[NET] linkwatch: Handle jiffies wrap-around

The test used in the linkwatch does not handle wrap-arounds correctly.
Since the intention of the code is to eliminate bursts of messages we
can afford to delay things up to a second.  Using that fact we can
easily handle wrap-arounds by making sure that we don't delay things
by more than one second.

This is based on diagnosis and a patch by Stefan Rompf.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Stefan Rompf <stefan@loplof.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 341de44c7ed1e884f1d036ff74c94d884f6714ea..646937cc2d84db521aeff0b4eedb7a1bc89670d5 100644 (file)
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -170,13 +170,13 @@ void linkwatch_fire_event(struct net_device *dev)
                spin_unlock_irqrestore(&lweventlist_lock, flags);
 
                if (!test_and_set_bit(LW_RUNNING, &linkwatch_flags)) {
-                       unsigned long thisevent = jiffies;
+                       unsigned long delay = linkwatch_nextevent - jiffies;
 
-                       if (thisevent >= linkwatch_nextevent) {
+                       /* If we wrap around we'll delay it by at most HZ. */
+                       if (!delay || delay > HZ)
                                schedule_work(&linkwatch_work);
-                       } else {
-                               schedule_delayed_work(&linkwatch_work, linkwatch_nextevent - thisevent);
-                       }
+                       else
+                               schedule_delayed_work(&linkwatch_work, delay);
                }
        }
 }