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authorDavid S. Miller <davem@davemloft.net>2008-08-18 00:58:07 -0400
committerDavid S. Miller <davem@davemloft.net>2008-08-18 00:58:07 -0400
commit4335cd2da1e8986fa8aff21a91144d986cb0a5fc (patch)
tree7c39163199086fedc39adad6c733526658d4bc86 /net/sched
parentdef82a1db1fdc4f861c77009e2ee86870c3743b0 (diff)
pkt_sched: Simplify dev_deactivate() polling loop.
The condition under which the previous qdisc has no more references after we've attached &noop_qdisc is that both RUNNING and SCHED are both seen clear while holding the root lock. So just make specifically that check in the polling loop, instead of this overly complex "check without then check with lock held" sequence. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
-rw-r--r--net/sched/sch_generic.c31
1 files changed, 5 insertions, 26 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index ff1c4557e5f8..30b76aec723b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -653,7 +653,7 @@ static void dev_deactivate_queue(struct net_device *dev,
653 } 653 }
654} 654}
655 655
656static bool some_qdisc_is_busy(struct net_device *dev, int lock) 656static bool some_qdisc_is_busy(struct net_device *dev)
657{ 657{
658 unsigned int i; 658 unsigned int i;
659 659
@@ -667,14 +667,12 @@ static bool some_qdisc_is_busy(struct net_device *dev, int lock)
667 q = dev_queue->qdisc_sleeping; 667 q = dev_queue->qdisc_sleeping;
668 root_lock = qdisc_lock(q); 668 root_lock = qdisc_lock(q);
669 669
670 if (lock) 670 spin_lock_bh(root_lock);
671 spin_lock_bh(root_lock);
672 671
673 val = (test_bit(__QDISC_STATE_RUNNING, &q->state) || 672 val = (test_bit(__QDISC_STATE_RUNNING, &q->state) ||
674 test_bit(__QDISC_STATE_SCHED, &q->state)); 673 test_bit(__QDISC_STATE_SCHED, &q->state));
675 674
676 if (lock) 675 spin_unlock_bh(root_lock);
677 spin_unlock_bh(root_lock);
678 676
679 if (val) 677 if (val)
680 return true; 678 return true;
@@ -684,8 +682,6 @@ static bool some_qdisc_is_busy(struct net_device *dev, int lock)
684 682
685void dev_deactivate(struct net_device *dev) 683void dev_deactivate(struct net_device *dev)
686{ 684{
687 bool running;
688
689 netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc); 685 netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
690 dev_deactivate_queue(dev, &dev->rx_queue, &noop_qdisc); 686 dev_deactivate_queue(dev, &dev->rx_queue, &noop_qdisc);
691 687
@@ -695,25 +691,8 @@ void dev_deactivate(struct net_device *dev)
695 synchronize_rcu(); 691 synchronize_rcu();
696 692
697 /* Wait for outstanding qdisc_run calls. */ 693 /* Wait for outstanding qdisc_run calls. */
698 do { 694 while (some_qdisc_is_busy(dev))
699 while (some_qdisc_is_busy(dev, 0)) 695 yield();
700 yield();
701
702 /*
703 * Double-check inside queue lock to ensure that all effects
704 * of the queue run are visible when we return.
705 */
706 running = some_qdisc_is_busy(dev, 1);
707
708 /*
709 * The running flag should never be set at this point because
710 * we've already set dev->qdisc to noop_qdisc *inside* the same
711 * pair of spin locks. That is, if any qdisc_run starts after
712 * our initial test it should see the noop_qdisc and then
713 * clear the RUNNING bit before dropping the queue lock. So
714 * if it is set here then we've found a bug.
715 */
716 } while (WARN_ON_ONCE(running));
717} 696}
718 697
719static void dev_init_scheduler_queue(struct net_device *dev, 698static void dev_init_scheduler_queue(struct net_device *dev,