sch_generic.c

Go to the documentation of this file.

/*
 * 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, <[email protected]>
 *              Jamal Hadi Salim, <[email protected]> 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_xmit_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);
        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 = 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_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);
}

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);

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);

/* "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,
};
EXPORT_SYMBOL(pfifo_fast_ops);

static struct lock_class_key qdisc_tx_busylock;

struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
              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,
                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(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,
                      &pfifo_fast_ops, TC_H_ROOT);
        if (!qdisc) {
            netdev_info(dev, "activation failed\n");
            return;
        }
    }
    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);
    }
}
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;
}

void dev_deactivate_many(struct list_head *head)
{
    struct net_device *dev;
    bool sync_needed = false;

    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);
        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, 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);
    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));
}