[1/3] [NEIGH] Print stack trace in neigh_add_timer

[Herbert Xu <herbert@gondor.apana.org.au>]

[NEIGH] Print stack trace in neigh_add_timer

Stack traces are very helpful in determining the exact nature of a bug.
So let's print a stack trace when the timer is added twice.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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diff --git a/net/core/neighbour.c b/net/core/neighbour.c
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -732,6 +732,7 @@ static inline void neigh_add_timer(struc
 	if (unlikely(mod_timer(&n->timer, when))) {
 		printk("NEIGH: BUG, double timer add, state is %x\n",
 		       n->nud_state);
+		dump_stack();
 	}
 }