[NET] link_watch: Always schedule urgent events

Urgent events may be delayed if we already have a non-urgent event
queued for that device.  This patch changes this by making sure that
an urgent event is always looked at immediately.

I've replaced the LW_RUNNING flag by LW_URGENT since whether work
is scheduled is already kept track by the work queue system.

The only complication is that we have to provide some exclusion for
the setting linkwatch_nextevent which is available in the actual
work function.

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

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 4674ae574128e3c4838d1c5076ac7b074c77b5bd..a5e372b9ec4df3a866ff4a26b44c4fed96021b8b 100644 (file)
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -26,7 +26,7 @@
 
 
 enum lw_bits {
-       LW_RUNNING = 0,
+       LW_URGENT = 0,
 };
 
 static unsigned long linkwatch_flags;
@@ -95,18 +95,41 @@ static void linkwatch_add_event(struct net_device *dev)
 }
 
 
-static void linkwatch_schedule_work(unsigned long delay)
+static void linkwatch_schedule_work(int urgent)
 {
-       if (test_and_set_bit(LW_RUNNING, &linkwatch_flags))
+       unsigned long delay = linkwatch_nextevent - jiffies;
+
+       if (test_bit(LW_URGENT, &linkwatch_flags))
                return;
 
-       /* If we wrap around we'll delay it by at most HZ. */
-       if (delay > HZ) {
-               linkwatch_nextevent = jiffies;
+       /* Minimise down-time: drop delay for up event. */
+       if (urgent) {
+               if (test_and_set_bit(LW_URGENT, &linkwatch_flags))
+                       return;
                delay = 0;
        }
 
-       schedule_delayed_work(&linkwatch_work, delay);
+       /* If we wrap around we'll delay it by at most HZ. */
+       if (delay > HZ)
+               delay = 0;
+
+       /*
+        * This is true if we've scheduled it immeditately or if we don't
+        * need an immediate execution and it's already pending.
+        */
+       if (schedule_delayed_work(&linkwatch_work, delay) == !delay)
+               return;
+
+       /* Don't bother if there is nothing urgent. */
+       if (!test_bit(LW_URGENT, &linkwatch_flags))
+               return;
+
+       /* It's already running which is good enough. */
+       if (!cancel_delayed_work(&linkwatch_work))
+               return;
+
+       /* Otherwise we reschedule it again for immediate exection. */
+       schedule_delayed_work(&linkwatch_work, 0);
 }
 
 
@@ -123,7 +146,11 @@ static void __linkwatch_run_queue(int urgent_only)
         */
        if (!urgent_only)
                linkwatch_nextevent = jiffies + HZ;
-       clear_bit(LW_RUNNING, &linkwatch_flags);
+       /* Limit wrap-around effect on delay. */
+       else if (time_after(linkwatch_nextevent, jiffies + HZ))
+               linkwatch_nextevent = jiffies;
+
+       clear_bit(LW_URGENT, &linkwatch_flags);
 
        spin_lock_irq(&lweventlist_lock);
        next = lweventlist;
@@ -166,7 +193,7 @@ static void __linkwatch_run_queue(int urgent_only)
        }
 
        if (lweventlist)
-               linkwatch_schedule_work(linkwatch_nextevent - jiffies);
+               linkwatch_schedule_work(0);
 }
 
 
@@ -187,21 +214,16 @@ static void linkwatch_event(struct work_struct *dummy)
 
 void linkwatch_fire_event(struct net_device *dev)
 {
-       if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
-               unsigned long delay;
+       int urgent = linkwatch_urgent_event(dev);
 
+       if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
                dev_hold(dev);
 
                linkwatch_add_event(dev);
+       } else if (!urgent)
+               return;
 
-               delay = linkwatch_nextevent - jiffies;
-
-               /* Minimise down-time: drop delay for up event. */
-               if (linkwatch_urgent_event(dev))
-                       delay = 0;
-
-               linkwatch_schedule_work(delay);
-       }
+       linkwatch_schedule_work(urgent);
 }
 
 EXPORT_SYMBOL(linkwatch_fire_event);