[NET] link_watch: Eliminate potential delay on wrap-around

When the jiffies wrap around or when the system boots up for the first
time, down events can be delayed indefinitely since we no longer
update linkwatch_nextevent when only urgent events are processed.

This patch fixes this by setting linkwatch_nextevent when a
wrap-around occurs.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/link_watch.c

@@ -101,8 +101,10 @@ static void linkwatch_schedule_work(unsigned long delay)
 		return;
 
 	/* If we wrap around we'll delay it by at most HZ. */
-	if (delay > HZ)
+	if (delay > HZ) {
+		linkwatch_nextevent = jiffies;
 		delay = 0;
+	}
 
 	schedule_delayed_work(&linkwatch_work, delay);
 }