[NET]: Fix races in net_rx_action vs netpoll.

Keep netpoll/poll_napi from messing with the poll_list.
Only net_rx_action is allowed to manipulate the list.

Signed-off-by: Olaf Kirch <olaf.kirch@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8590d685d935..79cc3dab4be7 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -261,6 +261,8 @@ enum netdev_state_t
         __LINK_STATE_LINKWATCH_PENDING,
         __LINK_STATE_DORMANT,
         __LINK_STATE_QDISC_RUNNING,
+        /* Set by the netpoll NAPI code */
+        __LINK_STATE_POLL_LIST_FROZEN,
 };
 
 
@@ -1014,6 +1016,14 @@ static inline void netif_rx_complete(struct net_device *dev)
 {
         unsigned long flags;
 
+#ifdef CONFIG_NETPOLL
+        /* Prevent race with netpoll - yes, this is a kludge.
+         * But at least it doesn't penalize the non-netpoll
+         * code path. */
+        if (test_bit(__LINK_STATE_POLL_LIST_FROZEN, &dev->state))
+                return;
+#endif
+
         local_irq_save(flags);
         __netif_rx_complete(dev);
         local_irq_restore(flags);