ARM: 6751/1: vexpress: select applicable errata workarounds in Kconfig

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / sched / sch_generic.c

/*
 * 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 <net/pkt_sched.h>
#include <net/dst.h>

/* 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;

        if (unlikely(skb)) {
                struct net_device *dev = qdisc_dev(q);
                struct netdev_queue *txq;

                /* check the reason of requeuing without tx lock first */
                txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
                if (!netif_tx_queue_frozen_or_stopped(txq)) {
                        q->gso_skb = NULL;
                        q->q.qlen--;
                } else
                        skb = NULL;
        } else {
                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);
                if (net_ratelimit())
                        printk(KERN_WARNING "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_tx_queue_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_ratelimit()))
                        printk(KERN_WARNING "BUG %s code %d qlen %d\n",
                               dev->name, ret, q->q.qlen);

                ret = dev_requeue_skb(skb, q);
        }

        if (ret && netif_tx_queue_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)
{
        unsigned long start_time = jiffies;

        while (qdisc_restart(q)) {
                /*
                 * Postpone processing if
                 * 1. another process needs the CPU;
                 * 2. we've been doing it for too long.
                 */
                if (need_resched() || jiffies != start_time) {
                        __netif_schedule(q);
                        break;
                }
        }

        qdisc_run_end(q);
}

unsigned long dev_trans_start(struct net_device *dev)
{
        unsigned long val, res = dev->trans_start;
        unsigned int i;

        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_tx_queue_stopped(txq) &&
                                    time_after(jiffies, (trans_start +
                                                         dev->watchdog_timeo))) {
                                        some_queue_timedout = 1;
                                        break;
                                }
                        }

                        if (some_queue_timedout) {
                                char drivername[64];
                                WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
                                       dev->name, netdev_drivername(dev, drivername, 64), 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;
                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;
                linkwatch_fire_event(dev);
        }
}
EXPORT_SYMBOL(netif_carrier_off);

/**
 *      netif_notify_peers - notify network peers about existence of @dev
 *      @dev: network device
 *
 * Generate traffic such that interested network peers are aware of
 * @dev, such as by generating a gratuitous ARP. This may be used when
 * a device wants to inform the rest of the network about some sort of
 * reconfiguration such as a failover event or virtual machine
 * migration.
 */
void netif_notify_peers(struct net_device *dev)
{
        rtnl_lock();
        call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
        rtnl_unlock();
}
EXPORT_SYMBOL(netif_notify_peers);

/* "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);
        NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
        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));

        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,
};

struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
                          struct Qdisc_ops *ops)
{
        void *p;
        struct Qdisc *sch;
        unsigned int size;
        int err = -ENOBUFS;

        /* ensure that the Qdisc and the private data are 64-byte aligned */
        size = QDISC_ALIGN(sizeof(*sch));
        size += ops->priv_size + (QDISC_ALIGNTO - 1);

        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);
        sch->padded = (char *) sch - (char *) p;

        INIT_LIST_HEAD(&sch->list);
        skb_queue_head_init(&sch->q);
        spin_lock_init(&sch->busylock);
        sch->ops = ops;
        sch->enqueue = ops->enqueue;
        sch->dequeue = ops->dequeue;
        sch->dev_queue = dev_queue;
        dev_hold(qdisc_dev(sch));
        atomic_set(&sch->refcnt, 1);

        return sch;
errout:
        return ERR_PTR(err);
}

struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
                                struct Qdisc_ops *ops, unsigned int parentid)
{
        struct Qdisc *sch;

        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(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;
}

static void attach_one_default_qdisc(struct net_device *dev,
                                     struct netdev_queue *dev_queue,
                                     void *_unused)
{
        struct Qdisc *qdisc;

        if (dev->tx_queue_len) {
                qdisc = qdisc_create_dflt(dev_queue,
                                          &pfifo_fast_ops, TC_H_ROOT);
                if (!qdisc) {
                        printk(KERN_INFO "%s: activation failed\n", dev->name);
                        return;
                }

                /* Can by-pass the queue discipline for default qdisc */
                qdisc->flags |= TCQ_F_CAN_BYPASS;
        } else {
                qdisc =  &noqueue_qdisc;
        }
        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) {
                        qdisc->ops->attach(qdisc);
                        dev->qdisc = 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 i.e. pfifo_fast 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);
        }
}

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;
}

void dev_deactivate_many(struct list_head *head)
{
        struct net_device *dev;

        list_for_each_entry(dev, head, unreg_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);
        }

        /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
        synchronize_rcu();

        /* Wait for outstanding qdisc_run calls. */
        list_for_each_entry(dev, head, unreg_list)
                while (some_qdisc_is_busy(dev))
                        yield();
}

void dev_deactivate(struct net_device *dev)
{
        LIST_HEAD(single);

        list_add(&dev->unreg_list, &single);
        dev_deactivate_many(&single);
}

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));
}