[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>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 341de44c7ed1..646937cc2d84 100644
--- 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);
                 }
         }
 }