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  * qdisc_root_lock(qdisc) spinlock.
  33  *
  34  * The idea is the following:
  35  * - enqueue, dequeue are serialized via qdisc root lock
  36  * - ingress filtering is also serialized via qdisc root lock
  37  * - updates to tree and tree walking are only done under the rtnl mutex.
  38  */
  39
  40 static inline int qdisc_qlen(struct Qdisc *q)
  41 {
  42         return q->q.qlen;
  43 }
  44
  45 static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
  46 {
  47         if (unlikely(skb->next))
  48                 q->gso_skb = skb;
  49         else
  50                 q->ops->requeue(skb, q);
  51
  52         __netif_schedule(q);
  53         return 0;
  54 }
  55
  56 static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
  57 {
  58         struct sk_buff *skb;
  59
  60         if ((skb = q->gso_skb))
  61                 q->gso_skb = NULL;
  62         else
  63                 skb = q->dequeue(q);
  64
  65         return skb;
  66 }
  67
  68 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
  69                                            struct netdev_queue *dev_queue,
  70                                            struct Qdisc *q)
  71 {
  72         int ret;
  73
  74         if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
  75                 /*
  76                  * Same CPU holding the lock. It may be a transient
  77                  * configuration error, when hard_start_xmit() recurses. We
  78                  * detect it by checking xmit owner and drop the packet when
  79                  * deadloop is detected. Return OK to try the next skb.
  80                  */
  81                 kfree_skb(skb);
  82                 if (net_ratelimit())
  83                         printk(KERN_WARNING "Dead loop on netdevice %s, "
  84                                "fix it urgently!\n", dev_queue->dev->name);
  85                 ret = qdisc_qlen(q);
  86         } else {
  87                 /*
  88                  * Another cpu is holding lock, requeue & delay xmits for
  89                  * some time.
  90                  */
  91                 __get_cpu_var(netdev_rx_stat).cpu_collision++;
  92                 ret = dev_requeue_skb(skb, q);
  93         }
  94
  95         return ret;
  96 }
  97
  98 /*
  99  * NOTE: Called under qdisc_lock(q) with locally disabled BH.
 100  *
 101  * __QDISC_STATE_RUNNING guarantees only one CPU can process
 102  * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
 103  * this queue.
 104  *
 105  *  netif_tx_lock serializes accesses to device driver.
 106  *
 107  *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
 108  *  if one is grabbed, another must be free.
 109  *
 110  * Note, that this procedure can be called by a watchdog timer
 111  *
 112  * Returns to the caller:
 113  *                              0  - queue is empty or throttled.
 114  *                              >0 - queue is not empty.
 115  *
 116  */
 117 static inline int qdisc_restart(struct Qdisc *q)
 118 {
 119         struct netdev_queue *txq;
 120         int ret = NETDEV_TX_BUSY;
 121         struct net_device *dev;
 122         spinlock_t *root_lock;
 123         struct sk_buff *skb;
 124
 125         /* Dequeue packet */
 126         if (unlikely((skb = dequeue_skb(q)) == NULL))
 127                 return 0;
 128
 129         root_lock = qdisc_root_lock(q);
 130
 131         /* And release qdisc */
 132         spin_unlock(root_lock);
 133
 134         dev = qdisc_dev(q);
 135         txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
 136
 137         HARD_TX_LOCK(dev, txq, smp_processor_id());
 138         if (!netif_subqueue_stopped(dev, skb))
 139                 ret = dev_hard_start_xmit(skb, dev, txq);
 140         HARD_TX_UNLOCK(dev, txq);
 141
 142         spin_lock(root_lock);
 143
 144         switch (ret) {
 145         case NETDEV_TX_OK:
 146                 /* Driver sent out skb successfully */
 147                 ret = qdisc_qlen(q);
 148                 break;
 149
 150         case NETDEV_TX_LOCKED:
 151                 /* Driver try lock failed */
 152                 ret = handle_dev_cpu_collision(skb, txq, q);
 153                 break;
 154
 155         default:
 156                 /* Driver returned NETDEV_TX_BUSY - requeue skb */
 157                 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
 158                         printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 159                                dev->name, ret, q->q.qlen);
 160
 161                 ret = dev_requeue_skb(skb, q);
 162                 break;
 163         }
 164
 165         if (ret && netif_tx_queue_stopped(txq))
 166                 ret = 0;
 167
 168         return ret;
 169 }
 170
 171 void __qdisc_run(struct Qdisc *q)
 172 {
 173         unsigned long start_time = jiffies;
 174
 175         while (qdisc_restart(q)) {
 176                 /*
 177                  * Postpone processing if
 178                  * 1. another process needs the CPU;
 179                  * 2. we've been doing it for too long.
 180                  */
 181                 if (need_resched() || jiffies != start_time) {
 182                         __netif_schedule(q);
 183                         break;
 184                 }
 185         }
 186
 187         clear_bit(__QDISC_STATE_RUNNING, &q->state);
 188 }
 189
 190 static void dev_watchdog(unsigned long arg)
 191 {
 192         struct net_device *dev = (struct net_device *)arg;
 193
 194         netif_tx_lock(dev);
 195         if (!qdisc_tx_is_noop(dev)) {
 196                 if (netif_device_present(dev) &&
 197                     netif_running(dev) &&
 198                     netif_carrier_ok(dev)) {
 199                         int some_queue_stopped = 0;
 200                         unsigned int i;
 201
 202                         for (i = 0; i < dev->num_tx_queues; i++) {
 203                                 struct netdev_queue *txq;
 204
 205                                 txq = netdev_get_tx_queue(dev, i);
 206                                 if (netif_tx_queue_stopped(txq)) {
 207                                         some_queue_stopped = 1;
 208                                         break;
 209                                 }
 210                         }
 211
 212                         if (some_queue_stopped &&
 213                             time_after(jiffies, (dev->trans_start +
 214                                                  dev->watchdog_timeo))) {
 215                                 printk(KERN_INFO "NETDEV WATCHDOG: %s: "
 216                                        "transmit timed out\n",
 217                                        dev->name);
 218                                 dev->tx_timeout(dev);
 219                                 WARN_ON_ONCE(1);
 220                         }
 221                         if (!mod_timer(&dev->watchdog_timer,
 222                                        round_jiffies(jiffies +
 223                                                      dev->watchdog_timeo)))
 224                                 dev_hold(dev);
 225                 }
 226         }
 227         netif_tx_unlock(dev);
 228
 229         dev_put(dev);
 230 }
 231
 232 void __netdev_watchdog_up(struct net_device *dev)
 233 {
 234         if (dev->tx_timeout) {
 235                 if (dev->watchdog_timeo <= 0)
 236                         dev->watchdog_timeo = 5*HZ;
 237                 if (!mod_timer(&dev->watchdog_timer,
 238                                round_jiffies(jiffies + dev->watchdog_timeo)))
 239                         dev_hold(dev);
 240         }
 241 }
 242
 243 static void dev_watchdog_up(struct net_device *dev)
 244 {
 245         __netdev_watchdog_up(dev);
 246 }
 247
 248 static void dev_watchdog_down(struct net_device *dev)
 249 {
 250         netif_tx_lock_bh(dev);
 251         if (del_timer(&dev->watchdog_timer))
 252                 dev_put(dev);
 253         netif_tx_unlock_bh(dev);
 254 }
 255
 256 /**
 257  *      netif_carrier_on - set carrier
 258  *      @dev: network device
 259  *
 260  * Device has detected that carrier.
 261  */
 262 void netif_carrier_on(struct net_device *dev)
 263 {
 264         if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 265                 linkwatch_fire_event(dev);
 266                 if (netif_running(dev))
 267                         __netdev_watchdog_up(dev);
 268         }
 269 }
 270 EXPORT_SYMBOL(netif_carrier_on);
 271
 272 /**
 273  *      netif_carrier_off - clear carrier
 274  *      @dev: network device
 275  *
 276  * Device has detected loss of carrier.
 277  */
 278 void netif_carrier_off(struct net_device *dev)
 279 {
 280         if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
 281                 linkwatch_fire_event(dev);
 282 }
 283 EXPORT_SYMBOL(netif_carrier_off);
 284
 285 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
 286    under all circumstances. It is difficult to invent anything faster or
 287    cheaper.
 288  */
 289
 290 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
 291 {
 292         kfree_skb(skb);
 293         return NET_XMIT_CN;
 294 }
 295
 296 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
 297 {
 298         return NULL;
 299 }
 300
 301 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 302 {
 303         if (net_ratelimit())
 304                 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
 305                        skb->dev->name);
 306         kfree_skb(skb);
 307         return NET_XMIT_CN;
 308 }
 309
 310 struct Qdisc_ops noop_qdisc_ops __read_mostly = {
 311         .id             =       "noop",
 312         .priv_size      =       0,
 313         .enqueue        =       noop_enqueue,
 314         .dequeue        =       noop_dequeue,
 315         .requeue        =       noop_requeue,
 316         .owner          =       THIS_MODULE,
 317 };
 318
 319 static struct netdev_queue noop_netdev_queue = {
 320         .qdisc          =       &noop_qdisc,
 321 };
 322
 323 struct Qdisc noop_qdisc = {
 324         .enqueue        =       noop_enqueue,
 325         .dequeue        =       noop_dequeue,
 326         .flags          =       TCQ_F_BUILTIN,
 327         .ops            =       &noop_qdisc_ops,
 328         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
 329         .q.lock         =       __SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
 330         .dev_queue      =       &noop_netdev_queue,
 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 int fifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 353 {
 354         struct sk_buff_head *list = &qdisc->q;
 355
 356         if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len)
 357                 return __qdisc_enqueue_tail(skb, qdisc, list);
 358
 359         return qdisc_drop(skb, qdisc);
 360 }
 361
 362 static struct sk_buff *fifo_fast_dequeue(struct Qdisc* qdisc)
 363 {
 364         struct sk_buff_head *list = &qdisc->q;
 365
 366         if (!skb_queue_empty(list))
 367                 return __qdisc_dequeue_head(qdisc, list);
 368
 369         return NULL;
 370 }
 371
 372 static int fifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 373 {
 374         return __qdisc_requeue(skb, qdisc, &qdisc->q);
 375 }
 376
 377 static void fifo_fast_reset(struct Qdisc* qdisc)
 378 {
 379         __qdisc_reset_queue(qdisc, &qdisc->q);
 380         qdisc->qstats.backlog = 0;
 381 }
 382
 383 static struct Qdisc_ops fifo_fast_ops __read_mostly = {
 384         .id             =       "fifo_fast",
 385         .priv_size      =       0,
 386         .enqueue        =       fifo_fast_enqueue,
 387         .dequeue        =       fifo_fast_dequeue,
 388         .requeue        =       fifo_fast_requeue,
 389         .reset          =       fifo_fast_reset,
 390         .owner          =       THIS_MODULE,
 391 };
 392
 393 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 394                           struct Qdisc_ops *ops)
 395 {
 396         void *p;
 397         struct Qdisc *sch;
 398         unsigned int size;
 399         int err = -ENOBUFS;
 400
 401         /* ensure that the Qdisc and the private data are 32-byte aligned */
 402         size = QDISC_ALIGN(sizeof(*sch));
 403         size += ops->priv_size + (QDISC_ALIGNTO - 1);
 404
 405         p = kzalloc(size, GFP_KERNEL);
 406         if (!p)
 407                 goto errout;
 408         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
 409         sch->padded = (char *) sch - (char *) p;
 410
 411         INIT_LIST_HEAD(&sch->list);
 412         skb_queue_head_init(&sch->q);
 413         sch->ops = ops;
 414         sch->enqueue = ops->enqueue;
 415         sch->dequeue = ops->dequeue;
 416         sch->dev_queue = dev_queue;
 417         dev_hold(qdisc_dev(sch));
 418         atomic_set(&sch->refcnt, 1);
 419
 420         return sch;
 421 errout:
 422         return ERR_PTR(err);
 423 }
 424
 425 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
 426                                  struct netdev_queue *dev_queue,
 427                                  struct Qdisc_ops *ops,
 428                                  unsigned int parentid)
 429 {
 430         struct Qdisc *sch;
 431
 432         sch = qdisc_alloc(dev_queue, ops);
 433         if (IS_ERR(sch))
 434                 goto errout;
 435         sch->parent = parentid;
 436
 437         if (!ops->init || ops->init(sch, NULL) == 0)
 438                 return sch;
 439
 440         qdisc_destroy(sch);
 441 errout:
 442         return NULL;
 443 }
 444 EXPORT_SYMBOL(qdisc_create_dflt);
 445
 446 /* Under qdisc_root_lock(qdisc) and BH! */
 447
 448 void qdisc_reset(struct Qdisc *qdisc)
 449 {
 450         const struct Qdisc_ops *ops = qdisc->ops;
 451
 452         if (ops->reset)
 453                 ops->reset(qdisc);
 454 }
 455 EXPORT_SYMBOL(qdisc_reset);
 456
 457 /* this is the rcu callback function to clean up a qdisc when there
 458  * are no further references to it */
 459
 460 static void __qdisc_destroy(struct rcu_head *head)
 461 {
 462         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
 463         const struct Qdisc_ops  *ops = qdisc->ops;
 464
 465         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
 466         if (ops->reset)
 467                 ops->reset(qdisc);
 468         if (ops->destroy)
 469                 ops->destroy(qdisc);
 470
 471         module_put(ops->owner);
 472         dev_put(qdisc_dev(qdisc));
 473
 474         kfree_skb(qdisc->gso_skb);
 475
 476         kfree((char *) qdisc - qdisc->padded);
 477 }
 478
 479 /* Under qdisc_root_lock(qdisc) and BH! */
 480
 481 void qdisc_destroy(struct Qdisc *qdisc)
 482 {
 483         struct net_device *dev = qdisc_dev(qdisc);
 484
 485         if (qdisc->flags & TCQ_F_BUILTIN ||
 486             !atomic_dec_and_test(&qdisc->refcnt))
 487                 return;
 488
 489         spin_lock_bh(&dev->qdisc_list_lock);
 490         list_del(&qdisc->list);
 491         spin_unlock_bh(&dev->qdisc_list_lock);
 492
 493         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
 494 }
 495 EXPORT_SYMBOL(qdisc_destroy);
 496
 497 static bool dev_all_qdisc_sleeping_noop(struct net_device *dev)
 498 {
 499         unsigned int i;
 500
 501         for (i = 0; i < dev->num_tx_queues; i++) {
 502                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
 503
 504                 if (txq->qdisc_sleeping != &noop_qdisc)
 505                         return false;
 506         }
 507         return true;
 508 }
 509
 510 static void attach_one_default_qdisc(struct net_device *dev,
 511                                      struct netdev_queue *dev_queue,
 512                                      void *_unused)
 513 {
 514         struct Qdisc *qdisc;
 515
 516         if (dev->tx_queue_len) {
 517                 qdisc = qdisc_create_dflt(dev, dev_queue,
 518                                           &fifo_fast_ops, TC_H_ROOT);
 519                 if (!qdisc) {
 520                         printk(KERN_INFO "%s: activation failed\n", dev->name);
 521                         return;
 522                 }
 523                 spin_lock_bh(&dev->qdisc_list_lock);
 524                 list_add_tail(&qdisc->list, &dev->qdisc_list);
 525                 spin_unlock_bh(&dev->qdisc_list_lock);
 526         } else {
 527                 qdisc =  &noqueue_qdisc;
 528         }
 529         dev_queue->qdisc_sleeping = qdisc;
 530 }
 531
 532 static void transition_one_qdisc(struct net_device *dev,
 533                                  struct netdev_queue *dev_queue,
 534                                  void *_need_watchdog)
 535 {
 536         struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
 537         int *need_watchdog_p = _need_watchdog;
 538
 539         rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
 540         if (new_qdisc != &noqueue_qdisc)
 541                 *need_watchdog_p = 1;
 542 }
 543
 544 void dev_activate(struct net_device *dev)
 545 {
 546         int need_watchdog;
 547
 548         /* No queueing discipline is attached to device;
 549          * create default one i.e. fifo_fast for devices,
 550          * which need queueing and noqueue_qdisc for
 551          * virtual interfaces.
 552          */
 553
 554         if (dev_all_qdisc_sleeping_noop(dev))
 555                 netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
 556
 557         if (!netif_carrier_ok(dev))
 558                 /* Delay activation until next carrier-on event */
 559                 return;
 560
 561         need_watchdog = 0;
 562         netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
 563
 564         if (need_watchdog) {
 565                 dev->trans_start = jiffies;
 566                 dev_watchdog_up(dev);
 567         }
 568 }
 569
 570 static void dev_deactivate_queue(struct net_device *dev,
 571                                  struct netdev_queue *dev_queue,
 572                                  void *_qdisc_default)
 573 {
 574         struct Qdisc *qdisc_default = _qdisc_default;
 575         struct sk_buff *skb = NULL;
 576         struct Qdisc *qdisc;
 577
 578         qdisc = dev_queue->qdisc;
 579         if (qdisc) {
 580                 spin_lock_bh(qdisc_lock(qdisc));
 581
 582                 dev_queue->qdisc = qdisc_default;
 583                 qdisc_reset(qdisc);
 584
 585                 spin_unlock_bh(qdisc_lock(qdisc));
 586         }
 587
 588         kfree_skb(skb);
 589 }
 590
 591 static bool some_qdisc_is_running(struct net_device *dev, int lock)
 592 {
 593         unsigned int i;
 594
 595         for (i = 0; i < dev->num_tx_queues; i++) {
 596                 struct netdev_queue *dev_queue;
 597                 spinlock_t *root_lock;
 598                 struct Qdisc *q;
 599                 int val;
 600
 601                 dev_queue = netdev_get_tx_queue(dev, i);
 602                 q = dev_queue->qdisc;
 603                 root_lock = qdisc_root_lock(q);
 604
 605                 if (lock)
 606                         spin_lock_bh(root_lock);
 607
 608                 val = test_bit(__QDISC_STATE_RUNNING, &q->state);
 609
 610                 if (lock)
 611                         spin_unlock_bh(root_lock);
 612
 613                 if (val)
 614                         return true;
 615         }
 616         return false;
 617 }
 618
 619 void dev_deactivate(struct net_device *dev)
 620 {
 621         bool running;
 622
 623         netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
 624
 625         dev_watchdog_down(dev);
 626
 627         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
 628         synchronize_rcu();
 629
 630         /* Wait for outstanding qdisc_run calls. */
 631         do {
 632                 while (some_qdisc_is_running(dev, 0))
 633                         yield();
 634
 635                 /*
 636                  * Double-check inside queue lock to ensure that all effects
 637                  * of the queue run are visible when we return.
 638                  */
 639                 running = some_qdisc_is_running(dev, 1);
 640
 641                 /*
 642                  * The running flag should never be set at this point because
 643                  * we've already set dev->qdisc to noop_qdisc *inside* the same
 644                  * pair of spin locks.  That is, if any qdisc_run starts after
 645                  * our initial test it should see the noop_qdisc and then
 646                  * clear the RUNNING bit before dropping the queue lock.  So
 647                  * if it is set here then we've found a bug.
 648                  */
 649         } while (WARN_ON_ONCE(running));
 650 }
 651
 652 static void dev_init_scheduler_queue(struct net_device *dev,
 653                                      struct netdev_queue *dev_queue,
 654                                      void *_qdisc)
 655 {
 656         struct Qdisc *qdisc = _qdisc;
 657
 658         dev_queue->qdisc = qdisc;
 659         dev_queue->qdisc_sleeping = qdisc;
 660 }
 661
 662 void dev_init_scheduler(struct net_device *dev)
 663 {
 664         netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
 665         dev_init_scheduler_queue(dev, &dev->rx_queue, NULL);
 666
 667         setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
 668 }
 669
 670 static void shutdown_scheduler_queue(struct net_device *dev,
 671                                      struct netdev_queue *dev_queue,
 672                                      void *_qdisc_default)
 673 {
 674         struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
 675         struct Qdisc *qdisc_default = _qdisc_default;
 676
 677         if (qdisc) {
 678                 spinlock_t *root_lock = qdisc_root_lock(qdisc);
 679
 680                 dev_queue->qdisc = qdisc_default;
 681                 dev_queue->qdisc_sleeping = qdisc_default;
 682
 683                 spin_lock(root_lock);
 684                 qdisc_destroy(qdisc);
 685                 spin_unlock(root_lock);
 686         }
 687 }
 688
 689 void dev_shutdown(struct net_device *dev)
 690 {
 691         netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
 692         shutdown_scheduler_queue(dev, &dev->rx_queue, NULL);
 693         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
 694 }