[NET]: neigh_stat preempt fix

On some code paths this code is playing with per-cpu data with preemption
enabled.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/neighbour.h

@@ -112,7 +112,11 @@ struct neigh_statistics
 };
 
 #define NEIGH_CACHE_STAT_INC(tbl, field)				\
-		(per_cpu_ptr((tbl)->stats, smp_processor_id())->field++)
+	do {								\
+		preempt_disable();					\
+		(per_cpu_ptr((tbl)->stats, smp_processor_id())->field)++; \
+		preempt_enable();					\
+	} while (0)
 
 struct neighbour
 {