linux/net/sched/sch_generic.c
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   1/*
   2 * net/sched/sch_generic.c      Generic packet scheduler routines.
   3 *
   4 *              This program is free software; you can redistribute it and/or
   5 *              modify it under the terms of the GNU General Public License
   6 *              as published by the Free Software Foundation; either version
   7 *              2 of the License, or (at your option) any later version.
   8 *
   9 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  10 *              Jamal Hadi Salim, <hadi@cyberus.ca> 990601
  11 *              - Ingress support
  12 */
  13
  14#include <linux/bitops.h>
  15#include <linux/module.h>
  16#include <linux/types.h>
  17#include <linux/kernel.h>
  18#include <linux/sched.h>
  19#include <linux/string.h>
  20#include <linux/errno.h>
  21#include <linux/netdevice.h>
  22#include <linux/skbuff.h>
  23#include <linux/rtnetlink.h>
  24#include <linux/init.h>
  25#include <linux/rcupdate.h>
  26#include <linux/list.h>
  27#include <linux/slab.h>
  28#include <net/pkt_sched.h>
  29#include <net/dst.h>
  30
  31/* Main transmission queue. */
  32
  33/* Modifications to data participating in scheduling must be protected with
  34 * qdisc_lock(qdisc) spinlock.
  35 *
  36 * The idea is the following:
  37 * - enqueue, dequeue are serialized via qdisc root lock
  38 * - ingress filtering is also serialized via qdisc root lock
  39 * - updates to tree and tree walking are only done under the rtnl mutex.
  40 */
  41
  42static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
  43{
  44        skb_dst_force(skb);
  45        q->gso_skb = skb;
  46        q->qstats.requeues++;
  47        q->q.qlen++;    /* it's still part of the queue */
  48        __netif_schedule(q);
  49
  50        return 0;
  51}
  52
  53static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
  54{
  55        struct sk_buff *skb = q->gso_skb;
  56
  57        if (unlikely(skb)) {
  58                struct net_device *dev = qdisc_dev(q);
  59                struct netdev_queue *txq;
  60
  61                /* check the reason of requeuing without tx lock first */
  62                txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
  63                if (!netif_tx_queue_stopped(txq) &&
  64                    !netif_tx_queue_frozen(txq)) {
  65                        q->gso_skb = NULL;
  66                        q->q.qlen--;
  67                } else
  68                        skb = NULL;
  69        } else {
  70                skb = q->dequeue(q);
  71        }
  72
  73        return skb;
  74}
  75
  76static inline int handle_dev_cpu_collision(struct sk_buff *skb,
  77                                           struct netdev_queue *dev_queue,
  78                                           struct Qdisc *q)
  79{
  80        int ret;
  81
  82        if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
  83                /*
  84                 * Same CPU holding the lock. It may be a transient
  85                 * configuration error, when hard_start_xmit() recurses. We
  86                 * detect it by checking xmit owner and drop the packet when
  87                 * deadloop is detected. Return OK to try the next skb.
  88                 */
  89                kfree_skb(skb);
  90                if (net_ratelimit())
  91                        printk(KERN_WARNING "Dead loop on netdevice %s, "
  92                               "fix it urgently!\n", dev_queue->dev->name);
  93                ret = qdisc_qlen(q);
  94        } else {
  95                /*
  96                 * Another cpu is holding lock, requeue & delay xmits for
  97                 * some time.
  98                 */
  99                __this_cpu_inc(softnet_data.cpu_collision);
 100                ret = dev_requeue_skb(skb, q);
 101        }
 102
 103        return ret;
 104}
 105
 106/*
 107 * Transmit one skb, and handle the return status as required. Holding the
 108 * __QDISC_STATE_RUNNING bit guarantees that only one CPU can execute this
 109 * function.
 110 *
 111 * Returns to the caller:
 112 *                              0  - queue is empty or throttled.
 113 *                              >0 - queue is not empty.
 114 */
 115int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
 116                    struct net_device *dev, struct netdev_queue *txq,
 117                    spinlock_t *root_lock)
 118{
 119        int ret = NETDEV_TX_BUSY;
 120
 121        /* And release qdisc */
 122        spin_unlock(root_lock);
 123
 124        HARD_TX_LOCK(dev, txq, smp_processor_id());
 125        if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
 126                ret = dev_hard_start_xmit(skb, dev, txq);
 127
 128        HARD_TX_UNLOCK(dev, txq);
 129
 130        spin_lock(root_lock);
 131
 132        if (dev_xmit_complete(ret)) {
 133                /* Driver sent out skb successfully or skb was consumed */
 134                ret = qdisc_qlen(q);
 135        } else if (ret == NETDEV_TX_LOCKED) {
 136                /* Driver try lock failed */
 137                ret = handle_dev_cpu_collision(skb, txq, q);
 138        } else {
 139                /* Driver returned NETDEV_TX_BUSY - requeue skb */
 140                if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
 141                        printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 142                               dev->name, ret, q->q.qlen);
 143
 144                ret = dev_requeue_skb(skb, q);
 145        }
 146
 147        if (ret && (netif_tx_queue_stopped(txq) ||
 148                    netif_tx_queue_frozen(txq)))
 149                ret = 0;
 150
 151        return ret;
 152}
 153
 154/*
 155 * NOTE: Called under qdisc_lock(q) with locally disabled BH.
 156 *
 157 * __QDISC_STATE_RUNNING guarantees only one CPU can process
 158 * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
 159 * this queue.
 160 *
 161 *  netif_tx_lock serializes accesses to device driver.
 162 *
 163 *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
 164 *  if one is grabbed, another must be free.
 165 *
 166 * Note, that this procedure can be called by a watchdog timer
 167 *
 168 * Returns to the caller:
 169 *                              0  - queue is empty or throttled.
 170 *                              >0 - queue is not empty.
 171 *
 172 */
 173static inline int qdisc_restart(struct Qdisc *q)
 174{
 175        struct netdev_queue *txq;
 176        struct net_device *dev;
 177        spinlock_t *root_lock;
 178        struct sk_buff *skb;
 179
 180        /* Dequeue packet */
 181        skb = dequeue_skb(q);
 182        if (unlikely(!skb))
 183                return 0;
 184        WARN_ON_ONCE(skb_dst_is_noref(skb));
 185        root_lock = qdisc_lock(q);
 186        dev = qdisc_dev(q);
 187        txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
 188
 189        return sch_direct_xmit(skb, q, dev, txq, root_lock);
 190}
 191
 192void __qdisc_run(struct Qdisc *q)
 193{
 194        unsigned long start_time = jiffies;
 195
 196        while (qdisc_restart(q)) {
 197                /*
 198                 * Postpone processing if
 199                 * 1. another process needs the CPU;
 200                 * 2. we've been doing it for too long.
 201                 */
 202                if (need_resched() || jiffies != start_time) {
 203                        __netif_schedule(q);
 204                        break;
 205                }
 206        }
 207
 208        qdisc_run_end(q);
 209}
 210
 211unsigned long dev_trans_start(struct net_device *dev)
 212{
 213        unsigned long val, res = dev->trans_start;
 214        unsigned int i;
 215
 216        for (i = 0; i < dev->num_tx_queues; i++) {
 217                val = netdev_get_tx_queue(dev, i)->trans_start;
 218                if (val && time_after(val, res))
 219                        res = val;
 220        }
 221        dev->trans_start = res;
 222        return res;
 223}
 224EXPORT_SYMBOL(dev_trans_start);
 225
 226static void dev_watchdog(unsigned long arg)
 227{
 228        struct net_device *dev = (struct net_device *)arg;
 229
 230        netif_tx_lock(dev);
 231        if (!qdisc_tx_is_noop(dev)) {
 232                if (netif_device_present(dev) &&
 233                    netif_running(dev) &&
 234                    netif_carrier_ok(dev)) {
 235                        int some_queue_timedout = 0;
 236                        unsigned int i;
 237                        unsigned long trans_start;
 238
 239                        for (i = 0; i < dev->num_tx_queues; i++) {
 240                                struct netdev_queue *txq;
 241
 242                                txq = netdev_get_tx_queue(dev, i);
 243                                /*
 244                                 * old device drivers set dev->trans_start
 245                                 */
 246                                trans_start = txq->trans_start ? : dev->trans_start;
 247                                if (netif_tx_queue_stopped(txq) &&
 248                                    time_after(jiffies, (trans_start +
 249                                                         dev->watchdog_timeo))) {
 250                                        some_queue_timedout = 1;
 251                                        break;
 252                                }
 253                        }
 254
 255                        if (some_queue_timedout) {
 256                                char drivername[64];
 257                                WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
 258                                       dev->name, netdev_drivername(dev, drivername, 64), i);
 259                                dev->netdev_ops->ndo_tx_timeout(dev);
 260                        }
 261                        if (!mod_timer(&dev->watchdog_timer,
 262                                       round_jiffies(jiffies +
 263                                                     dev->watchdog_timeo)))
 264                                dev_hold(dev);
 265                }
 266        }
 267        netif_tx_unlock(dev);
 268
 269        dev_put(dev);
 270}
 271
 272void __netdev_watchdog_up(struct net_device *dev)
 273{
 274        if (dev->netdev_ops->ndo_tx_timeout) {
 275                if (dev->watchdog_timeo <= 0)
 276                        dev->watchdog_timeo = 5*HZ;
 277                if (!mod_timer(&dev->watchdog_timer,
 278                               round_jiffies(jiffies + dev->watchdog_timeo)))
 279                        dev_hold(dev);
 280        }
 281}
 282
 283static void dev_watchdog_up(struct net_device *dev)
 284{
 285        __netdev_watchdog_up(dev);
 286}
 287
 288static void dev_watchdog_down(struct net_device *dev)
 289{
 290        netif_tx_lock_bh(dev);
 291        if (del_timer(&dev->watchdog_timer))
 292                dev_put(dev);
 293        netif_tx_unlock_bh(dev);
 294}
 295
 296/**
 297 *      netif_carrier_on - set carrier
 298 *      @dev: network device
 299 *
 300 * Device has detected that carrier.
 301 */
 302void netif_carrier_on(struct net_device *dev)
 303{
 304        if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 305                if (dev->reg_state == NETREG_UNINITIALIZED)
 306                        return;
 307                linkwatch_fire_event(dev);
 308                if (netif_running(dev))
 309                        __netdev_watchdog_up(dev);
 310        }
 311}
 312EXPORT_SYMBOL(netif_carrier_on);
 313
 314/**
 315 *      netif_carrier_off - clear carrier
 316 *      @dev: network device
 317 *
 318 * Device has detected loss of carrier.
 319 */
 320void netif_carrier_off(struct net_device *dev)
 321{
 322        if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 323                if (dev->reg_state == NETREG_UNINITIALIZED)
 324                        return;
 325                linkwatch_fire_event(dev);
 326        }
 327}
 328EXPORT_SYMBOL(netif_carrier_off);
 329
 330/**
 331 *      netif_notify_peers - notify network peers about existence of @dev
 332 *      @dev: network device
 333 *
 334 * Generate traffic such that interested network peers are aware of
 335 * @dev, such as by generating a gratuitous ARP. This may be used when
 336 * a device wants to inform the rest of the network about some sort of
 337 * reconfiguration such as a failover event or virtual machine
 338 * migration.
 339 */
 340void netif_notify_peers(struct net_device *dev)
 341{
 342        rtnl_lock();
 343        call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
 344        rtnl_unlock();
 345}
 346EXPORT_SYMBOL(netif_notify_peers);
 347
 348/* "NOOP" scheduler: the best scheduler, recommended for all interfaces
 349   under all circumstances. It is difficult to invent anything faster or
 350   cheaper.
 351 */
 352
 353static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
 354{
 355        kfree_skb(skb);
 356        return NET_XMIT_CN;
 357}
 358
 359static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
 360{
 361        return NULL;
 362}
 363
 364struct Qdisc_ops noop_qdisc_ops __read_mostly = {
 365        .id             =       "noop",
 366        .priv_size      =       0,
 367        .enqueue        =       noop_enqueue,
 368        .dequeue        =       noop_dequeue,
 369        .peek           =       noop_dequeue,
 370        .owner          =       THIS_MODULE,
 371};
 372
 373static struct netdev_queue noop_netdev_queue = {
 374        .qdisc          =       &noop_qdisc,
 375        .qdisc_sleeping =       &noop_qdisc,
 376};
 377
 378struct Qdisc noop_qdisc = {
 379        .enqueue        =       noop_enqueue,
 380        .dequeue        =       noop_dequeue,
 381        .flags          =       TCQ_F_BUILTIN,
 382        .ops            =       &noop_qdisc_ops,
 383        .list           =       LIST_HEAD_INIT(noop_qdisc.list),
 384        .q.lock         =       __SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
 385        .dev_queue      =       &noop_netdev_queue,
 386        .busylock       =       __SPIN_LOCK_UNLOCKED(noop_qdisc.busylock),
 387};
 388EXPORT_SYMBOL(noop_qdisc);
 389
 390static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
 391        .id             =       "noqueue",
 392        .priv_size      =       0,
 393        .enqueue        =       noop_enqueue,
 394        .dequeue        =       noop_dequeue,
 395        .peek           =       noop_dequeue,
 396        .owner          =       THIS_MODULE,
 397};
 398
 399static struct Qdisc noqueue_qdisc;
 400static struct netdev_queue noqueue_netdev_queue = {
 401        .qdisc          =       &noqueue_qdisc,
 402        .qdisc_sleeping =       &noqueue_qdisc,
 403};
 404
 405static struct Qdisc noqueue_qdisc = {
 406        .enqueue        =       NULL,
 407        .dequeue        =       noop_dequeue,
 408        .flags          =       TCQ_F_BUILTIN,
 409        .ops            =       &noqueue_qdisc_ops,
 410        .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
 411        .q.lock         =       __SPIN_LOCK_UNLOCKED(noqueue_qdisc.q.lock),
 412        .dev_queue      =       &noqueue_netdev_queue,
 413        .busylock       =       __SPIN_LOCK_UNLOCKED(noqueue_qdisc.busylock),
 414};
 415
 416
 417static const u8 prio2band[TC_PRIO_MAX+1] =
 418        { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
 419
 420/* 3-band FIFO queue: old style, but should be a bit faster than
 421   generic prio+fifo combination.
 422 */
 423
 424#define PFIFO_FAST_BANDS 3
 425
 426/*
 427 * Private data for a pfifo_fast scheduler containing:
 428 *      - queues for the three band
 429 *      - bitmap indicating which of the bands contain skbs
 430 */
 431struct pfifo_fast_priv {
 432        u32 bitmap;
 433        struct sk_buff_head q[PFIFO_FAST_BANDS];
 434};
 435
 436/*
 437 * Convert a bitmap to the first band number where an skb is queued, where:
 438 *      bitmap=0 means there are no skbs on any band.
 439 *      bitmap=1 means there is an skb on band 0.
 440 *      bitmap=7 means there are skbs on all 3 bands, etc.
 441 */
 442static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0};
 443
 444static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv,
 445                                             int band)
 446{
 447        return priv->q + band;
 448}
 449
 450static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 451{
 452        if (skb_queue_len(&qdisc->q) < qdisc_dev(qdisc)->tx_queue_len) {
 453                int band = prio2band[skb->priority & TC_PRIO_MAX];
 454                struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
 455                struct sk_buff_head *list = band2list(priv, band);
 456
 457                priv->bitmap |= (1 << band);
 458                qdisc->q.qlen++;
 459                return __qdisc_enqueue_tail(skb, qdisc, list);
 460        }
 461
 462        return qdisc_drop(skb, qdisc);
 463}
 464
 465static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
 466{
 467        struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
 468        int band = bitmap2band[priv->bitmap];
 469
 470        if (likely(band >= 0)) {
 471                struct sk_buff_head *list = band2list(priv, band);
 472                struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list);
 473
 474                qdisc->q.qlen--;
 475                if (skb_queue_empty(list))
 476                        priv->bitmap &= ~(1 << band);
 477
 478                return skb;
 479        }
 480
 481        return NULL;
 482}
 483
 484static struct sk_buff *pfifo_fast_peek(struct Qdisc* qdisc)
 485{
 486        struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
 487        int band = bitmap2band[priv->bitmap];
 488
 489        if (band >= 0) {
 490                struct sk_buff_head *list = band2list(priv, band);
 491
 492                return skb_peek(list);
 493        }
 494
 495        return NULL;
 496}
 497
 498static void pfifo_fast_reset(struct Qdisc* qdisc)
 499{
 500        int prio;
 501        struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
 502
 503        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 504                __qdisc_reset_queue(qdisc, band2list(priv, prio));
 505
 506        priv->bitmap = 0;
 507        qdisc->qstats.backlog = 0;
 508        qdisc->q.qlen = 0;
 509}
 510
 511static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
 512{
 513        struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
 514
 515        memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
 516        NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 517        return skb->len;
 518
 519nla_put_failure:
 520        return -1;
 521}
 522
 523static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
 524{
 525        int prio;
 526        struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
 527
 528        for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 529                skb_queue_head_init(band2list(priv, prio));
 530
 531        return 0;
 532}
 533
 534struct Qdisc_ops pfifo_fast_ops __read_mostly = {
 535        .id             =       "pfifo_fast",
 536        .priv_size      =       sizeof(struct pfifo_fast_priv),
 537        .enqueue        =       pfifo_fast_enqueue,
 538        .dequeue        =       pfifo_fast_dequeue,
 539        .peek           =       pfifo_fast_peek,
 540        .init           =       pfifo_fast_init,
 541        .reset          =       pfifo_fast_reset,
 542        .dump           =       pfifo_fast_dump,
 543        .owner          =       THIS_MODULE,
 544};
 545
 546struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 547                          struct Qdisc_ops *ops)
 548{
 549        void *p;
 550        struct Qdisc *sch;
 551        unsigned int size;
 552        int err = -ENOBUFS;
 553
 554        /* ensure that the Qdisc and the private data are 64-byte aligned */
 555        size = QDISC_ALIGN(sizeof(*sch));
 556        size += ops->priv_size + (QDISC_ALIGNTO - 1);
 557
 558        p = kzalloc(size, GFP_KERNEL);
 559        if (!p)
 560                goto errout;
 561        sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
 562        sch->padded = (char *) sch - (char *) p;
 563
 564        INIT_LIST_HEAD(&sch->list);
 565        skb_queue_head_init(&sch->q);
 566        spin_lock_init(&sch->busylock);
 567        sch->ops = ops;
 568        sch->enqueue = ops->enqueue;
 569        sch->dequeue = ops->dequeue;
 570        sch->dev_queue = dev_queue;
 571        dev_hold(qdisc_dev(sch));
 572        atomic_set(&sch->refcnt, 1);
 573
 574        return sch;
 575errout:
 576        return ERR_PTR(err);
 577}
 578
 579struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
 580                                struct Qdisc_ops *ops, unsigned int parentid)
 581{
 582        struct Qdisc *sch;
 583
 584        sch = qdisc_alloc(dev_queue, ops);
 585        if (IS_ERR(sch))
 586                goto errout;
 587        sch->parent = parentid;
 588
 589        if (!ops->init || ops->init(sch, NULL) == 0)
 590                return sch;
 591
 592        qdisc_destroy(sch);
 593errout:
 594        return NULL;
 595}
 596EXPORT_SYMBOL(qdisc_create_dflt);
 597
 598/* Under qdisc_lock(qdisc) and BH! */
 599
 600void qdisc_reset(struct Qdisc *qdisc)
 601{
 602        const struct Qdisc_ops *ops = qdisc->ops;
 603
 604        if (ops->reset)
 605                ops->reset(qdisc);
 606
 607        if (qdisc->gso_skb) {
 608                kfree_skb(qdisc->gso_skb);
 609                qdisc->gso_skb = NULL;
 610                qdisc->q.qlen = 0;
 611        }
 612}
 613EXPORT_SYMBOL(qdisc_reset);
 614
 615static void qdisc_rcu_free(struct rcu_head *head)
 616{
 617        struct Qdisc *qdisc = container_of(head, struct Qdisc, rcu_head);
 618
 619        kfree((char *) qdisc - qdisc->padded);
 620}
 621
 622void qdisc_destroy(struct Qdisc *qdisc)
 623{
 624        const struct Qdisc_ops  *ops = qdisc->ops;
 625
 626        if (qdisc->flags & TCQ_F_BUILTIN ||
 627            !atomic_dec_and_test(&qdisc->refcnt))
 628                return;
 629
 630#ifdef CONFIG_NET_SCHED
 631        qdisc_list_del(qdisc);
 632
 633        qdisc_put_stab(qdisc->stab);
 634#endif
 635        gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
 636        if (ops->reset)
 637                ops->reset(qdisc);
 638        if (ops->destroy)
 639                ops->destroy(qdisc);
 640
 641        module_put(ops->owner);
 642        dev_put(qdisc_dev(qdisc));
 643
 644        kfree_skb(qdisc->gso_skb);
 645        /*
 646         * gen_estimator est_timer() might access qdisc->q.lock,
 647         * wait a RCU grace period before freeing qdisc.
 648         */
 649        call_rcu(&qdisc->rcu_head, qdisc_rcu_free);
 650}
 651EXPORT_SYMBOL(qdisc_destroy);
 652
 653/* Attach toplevel qdisc to device queue. */
 654struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
 655                              struct Qdisc *qdisc)
 656{
 657        struct Qdisc *oqdisc = dev_queue->qdisc_sleeping;
 658        spinlock_t *root_lock;
 659
 660        root_lock = qdisc_lock(oqdisc);
 661        spin_lock_bh(root_lock);
 662
 663        /* Prune old scheduler */
 664        if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
 665                qdisc_reset(oqdisc);
 666
 667        /* ... and graft new one */
 668        if (qdisc == NULL)
 669                qdisc = &noop_qdisc;
 670        dev_queue->qdisc_sleeping = qdisc;
 671        rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc);
 672
 673        spin_unlock_bh(root_lock);
 674
 675        return oqdisc;
 676}
 677
 678static void attach_one_default_qdisc(struct net_device *dev,
 679                                     struct netdev_queue *dev_queue,
 680                                     void *_unused)
 681{
 682        struct Qdisc *qdisc;
 683
 684        if (dev->tx_queue_len) {
 685                qdisc = qdisc_create_dflt(dev_queue,
 686                                          &pfifo_fast_ops, TC_H_ROOT);
 687                if (!qdisc) {
 688                        printk(KERN_INFO "%s: activation failed\n", dev->name);
 689                        return;
 690                }
 691
 692                /* Can by-pass the queue discipline for default qdisc */
 693                qdisc->flags |= TCQ_F_CAN_BYPASS;
 694        } else {
 695                qdisc =  &noqueue_qdisc;
 696        }
 697        dev_queue->qdisc_sleeping = qdisc;
 698}
 699
 700static void attach_default_qdiscs(struct net_device *dev)
 701{
 702        struct netdev_queue *txq;
 703        struct Qdisc *qdisc;
 704
 705        txq = netdev_get_tx_queue(dev, 0);
 706
 707        if (!netif_is_multiqueue(dev) || dev->tx_queue_len == 0) {
 708                netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
 709                dev->qdisc = txq->qdisc_sleeping;
 710                atomic_inc(&dev->qdisc->refcnt);
 711        } else {
 712                qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT);
 713                if (qdisc) {
 714                        qdisc->ops->attach(qdisc);
 715                        dev->qdisc = qdisc;
 716                }
 717        }
 718}
 719
 720static void transition_one_qdisc(struct net_device *dev,
 721                                 struct netdev_queue *dev_queue,
 722                                 void *_need_watchdog)
 723{
 724        struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
 725        int *need_watchdog_p = _need_watchdog;
 726
 727        if (!(new_qdisc->flags & TCQ_F_BUILTIN))
 728                clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
 729
 730        rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
 731        if (need_watchdog_p && new_qdisc != &noqueue_qdisc) {
 732                dev_queue->trans_start = 0;
 733                *need_watchdog_p = 1;
 734        }
 735}
 736
 737void dev_activate(struct net_device *dev)
 738{
 739        int need_watchdog;
 740
 741        /* No queueing discipline is attached to device;
 742           create default one i.e. pfifo_fast for devices,
 743           which need queueing and noqueue_qdisc for
 744           virtual interfaces
 745         */
 746
 747        if (dev->qdisc == &noop_qdisc)
 748                attach_default_qdiscs(dev);
 749
 750        if (!netif_carrier_ok(dev))
 751                /* Delay activation until next carrier-on event */
 752                return;
 753
 754        need_watchdog = 0;
 755        netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
 756        if (dev_ingress_queue(dev))
 757                transition_one_qdisc(dev, dev_ingress_queue(dev), NULL);
 758
 759        if (need_watchdog) {
 760                dev->trans_start = jiffies;
 761                dev_watchdog_up(dev);
 762        }
 763}
 764
 765static void dev_deactivate_queue(struct net_device *dev,
 766                                 struct netdev_queue *dev_queue,
 767                                 void *_qdisc_default)
 768{
 769        struct Qdisc *qdisc_default = _qdisc_default;
 770        struct Qdisc *qdisc;
 771
 772        qdisc = dev_queue->qdisc;
 773        if (qdisc) {
 774                spin_lock_bh(qdisc_lock(qdisc));
 775
 776                if (!(qdisc->flags & TCQ_F_BUILTIN))
 777                        set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
 778
 779                rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
 780                qdisc_reset(qdisc);
 781
 782                spin_unlock_bh(qdisc_lock(qdisc));
 783        }
 784}
 785
 786static bool some_qdisc_is_busy(struct net_device *dev)
 787{
 788        unsigned int i;
 789
 790        for (i = 0; i < dev->num_tx_queues; i++) {
 791                struct netdev_queue *dev_queue;
 792                spinlock_t *root_lock;
 793                struct Qdisc *q;
 794                int val;
 795
 796                dev_queue = netdev_get_tx_queue(dev, i);
 797                q = dev_queue->qdisc_sleeping;
 798                root_lock = qdisc_lock(q);
 799
 800                spin_lock_bh(root_lock);
 801
 802                val = (qdisc_is_running(q) ||
 803                       test_bit(__QDISC_STATE_SCHED, &q->state));
 804
 805                spin_unlock_bh(root_lock);
 806
 807                if (val)
 808                        return true;
 809        }
 810        return false;
 811}
 812
 813void dev_deactivate(struct net_device *dev)
 814{
 815        netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
 816        if (dev_ingress_queue(dev))
 817                dev_deactivate_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
 818
 819        dev_watchdog_down(dev);
 820
 821        /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
 822        synchronize_rcu();
 823
 824        /* Wait for outstanding qdisc_run calls. */
 825        while (some_qdisc_is_busy(dev))
 826                yield();
 827}
 828
 829static void dev_init_scheduler_queue(struct net_device *dev,
 830                                     struct netdev_queue *dev_queue,
 831                                     void *_qdisc)
 832{
 833        struct Qdisc *qdisc = _qdisc;
 834
 835        dev_queue->qdisc = qdisc;
 836        dev_queue->qdisc_sleeping = qdisc;
 837}
 838
 839void dev_init_scheduler(struct net_device *dev)
 840{
 841        dev->qdisc = &noop_qdisc;
 842        netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
 843        if (dev_ingress_queue(dev))
 844                dev_init_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
 845
 846        setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
 847}
 848
 849static void shutdown_scheduler_queue(struct net_device *dev,
 850                                     struct netdev_queue *dev_queue,
 851                                     void *_qdisc_default)
 852{
 853        struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
 854        struct Qdisc *qdisc_default = _qdisc_default;
 855
 856        if (qdisc) {
 857                rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
 858                dev_queue->qdisc_sleeping = qdisc_default;
 859
 860                qdisc_destroy(qdisc);
 861        }
 862}
 863
 864void dev_shutdown(struct net_device *dev)
 865{
 866        netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
 867        if (dev_ingress_queue(dev))
 868                shutdown_scheduler_queue(dev, dev_ingress_queue(dev), &noop_qdisc);
 869        qdisc_destroy(dev->qdisc);
 870        dev->qdisc = &noop_qdisc;
 871
 872        WARN_ON(timer_pending(&dev->watchdog_timer));
 873}
 874