Some drivers with shared NAPI need a synchronization barrier.
Also suggested by Benjamin Herrenschmidt for EMAC.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>

--- a/include/linux/netdevice.h	2007-10-17 08:45:32.000000000 -0700
+++ b/include/linux/netdevice.h	2007-10-17 08:47:54.000000000 -0700
@@ -407,6 +407,24 @@ static inline void napi_enable(struct na
 	clear_bit(NAPI_STATE_SCHED, &n->state);
 }
 
+#ifdef CONFIG_SMP
+/**
+ *	napi_synchronize - wait until NAPI is not running
+ *	@n: napi context
+ *
+ * Wait until NAPI is done being scheduled on this context.
+ * Waits till any outstanding processing completes but
+ * does not disable future activations.
+ */
+static inline void napi_synchronize(const struct napi_struct *n)
+{
+	while (test_bit(NAPI_STATE_SCHED, &n->state))
+		msleep(1);
+}
+#else
+# define napi_synchronize(n)	barrier()
+#endif
+
 /*
  *	The DEVICE structure.
  *	Actually, this whole structure is a big mistake.  It mixes I/O

-- 
Stephen Hemminger <shemminger@linux-foundation.org>

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