2 files changed, 18 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);
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index de1b26aa5720..d1264e9a50a8 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -124,6 +124,13 @@ static void poll_napi(struct netpoll *np)
         if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) &&
             npinfo->poll_owner != smp_processor_id() &&
             spin_trylock(&npinfo->poll_lock)) {
+                /* When calling dev->poll from poll_napi, we may end up in
+                 * netif_rx_complete. However, only the CPU to which the
+                 * device was queued is allowed to remove it from poll_list.
+                 * Setting POLL_LIST_FROZEN tells netif_rx_complete
+                 * to leave the NAPI state alone.
+                 */
+                set_bit(__LINK_STATE_POLL_LIST_FROZEN, &np->dev->state);
                 npinfo->rx_flags |= NETPOLL_RX_DROP;
                 atomic_inc(&trapped);
 
@@ -131,6 +138,7 @@ static void poll_napi(struct netpoll *np)
 
                 atomic_dec(&trapped);
                 npinfo->rx_flags &= ~NETPOLL_RX_DROP;
+                clear_bit(__LINK_STATE_POLL_LIST_FROZEN, &np->dev->state);
                 spin_unlock(&npinfo->poll_lock);
         }
 }