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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 <davem@davemloft.net>
This commit is contained in:
David S. Miller 2008-08-13 15:18:38 -07:00
parent 26b284de54
commit b9a3b1102b
1 changed files with 6 additions and 5 deletions
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11
net/sched/sch_generic.c
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@ -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