net/sched/sch_generic.c

   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 <net/pkt_sched.h>
  28
  29 /* Main transmission queue. */
  30
  31 /* Modifications to data participating in scheduling must be protected with
  32  * queue->lock spinlock.
  33  *
  34  * The idea is the following:
  35  * - enqueue, dequeue are serialized via top level device
  36  *   spinlock queue->lock.
  37  * - ingress filtering is serialized via top level device
  38  *   spinlock dev->rx_queue.lock.
  39  * - updates to tree and tree walking are only done under the rtnl mutex.
  40  */
  41
  42 void qdisc_lock_tree(struct net_device *dev)
  43         __acquires(dev->tx_queue.lock)
  44         __acquires(dev->rx_queue.lock)
  45 {
  46         spin_lock_bh(&dev->tx_queue.lock);
  47         spin_lock(&dev->rx_queue.lock);
  48 }
  49 EXPORT_SYMBOL(qdisc_lock_tree);
  50
  51 void qdisc_unlock_tree(struct net_device *dev)
  52         __releases(dev->rx_queue.lock)
  53         __releases(dev->tx_queue.lock)
  54 {
  55         spin_unlock(&dev->rx_queue.lock);
  56         spin_unlock_bh(&dev->tx_queue.lock);
  57 }
  58 EXPORT_SYMBOL(qdisc_unlock_tree);
  59
  60 static inline int qdisc_qlen(struct Qdisc *q)
  61 {
  62         return q->q.qlen;
  63 }
  64
  65 static inline int dev_requeue_skb(struct sk_buff *skb,
  66                                   struct netdev_queue *dev_queue,
  67                                   struct Qdisc *q)
  68 {
  69         if (unlikely(skb->next))
  70                 dev_queue->gso_skb = skb;
  71         else
  72                 q->ops->requeue(skb, q);
  73
  74         netif_schedule_queue(dev_queue);
  75         return 0;
  76 }
  77
  78 static inline struct sk_buff *dequeue_skb(struct netdev_queue *dev_queue,
  79                                           struct Qdisc *q)
  80 {
  81         struct sk_buff *skb;
  82
  83         if ((skb = dev_queue->gso_skb))
  84                 dev_queue->gso_skb = NULL;
  85         else
  86                 skb = q->dequeue(q);
  87
  88         return skb;
  89 }
  90
  91 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
  92                                            struct netdev_queue *dev_queue,
  93                                            struct Qdisc *q)
  94 {
  95         struct net_device *dev = dev_queue->dev;
  96         int ret;
  97
  98         if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
  99                 /*
 100                  * Same CPU holding the lock. It may be a transient
 101                  * configuration error, when hard_start_xmit() recurses. We
 102                  * detect it by checking xmit owner and drop the packet when
 103                  * deadloop is detected. Return OK to try the next skb.
 104                  */
 105                 kfree_skb(skb);
 106                 if (net_ratelimit())
 107                         printk(KERN_WARNING "Dead loop on netdevice %s, "
 108                                "fix it urgently!\n", dev->name);
 109                 ret = qdisc_qlen(q);
 110         } else {
 111                 /*
 112                  * Another cpu is holding lock, requeue & delay xmits for
 113                  * some time.
 114                  */
 115                 __get_cpu_var(netdev_rx_stat).cpu_collision++;
 116                 ret = dev_requeue_skb(skb, dev_queue, q);
 117         }
 118
 119         return ret;
 120 }
 121
 122 /*
 123  * NOTE: Called under queue->lock with locally disabled BH.
 124  *
 125  * __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
 126  * device at a time. queue->lock serializes queue accesses for
 127  * this device AND txq->qdisc pointer itself.
 128  *
 129  *  netif_tx_lock serializes accesses to device driver.
 130  *
 131  *  queue->lock and netif_tx_lock are mutually exclusive,
 132  *  if one is grabbed, another must be free.
 133  *
 134  * Note, that this procedure can be called by a watchdog timer
 135  *
 136  * Returns to the caller:
 137  *                              0  - queue is empty or throttled.
 138  *                              >0 - queue is not empty.
 139  *
 140  */
 141 static inline int qdisc_restart(struct netdev_queue *txq)
 142 {
 143         struct Qdisc *q = txq->qdisc;
 144         int ret = NETDEV_TX_BUSY;
 145         struct net_device *dev;
 146         struct sk_buff *skb;
 147
 148         /* Dequeue packet */
 149         if (unlikely((skb = dequeue_skb(txq, q)) == NULL))
 150                 return 0;
 151
 152
 153         /* And release queue */
 154         spin_unlock(&txq->lock);
 155
 156         dev = txq->dev;
 157
 158         HARD_TX_LOCK(dev, smp_processor_id());
 159         if (!netif_subqueue_stopped(dev, skb))
 160                 ret = dev_hard_start_xmit(skb, dev);
 161         HARD_TX_UNLOCK(dev);
 162
 163         spin_lock(&txq->lock);
 164         q = txq->qdisc;
 165
 166         switch (ret) {
 167         case NETDEV_TX_OK:
 168                 /* Driver sent out skb successfully */
 169                 ret = qdisc_qlen(q);
 170                 break;
 171
 172         case NETDEV_TX_LOCKED:
 173                 /* Driver try lock failed */
 174                 ret = handle_dev_cpu_collision(skb, txq, q);
 175                 break;
 176
 177         default:
 178                 /* Driver returned NETDEV_TX_BUSY - requeue skb */
 179                 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
 180                         printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 181                                dev->name, ret, q->q.qlen);
 182
 183                 ret = dev_requeue_skb(skb, txq, q);
 184                 break;
 185         }
 186
 187         return ret;
 188 }
 189
 190 void __qdisc_run(struct netdev_queue *txq)
 191 {
 192         struct net_device *dev = txq->dev;
 193         unsigned long start_time = jiffies;
 194
 195         while (qdisc_restart(txq)) {
 196                 if (netif_queue_stopped(dev))
 197                         break;
 198
 199                 /*
 200                  * Postpone processing if
 201                  * 1. another process needs the CPU;
 202                  * 2. we've been doing it for too long.
 203                  */
 204                 if (need_resched() || jiffies != start_time) {
 205                         netif_schedule_queue(txq);
 206                         break;
 207                 }
 208         }
 209
 210         clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
 211 }
 212
 213 static void dev_watchdog(unsigned long arg)
 214 {
 215         struct net_device *dev = (struct net_device *)arg;
 216         struct netdev_queue *txq = &dev->tx_queue;
 217
 218         netif_tx_lock(dev);
 219         if (txq->qdisc != &noop_qdisc) {
 220                 if (netif_device_present(dev) &&
 221                     netif_running(dev) &&
 222                     netif_carrier_ok(dev)) {
 223                         if (netif_queue_stopped(dev) &&
 224                             time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {
 225
 226                                 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
 227                                        dev->name);
 228                                 dev->tx_timeout(dev);
 229                                 WARN_ON_ONCE(1);
 230                         }
 231                         if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo)))
 232                                 dev_hold(dev);
 233                 }
 234         }
 235         netif_tx_unlock(dev);
 236
 237         dev_put(dev);
 238 }
 239
 240 void __netdev_watchdog_up(struct net_device *dev)
 241 {
 242         if (dev->tx_timeout) {
 243                 if (dev->watchdog_timeo <= 0)
 244                         dev->watchdog_timeo = 5*HZ;
 245                 if (!mod_timer(&dev->watchdog_timer,
 246                                round_jiffies(jiffies + dev->watchdog_timeo)))
 247                         dev_hold(dev);
 248         }
 249 }
 250
 251 static void dev_watchdog_up(struct net_device *dev)
 252 {
 253         __netdev_watchdog_up(dev);
 254 }
 255
 256 static void dev_watchdog_down(struct net_device *dev)
 257 {
 258         netif_tx_lock_bh(dev);
 259         if (del_timer(&dev->watchdog_timer))
 260                 dev_put(dev);
 261         netif_tx_unlock_bh(dev);
 262 }
 263
 264 /**
 265  *      netif_carrier_on - set carrier
 266  *      @dev: network device
 267  *
 268  * Device has detected that carrier.
 269  */
 270 void netif_carrier_on(struct net_device *dev)
 271 {
 272         if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 273                 linkwatch_fire_event(dev);
 274                 if (netif_running(dev))
 275                         __netdev_watchdog_up(dev);
 276         }
 277 }
 278 EXPORT_SYMBOL(netif_carrier_on);
 279
 280 /**
 281  *      netif_carrier_off - clear carrier
 282  *      @dev: network device
 283  *
 284  * Device has detected loss of carrier.
 285  */
 286 void netif_carrier_off(struct net_device *dev)
 287 {
 288         if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
 289                 linkwatch_fire_event(dev);
 290 }
 291 EXPORT_SYMBOL(netif_carrier_off);
 292
 293 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
 294    under all circumstances. It is difficult to invent anything faster or
 295    cheaper.
 296  */
 297
 298 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
 299 {
 300         kfree_skb(skb);
 301         return NET_XMIT_CN;
 302 }
 303
 304 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
 305 {
 306         return NULL;
 307 }
 308
 309 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 310 {
 311         if (net_ratelimit())
 312                 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
 313                        skb->dev->name);
 314         kfree_skb(skb);
 315         return NET_XMIT_CN;
 316 }
 317
 318 struct Qdisc_ops noop_qdisc_ops __read_mostly = {
 319         .id             =       "noop",
 320         .priv_size      =       0,
 321         .enqueue        =       noop_enqueue,
 322         .dequeue        =       noop_dequeue,
 323         .requeue        =       noop_requeue,
 324         .owner          =       THIS_MODULE,
 325 };
 326
 327 struct Qdisc noop_qdisc = {
 328         .enqueue        =       noop_enqueue,
 329         .dequeue        =       noop_dequeue,
 330         .flags          =       TCQ_F_BUILTIN,
 331         .ops            =       &noop_qdisc_ops,
 332         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
 333 };
 334 EXPORT_SYMBOL(noop_qdisc);
 335
 336 static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
 337         .id             =       "noqueue",
 338         .priv_size      =       0,
 339         .enqueue        =       noop_enqueue,
 340         .dequeue        =       noop_dequeue,
 341         .requeue        =       noop_requeue,
 342         .owner          =       THIS_MODULE,
 343 };
 344
 345 static struct Qdisc noqueue_qdisc = {
 346         .enqueue        =       NULL,
 347         .dequeue        =       noop_dequeue,
 348         .flags          =       TCQ_F_BUILTIN,
 349         .ops            =       &noqueue_qdisc_ops,
 350         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
 351 };
 352
 353
 354 static const u8 prio2band[TC_PRIO_MAX+1] =
 355         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
 356
 357 /* 3-band FIFO queue: old style, but should be a bit faster than
 358    generic prio+fifo combination.
 359  */
 360
 361 #define PFIFO_FAST_BANDS 3
 362
 363 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
 364                                              struct Qdisc *qdisc)
 365 {
 366         struct sk_buff_head *list = qdisc_priv(qdisc);
 367         return list + prio2band[skb->priority & TC_PRIO_MAX];
 368 }
 369
 370 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 371 {
 372         struct sk_buff_head *list = prio2list(skb, qdisc);
 373
 374         if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len) {
 375                 qdisc->q.qlen++;
 376                 return __qdisc_enqueue_tail(skb, qdisc, list);
 377         }
 378
 379         return qdisc_drop(skb, qdisc);
 380 }
 381
 382 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
 383 {
 384         int prio;
 385         struct sk_buff_head *list = qdisc_priv(qdisc);
 386
 387         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
 388                 if (!skb_queue_empty(list + prio)) {
 389                         qdisc->q.qlen--;
 390                         return __qdisc_dequeue_head(qdisc, list + prio);
 391                 }
 392         }
 393
 394         return NULL;
 395 }
 396
 397 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 398 {
 399         qdisc->q.qlen++;
 400         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
 401 }
 402
 403 static void pfifo_fast_reset(struct Qdisc* qdisc)
 404 {
 405         int prio;
 406         struct sk_buff_head *list = qdisc_priv(qdisc);
 407
 408         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 409                 __qdisc_reset_queue(qdisc, list + prio);
 410
 411         qdisc->qstats.backlog = 0;
 412         qdisc->q.qlen = 0;
 413 }
 414
 415 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
 416 {
 417         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
 418
 419         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
 420         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 421         return skb->len;
 422
 423 nla_put_failure:
 424         return -1;
 425 }
 426
 427 static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
 428 {
 429         int prio;
 430         struct sk_buff_head *list = qdisc_priv(qdisc);
 431
 432         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 433                 skb_queue_head_init(list + prio);
 434
 435         return 0;
 436 }
 437
 438 static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
 439         .id             =       "pfifo_fast",
 440         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
 441         .enqueue        =       pfifo_fast_enqueue,
 442         .dequeue        =       pfifo_fast_dequeue,
 443         .requeue        =       pfifo_fast_requeue,
 444         .init           =       pfifo_fast_init,
 445         .reset          =       pfifo_fast_reset,
 446         .dump           =       pfifo_fast_dump,
 447         .owner          =       THIS_MODULE,
 448 };
 449
 450 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 451                           struct Qdisc_ops *ops)
 452 {
 453         void *p;
 454         struct Qdisc *sch;
 455         unsigned int size;
 456         int err = -ENOBUFS;
 457
 458         /* ensure that the Qdisc and the private data are 32-byte aligned */
 459         size = QDISC_ALIGN(sizeof(*sch));
 460         size += ops->priv_size + (QDISC_ALIGNTO - 1);
 461
 462         p = kzalloc(size, GFP_KERNEL);
 463         if (!p)
 464                 goto errout;
 465         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
 466         sch->padded = (char *) sch - (char *) p;
 467
 468         INIT_LIST_HEAD(&sch->list);
 469         skb_queue_head_init(&sch->q);
 470         sch->ops = ops;
 471         sch->enqueue = ops->enqueue;
 472         sch->dequeue = ops->dequeue;
 473         sch->dev_queue = dev_queue;
 474         dev_hold(qdisc_dev(sch));
 475         atomic_set(&sch->refcnt, 1);
 476
 477         return sch;
 478 errout:
 479         return ERR_PTR(err);
 480 }
 481
 482 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
 483                                  struct netdev_queue *dev_queue,
 484                                  struct Qdisc_ops *ops,
 485                                  unsigned int parentid)
 486 {
 487         struct Qdisc *sch;
 488
 489         sch = qdisc_alloc(dev_queue, ops);
 490         if (IS_ERR(sch))
 491                 goto errout;
 492         sch->parent = parentid;
 493
 494         if (!ops->init || ops->init(sch, NULL) == 0)
 495                 return sch;
 496
 497         qdisc_destroy(sch);
 498 errout:
 499         return NULL;
 500 }
 501 EXPORT_SYMBOL(qdisc_create_dflt);
 502
 503 /* Under queue->lock and BH! */
 504
 505 void qdisc_reset(struct Qdisc *qdisc)
 506 {
 507         const struct Qdisc_ops *ops = qdisc->ops;
 508
 509         if (ops->reset)
 510                 ops->reset(qdisc);
 511 }
 512 EXPORT_SYMBOL(qdisc_reset);
 513
 514 /* this is the rcu callback function to clean up a qdisc when there
 515  * are no further references to it */
 516
 517 static void __qdisc_destroy(struct rcu_head *head)
 518 {
 519         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
 520         kfree((char *) qdisc - qdisc->padded);
 521 }
 522
 523 /* Under queue->lock and BH! */
 524
 525 void qdisc_destroy(struct Qdisc *qdisc)
 526 {
 527         const struct Qdisc_ops  *ops = qdisc->ops;
 528
 529         if (qdisc->flags & TCQ_F_BUILTIN ||
 530             !atomic_dec_and_test(&qdisc->refcnt))
 531                 return;
 532
 533         list_del(&qdisc->list);
 534         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
 535         if (ops->reset)
 536                 ops->reset(qdisc);
 537         if (ops->destroy)
 538                 ops->destroy(qdisc);
 539
 540         module_put(ops->owner);
 541         dev_put(qdisc_dev(qdisc));
 542         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
 543 }
 544 EXPORT_SYMBOL(qdisc_destroy);
 545
 546 void dev_activate(struct net_device *dev)
 547 {
 548         struct netdev_queue *txq = &dev->tx_queue;
 549
 550         /* No queueing discipline is attached to device;
 551            create default one i.e. pfifo_fast for devices,
 552            which need queueing and noqueue_qdisc for
 553            virtual interfaces
 554          */
 555
 556         if (txq->qdisc_sleeping == &noop_qdisc) {
 557                 struct Qdisc *qdisc;
 558                 if (dev->tx_queue_len) {
 559                         qdisc = qdisc_create_dflt(dev, txq,
 560                                                   &pfifo_fast_ops,
 561                                                   TC_H_ROOT);
 562                         if (qdisc == NULL) {
 563                                 printk(KERN_INFO "%s: activation failed\n", dev->name);
 564                                 return;
 565                         }
 566                         list_add_tail(&qdisc->list, &txq->qdisc_list);
 567                 } else {
 568                         qdisc =  &noqueue_qdisc;
 569                 }
 570                 txq->qdisc_sleeping = qdisc;
 571         }
 572
 573         if (!netif_carrier_ok(dev))
 574                 /* Delay activation until next carrier-on event */
 575                 return;
 576
 577         spin_lock_bh(&txq->lock);
 578         rcu_assign_pointer(txq->qdisc, txq->qdisc_sleeping);
 579         if (txq->qdisc != &noqueue_qdisc) {
 580                 dev->trans_start = jiffies;
 581                 dev_watchdog_up(dev);
 582         }
 583         spin_unlock_bh(&txq->lock);
 584 }
 585
 586 static void dev_deactivate_queue(struct netdev_queue *dev_queue,
 587                                  struct Qdisc *qdisc_default)
 588 {
 589         struct Qdisc *qdisc;
 590         struct sk_buff *skb;
 591
 592         spin_lock_bh(&dev_queue->lock);
 593
 594         qdisc = dev_queue->qdisc;
 595         if (qdisc) {
 596                 dev_queue->qdisc = qdisc_default;
 597                 qdisc_reset(qdisc);
 598         }
 599         skb = dev_queue->gso_skb;
 600         dev_queue->gso_skb = NULL;
 601
 602         spin_unlock_bh(&dev_queue->lock);
 603
 604         kfree_skb(skb);
 605 }
 606
 607 void dev_deactivate(struct net_device *dev)
 608 {
 609         int running;
 610
 611         dev_deactivate_queue(&dev->tx_queue, &noop_qdisc);
 612
 613         dev_watchdog_down(dev);
 614
 615         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
 616         synchronize_rcu();
 617
 618         /* Wait for outstanding qdisc_run calls. */
 619         do {
 620                 while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
 621                         yield();
 622
 623                 /*
 624                  * Double-check inside queue lock to ensure that all effects
 625                  * of the queue run are visible when we return.
 626                  */
 627                 spin_lock_bh(&dev->tx_queue.lock);
 628                 running = test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
 629                 spin_unlock_bh(&dev->tx_queue.lock);
 630
 631                 /*
 632                  * The running flag should never be set at this point because
 633                  * we've already set dev->qdisc to noop_qdisc *inside* the same
 634                  * pair of spin locks.  That is, if any qdisc_run starts after
 635                  * our initial test it should see the noop_qdisc and then
 636                  * clear the RUNNING bit before dropping the queue lock.  So
 637                  * if it is set here then we've found a bug.
 638                  */
 639         } while (WARN_ON_ONCE(running));
 640 }
 641
 642 static void dev_init_scheduler_queue(struct net_device *dev,
 643                                      struct netdev_queue *dev_queue,
 644                                      struct Qdisc *qdisc)
 645 {
 646         dev_queue->qdisc = qdisc;
 647         dev_queue->qdisc_sleeping = qdisc;
 648         INIT_LIST_HEAD(&dev_queue->qdisc_list);
 649 }
 650
 651 void dev_init_scheduler(struct net_device *dev)
 652 {
 653         qdisc_lock_tree(dev);
 654         dev_init_scheduler_queue(dev, &dev->tx_queue, &noop_qdisc);
 655         dev_init_scheduler_queue(dev, &dev->rx_queue, NULL);
 656         qdisc_unlock_tree(dev);
 657
 658         setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
 659 }
 660
 661 static void dev_shutdown_scheduler_queue(struct net_device *dev,
 662                                          struct netdev_queue *dev_queue,
 663                                          struct Qdisc *qdisc_default)
 664 {
 665         struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
 666
 667         if (qdisc) {
 668                 dev_queue->qdisc = qdisc_default;
 669                 dev_queue->qdisc_sleeping = qdisc_default;
 670
 671                 qdisc_destroy(qdisc);
 672         }
 673 }
 674
 675 void dev_shutdown(struct net_device *dev)
 676 {
 677         qdisc_lock_tree(dev);
 678         dev_shutdown_scheduler_queue(dev, &dev->tx_queue, &noop_qdisc);
 679         dev_shutdown_scheduler_queue(dev, &dev->rx_queue, NULL);
 680         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
 681         qdisc_unlock_tree(dev);
 682 }