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