From: Jarek Poplawski

Date: Wed, 13 Aug 2008 06:53:03 +0000
> Otherwise, I think you would better send some code example with these

quoted text
> flags, so we could be sure there is no misunderstanding around this.

Here it my concrete proposal for a fix.
pkt_sched: Fix queue quiescence testing in dev_deactivate().
Based upon discussions with Jarek P. and Herbert Xu.
First, we're testing the wrong qdisc.  We just reset the device

queue qdiscs to &noop_qdisc and checking it's state is completely

pointless here.
We want to wait until the previous qdisc that was sitting at

the ->qdisc pointer is not busy any more.  And that would be

->qdisc_sleeping.
Because of how we propagate the samples qdisc pointer down into

qdisc_run and friends via per-cpu ->output_queue and netif_schedule,

we have to wait also for the __QDISC_STATE_SCHED bit to clear as

well.
Signed-off-by: David S. Miller 
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c

index 7cf83b3..4685746 100644

--- a/net/sched/sch_generic.c

+++ b/net/sched/sch_generic.c

@@ -647,7 +647,7 @@ static void dev_deactivate_queue(struct net_device *dev,

 	}

 }
-static bool some_qdisc_is_running(struct net_device *dev, int lock)

+static bool some_qdisc_is_busy(struct net_device *dev, int lock)

 {

 	unsigned int i;
@@ -658,13 +658,14 @@ static bool some_qdisc_is_running(struct net_device *dev, int lock)

 		int val;
 		dev_queue = netdev_get_tx_queue(dev, i);

-		q = dev_queue->qdisc;

+		q = dev_queue->qdisc_sleeping;

 		root_lock = qdisc_lock(q);
 		if (lock)

 			spin_lock_bh(root_lock);
-		val = test_bit(__QDISC_STATE_RUNNING, &q->state);

+		val = (test_bit(__QDISC_STATE_RUNNING, &q->state) ||

+		       test_bit(__QDISC_STATE_SCHED, &q->state));
 		if (lock)

 			spin_unlock_bh(root_lock);

@@ -689,14 +690,14 @@ void dev_deactivate(struct net_device *dev)
 	/* Wait for outstanding qdisc_run calls. */

 	do {

-		while (some_qdisc_is_running(dev, 0))

+		while (some_qdisc_is_busy(dev, 0))

 			yield();
 		/*

 		 * Double-check inside queue lock to ensure that all effects

 		 * of the queue run are visible when we return.

 		 */

-		running = some_qdisc_is_running(dev, 1);

+		running = some_qdisc_is_busy(dev, 1);
 		/*

 		 * The running flag should never be set at this point because

--

To unsubscribe from this list: send the line "unsubscribe netdev" in

the body of a message to majordomo@vger.kernel.org

More majordomo info at  http://vger.kernel.org/majordomo-info.html