text: /*
   * net/sched/sch_generic.c	Generic packet scheduler routines.
   *
   *		This program is free software; you can redistribute it and/or
   *		modify it under the terms of the GNU General Public License
   *		as published by the Free Software Foundation; either version
   *		2 of the License, or (at your option) any later version.
   *
   * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
   *              Jamal Hadi Salim, <hadi@cyberus.ca> 990601
   *              - Ingress support
   */
  
  #include <linux/bitops.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <linux/rtnetlink.h>
  #include <linux/init.h>
  #include <linux/rcupdate.h>
  #include <linux/list.h>
  #include <linux/slab.h>
  #include <linux/if_vlan.h>
  #include <net/sch_generic.h>
  #include <net/pkt_sched.h>
  #include <net/dst.h>
  
  /* Qdisc to use by default */
  const struct Qdisc_ops *default_qdisc_ops = &pfifo_fast_ops;
  EXPORT_SYMBOL(default_qdisc_ops);
  
  /* Main transmission queue. */
  
  /* Modifications to data participating in scheduling must be protected with
   * qdisc_lock(qdisc) spinlock.
   *
   * The idea is the following:
   * - enqueue, dequeue are serialized via qdisc root lock
   * - ingress filtering is also serialized via qdisc root lock
   * - updates to tree and tree walking are only done under the rtnl mutex.
   */
  
  static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
  {
  	skb_dst_force(skb);
  	q->gso_skb = skb;
  	q->qstats.requeues++;
  	q->q.qlen++;	/* it's still part of the queue */
  	__netif_schedule(q);
  
  	return 0;
  }
  
  static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
  {
  	struct sk_buff *skb = q->gso_skb;
  	const struct netdev_queue *txq = q->dev_queue;
  
  	if (unlikely(skb)) {
  		/* check the reason of requeuing without tx lock first */
  		txq = netdev_get_tx_queue(txq->dev, skb_get_queue_mapping(skb));
  		if (!netif_xmit_frozen_or_stopped(txq)) {
  			q->gso_skb = NULL;
  			q->q.qlen--;
  		} else
  			skb = NULL;
  	} else {
  		if (!(q->flags & TCQ_F_ONETXQUEUE) || !netif_xmit_frozen_or_stopped(txq))
  			skb = q->dequeue(q);
  	}
  
  	return skb;
  }
  
  static inline int handle_dev_cpu_collision(struct sk_buff *skb,
  					   struct netdev_queue *dev_queue,
  					   struct Qdisc *q)
  {
  	int ret;
  
  	if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
  		/*
  		 * Same CPU holding the lock. It may be a transient
  		 * configuration error, when hard_start_xmit() recurses. We
  		 * detect it by checking xmit owner and drop the packet when
  		 * deadloop is detected. Return OK to try the next skb.
  		 */
  		kfree_skb(skb);
  		net_warn_ratelimited("Dead loop on netdevice %s, fix it urgently!\n",
  				     dev_queue->dev->name);
  		ret = qdisc_qlen(q);
  	} else {
  		/*
  		 * Another cpu is holding lock, requeue & delay xmits for
  		 * some time.
  		 */
  		__this_cpu_inc(softnet_data.cpu_collision);
  		ret = dev_requeue_skb(skb, q);
  	}
  
  	return ret;
  }
  
  /*
   * Transmit one skb, and handle the return status as required. Holding the
   * __QDISC_STATE_RUNNING bit guarantees that only one CPU can execute this
   * function.
   *
   * Returns to the caller:
   *				0  - queue is empty or throttled.
   *				>0 - queue is not empty.
   */
  int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
  		    struct net_device *dev, struct netdev_queue *txq,
  		    spinlock_t *root_lock)
  {
  	int ret = NETDEV_TX_BUSY;
  
  	/* And release qdisc */
  	spin_unlock(root_lock);
  
  	HARD_TX_LOCK(dev, txq, smp_processor_id());
  	if (!netif_xmit_frozen_or_stopped(txq))
  		ret = dev_hard_start_xmit(skb, dev, txq);
  
  	HARD_TX_UNLOCK(dev, txq);
  
  	spin_lock(root_lock);
  
  	if (dev_xmit_complete(ret)) {
  		/* Driver sent out skb successfully or skb was consumed */
  		ret = qdisc_qlen(q);
  	} else if (ret == NETDEV_TX_LOCKED) {
  		/* Driver try lock failed */
  		ret = handle_dev_cpu_collision(skb, txq, q);
  	} else {
  		/* Driver returned NETDEV_TX_BUSY - requeue skb */
  		if (unlikely(ret != NETDEV_TX_BUSY))
  			net_warn_ratelimited("BUG %s code %d qlen %d\n",
  					     dev->name, ret, q->q.qlen);
  
  		ret = dev_requeue_skb(skb, q);
  	}
  
  	if (ret && netif_xmit_frozen_or_stopped(txq))
  		ret = 0;
  
  	return ret;
  }
  
  /*
   * NOTE: Called under qdisc_lock(q) with locally disabled BH.
   *
   * __QDISC_STATE_RUNNING guarantees only one CPU can process
   * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
   * this queue.
   *
   *  netif_tx_lock serializes accesses to device driver.
   *
   *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
   *  if one is grabbed, another must be free.
   *
   * Note, that this procedure can be called by a watchdog timer
   *
   * Returns to the caller:
   *				0  - queue is empty or throttled.
   *				>0 - queue is not empty.
   *
   */
  static inline int qdisc_restart(struct Qdisc *q)
  {
  	struct netdev_queue *txq;
  	struct net_device *dev;
  	spinlock_t *root_lock;
  	struct sk_buff *skb;
  
  	/* Dequeue packet */
  	skb = dequeue_skb(q);
  	if (unlikely(!skb))
  		return 0;
  	WARN_ON_ONCE(skb_dst_is_noref(skb));
  	root_lock = qdisc_lock(q);
  	dev = qdisc_dev(q);
  	txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
  
  	return sch_direct_xmit(skb, q, dev, txq, root_lock);
  }
  
  void __qdisc_run(struct Qdisc *q)
  {
  	int quota = weight_p;
  
  	while (qdisc_restart(q)) {
  		/*
  		 * Ordered by possible occurrence: Postpone processing if
  		 * 1. we've exceeded packet quota
  		 * 2. another process needs the CPU;
  		 */
  		if (--quota <= 0 || need_resched()) {
  			__netif_schedule(q);
  			break;
  		}
  	}
  
  	qdisc_run_end(q);
  }
  
  unsigned long dev_trans_start(struct net_device *dev)
  {
  	unsigned long val, res;
  	unsigned int i;
  
  	if (is_vlan_dev(dev))
  		dev = vlan_dev_real_dev(dev);
  	res = dev->trans_start;
  	for (i = 0; i < dev->num_tx_queues; i++) {
  		val = netdev_get_tx_queue(dev, i)->trans_start;
  		if (val && time_after(val, res))
  			res = val;
  	}
  	dev->trans_start = res;
  
  	return res;
  }
  EXPORT_SYMBOL(dev_trans_start);
  
  static void dev_watchdog(unsigned long arg)
  {
  	struct net_device *dev = (struct net_device *)arg;
  
  	netif_tx_lock(dev);
  	if (!qdisc_tx_is_noop(dev)) {
  		if (netif_device_present(dev) &&
  		    netif_running(dev) &&
  		    netif_carrier_ok(dev)) {
  			int some_queue_timedout = 0;
  			unsigned int i;
  			unsigned long trans_start;
  
  			for (i = 0; i < dev->num_tx_queues; i++) {
  				struct netdev_queue *txq;
  
  				txq = netdev_get_tx_queue(dev, i);
  				/*
  				 * old device drivers set dev->trans_start
  				 */
  				trans_start = txq->trans_start ? : dev->trans_start;
  				if (netif_xmit_stopped(txq) &&
  				    time_after(jiffies, (trans_start +
  							 dev->watchdog_timeo))) {
  					some_queue_timedout = 1;
  					txq->trans_timeout++;
  					break;
  				}
  			}
  
  			if (some_queue_timedout) {
  				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
  				       dev->name, netdev_drivername(dev), i);
  				dev->netdev_ops->ndo_tx_timeout(dev);
  			}
  			if (!mod_timer(&dev->watchdog_timer,
  				       round_jiffies(jiffies +
  						     dev->watchdog_timeo)))
  				dev_hold(dev);
  		}
  	}
  	netif_tx_unlock(dev);
  
  	dev_put(dev);
  }
  
  void __netdev_watchdog_up(struct net_device *dev)
  {
  	if (dev->netdev_ops->ndo_tx_timeout) {
  		if (dev->watchdog_timeo <= 0)
  			dev->watchdog_timeo = 5*HZ;
  		if (!mod_timer(&dev->watchdog_timer,
  			       round_jiffies(jiffies + dev->watchdog_timeo)))
  			dev_hold(dev);
  	}
  }
  
  static void dev_watchdog_up(struct net_device *dev)
  {
  	__netdev_watchdog_up(dev);
  }
  
  static void dev_watchdog_down(struct net_device *dev)
  {
  	netif_tx_lock_bh(dev);
  	if (del_timer(&dev->watchdog_timer))
  		dev_put(dev);
  	netif_tx_unlock_bh(dev);
  }
  
  /**
   *	netif_carrier_on - set carrier
   *	@dev: network device
   *
   * Device has detected that carrier.
   */
  void netif_carrier_on(struct net_device *dev)
  {
  	if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
  		if (dev->reg_state == NETREG_UNINITIALIZED)
  			return;
  		atomic_inc(&dev->carrier_changes);
  		linkwatch_fire_event(dev);
  		if (netif_running(dev))
  			__netdev_watchdog_up(dev);
  	}
  }
  EXPORT_SYMBOL(netif_carrier_on);
  
  /**
   *	netif_carrier_off - clear carrier
   *	@dev: network device
   *
   * Device has detected loss of carrier.
   */
  void netif_carrier_off(struct net_device *dev)
  {
  	if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
  		if (dev->reg_state == NETREG_UNINITIALIZED)
  			return;
  		atomic_inc(&dev->carrier_changes);
  		linkwatch_fire_event(dev);
  	}
  }
  EXPORT_SYMBOL(netif_carrier_off);
  
  /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
     under all circumstances. It is difficult to invent anything faster or
     cheaper.
   */
  
  static int noop_enqueue(struct sk_buff *skb, struct Qdisc *qdisc)
  {
  	kfree_skb(skb);
  	return NET_XMIT_CN;
  }
  
  static struct sk_buff *noop_dequeue(struct Qdisc *qdisc)
  {
  	return NULL;
  }
  
  struct Qdisc_ops noop_qdisc_ops __read_mostly = {
  	.id		=	"noop",
  	.priv_size	=	0,
  	.enqueue	=	noop_enqueue,
  	.dequeue	=	noop_dequeue,
  	.peek		=	noop_dequeue,
  	.owner		=	THIS_MODULE,
  };
  
  static struct netdev_queue noop_netdev_queue = {
  	.qdisc		=	&noop_qdisc,
  	.qdisc_sleeping	=	&noop_qdisc,
  };
  
  struct Qdisc noop_qdisc = {
  	.enqueue	=	noop_enqueue,
  	.dequeue	=	noop_dequeue,
  	.flags		=	TCQ_F_BUILTIN,
  	.ops		=	&noop_qdisc_ops,
  	.list		=	LIST_HEAD_INIT(noop_qdisc.list),
  	.q.lock		=	__SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
  	.dev_queue	=	&noop_netdev_queue,
  	.busylock	=	__SPIN_LOCK_UNLOCKED(noop_qdisc.busylock),
  };
  EXPORT_SYMBOL(noop_qdisc);
  
  static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
  	.id		=	"noqueue",
  	.priv_size	=	0,
  	.enqueue	=	noop_enqueue,
  	.dequeue	=	noop_dequeue,
  	.peek		=	noop_dequeue,
  	.owner		=	THIS_MODULE,
  };
  
  static struct Qdisc noqueue_qdisc;
  static struct netdev_queue noqueue_netdev_queue = {
  	.qdisc		=	&noqueue_qdisc,
  	.qdisc_sleeping	=	&noqueue_qdisc,
  };
  
  static struct Qdisc noqueue_qdisc = {
  	.enqueue	=	NULL,
  	.dequeue	=	noop_dequeue,
  	.flags		=	TCQ_F_BUILTIN,
  	.ops		=	&noqueue_qdisc_ops,
  	.list		=	LIST_HEAD_INIT(noqueue_qdisc.list),
  	.q.lock		=	__SPIN_LOCK_UNLOCKED(noqueue_qdisc.q.lock),
  	.dev_queue	=	&noqueue_netdev_queue,
  	.busylock	=	__SPIN_LOCK_UNLOCKED(noqueue_qdisc.busylock),
  };
  
  
  static const u8 prio2band[TC_PRIO_MAX + 1] = {
  	1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1
  };
  
  /* 3-band FIFO queue: old style, but should be a bit faster than
     generic prio+fifo combination.
   */
  
  #define PFIFO_FAST_BANDS 3
  
  /*
   * Private data for a pfifo_fast scheduler containing:
   * 	- queues for the three band
   * 	- bitmap indicating which of the bands contain skbs
   */
  struct pfifo_fast_priv {
  	u32 bitmap;
  	struct sk_buff_head q[PFIFO_FAST_BANDS];
  };
  
  /*
   * Convert a bitmap to the first band number where an skb is queued, where:
   * 	bitmap=0 means there are no skbs on any band.
   * 	bitmap=1 means there is an skb on band 0.
   *	bitmap=7 means there are skbs on all 3 bands, etc.
   */
  static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0};
  
  static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv,
  					     int band)
  {
  	return priv->q + band;
  }
  
  static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc)
  {
  	if (skb_queue_len(&qdisc->q) < qdisc_dev(qdisc)->tx_queue_len) {
  		int band = prio2band[skb->priority & TC_PRIO_MAX];
  		struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  		struct sk_buff_head *list = band2list(priv, band);
  
  		priv->bitmap |= (1 << band);
  		qdisc->q.qlen++;
  		return __qdisc_enqueue_tail(skb, qdisc, list);
  	}
  
  	return qdisc_drop(skb, qdisc);
  }
  
  static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
  {
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  	int band = bitmap2band[priv->bitmap];
  
  	if (likely(band >= 0)) {
  		struct sk_buff_head *list = band2list(priv, band);
  		struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list);
  
  		qdisc->q.qlen--;
  		if (skb_queue_empty(list))
  			priv->bitmap &= ~(1 << band);
  
  		return skb;
  	}
  
  	return NULL;
  }
  
  static struct sk_buff *pfifo_fast_peek(struct Qdisc *qdisc)
  {
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  	int band = bitmap2band[priv->bitmap];
  
  	if (band >= 0) {
  		struct sk_buff_head *list = band2list(priv, band);
  
  		return skb_peek(list);
  	}
  
  	return NULL;
  }
  
  static void pfifo_fast_reset(struct Qdisc *qdisc)
  {
  	int prio;
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  
  	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
  		__qdisc_reset_queue(qdisc, band2list(priv, prio));
  
  	priv->bitmap = 0;
  	qdisc->qstats.backlog = 0;
  	qdisc->q.qlen = 0;
  }
  
  static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
  {
  	struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
  
  	memcpy(&opt.priomap, prio2band, TC_PRIO_MAX + 1);
  	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
  		goto nla_put_failure;
  	return skb->len;
  
  nla_put_failure:
  	return -1;
  }
  
  static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
  {
  	int prio;
  	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
  
  	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
  		skb_queue_head_init(band2list(priv, prio));
  
  	/* Can by-pass the queue discipline */
  	qdisc->flags |= TCQ_F_CAN_BYPASS;
  	return 0;
  }
  
  struct Qdisc_ops pfifo_fast_ops __read_mostly = {
  	.id		=	"pfifo_fast",
  	.priv_size	=	sizeof(struct pfifo_fast_priv),
  	.enqueue	=	pfifo_fast_enqueue,
  	.dequeue	=	pfifo_fast_dequeue,
  	.peek		=	pfifo_fast_peek,
  	.init		=	pfifo_fast_init,
  	.reset		=	pfifo_fast_reset,
  	.dump		=	pfifo_fast_dump,
  	.owner		=	THIS_MODULE,
  };
  
  static struct lock_class_key qdisc_tx_busylock;
  
  struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
  			  const struct Qdisc_ops *ops)
  {
  	void *p;
  	struct Qdisc *sch;
  	unsigned int size = QDISC_ALIGN(sizeof(*sch)) + ops->priv_size;
  	int err = -ENOBUFS;
  	struct net_device *dev = dev_queue->dev;
  
  	p = kzalloc_node(size, GFP_KERNEL,
  			 netdev_queue_numa_node_read(dev_queue));
  
  	if (!p)
  		goto errout;
  	sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
  	/* if we got non aligned memory, ask more and do alignment ourself */
  	if (sch != p) {
  		kfree(p);
  		p = kzalloc_node(size + QDISC_ALIGNTO - 1, GFP_KERNEL,
  				 netdev_queue_numa_node_read(dev_queue));
  		if (!p)
  			goto errout;
  		sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
  		sch->padded = (char *) sch - (char *) p;
  	}
  	INIT_LIST_HEAD(&sch->list);
  	skb_queue_head_init(&sch->q);
  
  	spin_lock_init(&sch->busylock);
  	lockdep_set_class(&sch->busylock,
  			  dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
  
  	sch->ops = ops;
  	sch->enqueue = ops->enqueue;
  	sch->dequeue = ops->dequeue;
  	sch->dev_queue = dev_queue;
  	dev_hold(dev);
  	atomic_set(&sch->refcnt, 1);
  
  	return sch;
  errout:
  	return ERR_PTR(err);
  }
  
  struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
  				const struct Qdisc_ops *ops,
  				unsigned int parentid)
  {
  	struct Qdisc *sch;
  
  	if (!try_module_get(ops->owner))
  		goto errout;
  
  	sch = qdisc_alloc(dev_queue, ops);
  	if (IS_ERR(sch))
  		goto errout;
  	sch->parent = parentid;
  
  	if (!ops->init || ops->init(sch, NULL) == 0)
  		return sch;
  
  	qdisc_destroy(sch);
  errout:
  	return NULL;
  }
  EXPORT_SYMBOL(qdisc_create_dflt);
  
  /* Under qdisc_lock(qdisc) and BH! */
  
  void qdisc_reset(struct Qdisc *qdisc)
  {
  	const struct Qdisc_ops *ops = qdisc->ops;
  
  	if (ops->reset)
  		ops->reset(qdisc);
  
  	if (qdisc->gso_skb) {
  		kfree_skb(qdisc->gso_skb);
  		qdisc->gso_skb = NULL;
  		qdisc->q.qlen = 0;
  	}
  }
  EXPORT_SYMBOL(qdisc_reset);
  
  static void qdisc_rcu_free(struct rcu_head *head)
  {
  	struct Qdisc *qdisc = container_of(head, struct Qdisc, rcu_head);
  
  	kfree((char *) qdisc - qdisc->padded);
  }
  
  void qdisc_destroy(struct Qdisc *qdisc)
  {
  	const struct Qdisc_ops  *ops = qdisc->ops;
  
  	if (qdisc->flags & TCQ_F_BUILTIN ||
  	    !atomic_dec_and_test(&qdisc->refcnt))
  		return;
  
  #ifdef CONFIG_NET_SCHED
  	qdisc_list_del(qdisc);
  
  	qdisc_put_stab(rtnl_dereference(qdisc->stab));
  #endif
  	gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
  	if (ops->reset)
  		ops->reset(qdisc);
  	if (ops->destroy)
  		ops->destroy(qdisc);
  
  	module_put(ops->owner);
  	dev_put(qdisc_dev(qdisc));
  
  	kfree_skb(qdisc->gso_skb);
  	/*
  	 * gen_estimator est_timer() might access qdisc->q.lock,
  	 * wait a RCU grace period before freeing qdisc.
  	 */
  	call_rcu(&qdisc->rcu_head, qdisc_rcu_free);
  }
  EXPORT_SYMBOL(qdisc_destroy);
  
  /* Attach toplevel qdisc to device queue. */
  struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
  			      struct Qdisc *qdisc)
  {
  	struct Qdisc *oqdisc = dev_queue->qdisc_sleeping;
  	spinlock_t *root_lock;
  
  	root_lock = qdisc_lock(oqdisc);
  	spin_lock_bh(root_lock);
  
  	/* Prune old scheduler */
  	if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
  		qdisc_reset(oqdisc);
  
  	/* ... and graft new one */
  	if (qdisc == NULL)
  		qdisc = &noop_qdisc;
  	dev_queue->qdisc_sleeping = qdisc;
  	rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc);
  
  	spin_unlock_bh(root_lock);
  
  	return oqdisc;
  }
  EXPORT_SYMBOL(dev_graft_qdisc);
  
  static void attach_one_default_qdisc(struct net_device *dev,
  				     struct netdev_queue *dev_queue,
  				     void *_unused)
  {
  	struct Qdisc *qdisc = &noqueue_qdisc;
  
  	if (dev->tx_queue_len) {
  		qdisc = qdisc_create_dflt(dev_queue,
  					  default_qdisc_ops, TC_H_ROOT);
  		if (!qdisc) {
  			netdev_info(dev, "activation failed\n");
  			return;
  		}
  		if (!netif_is_multiqueue(dev))
  			qdisc->flags |= TCQ_F_ONETXQUEUE;
  	}
  	dev_queue->qdisc_sleeping = qdisc;
  }
  
  static void attach_default_qdiscs(struct net_device *dev)
  {
  	struct netdev_queue *txq;
  	struct Qdisc *qdisc;
  
  	txq = netdev_get_tx_queue(dev, 0);
  
  	if (!netif_is_multiqueue(dev) || dev->tx_queue_len == 0) {
  		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
  		dev->qdisc = txq->qdisc_sleeping;
  		atomic_inc(&dev->qdisc->refcnt);
  	} else {
  		qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT);
  		if (qdisc) {
  			dev->qdisc = qdisc;
  			qdisc->ops->attach(qdisc);
  		}
  	}
  }
  
  static void transition_one_qdisc(struct net_device *dev,
  				 struct netdev_queue *dev_queue,
  				 void *_need_watchdog)
  {
  	struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
  	int *need_watchdog_p = _need_watchdog;
  
  	if (!(new_qdisc->flags & TCQ_F_BUILTIN))
  		clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
  
  	rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
  	if (need_watchdog_p && new_qdisc != &noqueue_qdisc) {
  		dev_queue->trans_start = 0;
  		*need_watchdog_p = 1;
  	}
  }
  
  void dev_activate(struct net_device *dev)
  {
  	int need_watchdog;
  
  	/* No queueing discipline is attached to device;
  	 * create default one for devices, which need queueing
  	 * and noqueue_qdisc for virtual interfaces
  	 */
  
  	if (dev->qdisc == &noop_qdisc)
  		attach_default_qdiscs(dev);
  
  	if (!netif_carrier_ok(dev))
  		/* Delay activation until next carrier-on event */
  		return;
  
  	need_watchdog = 0;
  	netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
  	if (dev_ingress_queue(dev))
  		transition_one_qdisc(dev, dev_ingress_queue(dev), NULL);
  
  	if (need_watchdog) {
  		dev->trans_start = jiffies;
  		dev_watchdog_up(dev);
  	}
  }
  EXPORT_SYMBOL(dev_activate);
  
  static void dev_deactivate_queue(struct net_device *dev,
  				 struct netdev_queue *dev_queue,
  				 void *_qdisc_default)
  {
  	struct Qdisc *qdisc_default = _qdisc_default;
  	struct Qdisc *qdisc;
  
  	qdisc = dev_queue->qdisc;
  	if (qdisc) {
  		spin_lock_bh(qdisc_lock(qdisc));
  
  		if (!(qdisc->flags & TCQ_F_BUILTIN))
  			set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
  
  		rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
  		qdisc_reset(qdisc);
  
  		spin_unlock_bh(qdisc_lock(qdisc));
  	}
  }
  
  static bool some_qdisc_is_busy(struct net_device *dev)
  {
  	unsigned int i;
  
  	for (i = 0; i < dev->num_tx_queues; i++) {
  		struct netdev_queue *dev_queue;
  		spinlock_t *root_lock;
  		struct Qdisc *q;
  		int val;
  
  		dev_queue = netdev_get_tx_queue(dev, i);
  		q = dev_queue->qdisc_sleeping;
  		root_lock = qdisc_lock(q);
  
  		spin_lock_bh(root_lock);
  
  		val = (qdisc_is_running(q) ||
  		       test_bit(__QDISC_STATE_SCHED, &q->state));
  
  		spin_unlock_bh(root_lock);
  
  		if (val)
  			return true;
  	}
  	return false;
  }
  
  /**
   * 	dev_deactivate_many - deactivate transmissions on several devices
   * 	@head: list of devices to deactivate
   *
   *	This function returns only when all outstanding transmissions
   *	have completed, unless all devices are in dismantle phase.
   */
  void dev_deactivate_many(struct list_head *head)
  {
  	struct net_device *dev;
  	bool sync_needed = false;
  
  	list_for_each_entry(dev, head, close_list) {
  		netdev_for_each_tx_queue(dev, dev_deactivate_queue,
  					 &noop_qdisc);
  		if (dev_ingress_queue(dev))
  			dev_deactivate_queue(dev, dev_ingress_queue(dev),
  					     &noop_qdisc);
  
  		dev_watchdog_down(dev);
  		sync_needed |= !dev->dismantle;
  	}
  
  	/* Wait for outstanding qdisc-less dev_queue_xmit calls.
  	 * This is avoided if all devices are in dismantle phase :
  	 * Caller will call synchronize_net() for us
  	 */
  	if (sync_needed)
  		synchronize_net();
  
  	/* Wait for outstanding qdisc_run calls. */
  	list_for_each_entry(dev, head, close_list)
  		while (some_qdisc_is_busy(dev))
  			yield();
  }
  
  void dev_deactivate(struct net_device *dev)
  {
  	LIST_HEAD(single);
  
  	list_add(&dev->close_list, &single);
  	dev_deactivate_many(&single);
  	list_del(&single);
  }
  EXPORT_SYMBOL(dev_deactivate);
  
  static void dev_init_scheduler_queue(struct net_device *dev,
  				     struct netdev_queue *dev_queue,
  				     void *_qdisc)
  {
  	struct Qdisc *qdisc = _qdisc;
  
  	dev_queue->qdisc = qdisc;
  	dev_queue->qdisc_sleeping = qdisc;
  }
  
  void dev_init_scheduler(struct net_device *dev)
  {
  	dev->qdisc = &noop_qdisc;
  	netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
  	if (dev_ingress_queue(dev))
  		dev_init_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
  
  	setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
  }
  
  static void shutdown_scheduler_queue(struct net_device *dev,
  				     struct netdev_queue *dev_queue,
  				     void *_qdisc_default)
  {
  	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
  	struct Qdisc *qdisc_default = _qdisc_default;
  
  	if (qdisc) {
  		rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
  		dev_queue->qdisc_sleeping = qdisc_default;
  
  		qdisc_destroy(qdisc);
  	}
  }
  
  void dev_shutdown(struct net_device *dev)
  {
  	netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
  	if (dev_ingress_queue(dev))
  		shutdown_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
  	qdisc_destroy(dev->qdisc);
  	dev->qdisc = &noop_qdisc;
  
  	WARN_ON(timer_pending(&dev->watchdog_timer));
  }
  
  void psched_ratecfg_precompute(struct psched_ratecfg *r,
  			       const struct tc_ratespec *conf,
  			       u64 rate64)
  {
  	memset(r, 0, sizeof(*r));
  	r->overhead = conf->overhead;
  	r->undilated_rate_bytes_ps = max_t(u64, conf->rate, rate64);
  	r->rate_bytes_ps = max_t(u64, conf->rate, rate64);
  
          if (current->dilation > 0) {
  		r->rate_bytes_ps = r->undilated_rate_bytes_ps * 1000 / current->dilation;
  		printk_once("[psched_ratecfg_precompute]: %s(%d) rate dilated(%d) from (%llu) to (%llu)\n",
                                  current->comm, current->pid, current->dilation,
                                  r->undilated_rate_bytes_ps, r->rate_bytes_ps);
  	}
  
  	r->linklayer = (conf->linklayer & TC_LINKLAYER_MASK);
  	r->mult = 1;
  	/*
  	 * The deal here is to replace a divide by a reciprocal one
  	 * in fast path (a reciprocal divide is a multiply and a shift)
  	 *
  	 * Normal formula would be :
  	 *  time_in_ns = (NSEC_PER_SEC * len) / rate_bps
  	 *
  	 * We compute mult/shift to use instead :
  	 *  time_in_ns = (len * mult) >> shift;
  	 *
  	 * We try to get the highest possible mult value for accuracy,
  	 * but have to make sure no overflows will ever happen.
  	 */
  	if (r->rate_bytes_ps > 0) {
  		u64 factor = NSEC_PER_SEC;
  
  		for (;;) {
  			r->mult = div64_u64(factor, r->rate_bytes_ps);
  			if (r->mult & (1U << 31) || factor & (1ULL << 63))
  				break;
  			factor <<= 1;
  			r->shift++;
  		}
  	}
  }
  EXPORT_SYMBOL(psched_ratecfg_precompute);
  
  /**
   * Proactively update rate when host process changes TDF
   * Example: see in htb's htb_dequeue_tree
   */
  void psched_ratecfg_dilate(struct psched_ratecfg *r, int dilation)
  {
  	if (r && dilation > 0) {
  		r->rate_bytes_ps = r->undilated_rate_bytes_ps * 1000 / dilation;
  		printk_once("[psched_ratecfg_dilate] %s(%d) change rate to %llu due to change of TDF(%d)\n",
                                  current->comm, current->pid, r->rate_bytes_ps, dilation);
                  /**
                   * FIXME: not sure what this code does,
                   * but better redo it after updating rate_bytes_ps
                   */
  		r->mult = 1;
  		r->shift = 0;
  		if (r->rate_bytes_ps > 0) {
  			u64 factor = NSEC_PER_SEC;
  
  			for (;;) {
  				r->mult = div64_u64(factor, r->rate_bytes_ps);
  				if (r->mult & (1U << 31) || factor & (1ULL << 63))
  					break;
  				factor <<= 1;
  				r->shift++;
  			}
  		}
  	}
  }
  EXPORT_SYMBOL(psched_ratecfg_dilate);
  
  