vp->port_list));
                 unregister_netdev(dev);
diff --git a/drivers/net/ethernet/sun/sunvnet.h b/drivers/net/ethernet/sun/sunvnet.h
index d347a5bf24b0..de5c2c64996f 100644
--- a/drivers/net/ethernet/sun/sunvnet.h
+++ b/drivers/net/ethernet/sun/sunvnet.h
@@ -1,6 +1,8 @@
 #ifndef _SUNVNET_H
 #define _SUNVNET_H
 
+#include <linux/interrupt.h>
+
 #define DESC_NCOOKIES(entry_size)       \
         ((entry_size) - sizeof(struct vio_net_desc))
 
@@ -78,6 +80,8 @@ struct vnet {
 
         struct list_head        list;
         u64                     local_mac;
+
+        struct tasklet_struct   vnet_tx_wakeup;
 };
 
 #endif /* _SUNVNET_H */