Commit b9a3b110 authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatarDavid S. Miller <davem@davemloft.net>
parent 26b284de

net/sched/sch_generic.c

+6 −5
Original line number Diff line number Diff line
@@ -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

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