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