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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  * 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 static struct netdev_queue noqueue_netdev_queue = {
 345         .qdisc          =       &noqueue_qdisc,
 346 };
 347
 348 static struct Qdisc noqueue_qdisc = {
 349         .enqueue        =       NULL,
 350         .dequeue        =       noop_dequeue,
 351         .flags          =       TCQ_F_BUILTIN,
 352         .ops            =       &noqueue_qdisc_ops,
 353         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
 354         .q.lock         =       __SPIN_LOCK_UNLOCKED(noqueue_qdisc.q.lock),
 355         .dev_queue      =       &noqueue_netdev_queue,
 356 };
 357
 358
 359 static const u8 prio2band[TC_PRIO_MAX+1] =
 360         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
 361
 362 /* 3-band FIFO queue: old style, but should be a bit faster than
 363    generic prio+fifo combination.
 364  */
 365
 366 #define PFIFO_FAST_BANDS 3
 367
 368 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
 369                                              struct Qdisc *qdisc)
 370 {
 371         struct sk_buff_head *list = qdisc_priv(qdisc);
 372         return list + prio2band[skb->priority & TC_PRIO_MAX];
 373 }
 374
 375 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 376 {
 377         struct sk_buff_head *list = prio2list(skb, qdisc);
 378
 379         if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len) {
 380                 qdisc->q.qlen++;
 381                 return __qdisc_enqueue_tail(skb, qdisc, list);
 382         }
 383
 384         return qdisc_drop(skb, qdisc);
 385 }
 386
 387 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
 388 {
 389         int prio;
 390         struct sk_buff_head *list = qdisc_priv(qdisc);
 391
 392         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
 393                 if (!skb_queue_empty(list + prio)) {
 394                         qdisc->q.qlen--;
 395                         return __qdisc_dequeue_head(qdisc, list + prio);
 396                 }
 397         }
 398
 399         return NULL;
 400 }
 401
 402 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 403 {
 404         qdisc->q.qlen++;
 405         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
 406 }
 407
 408 static void pfifo_fast_reset(struct Qdisc* qdisc)
 409 {
 410         int prio;
 411         struct sk_buff_head *list = qdisc_priv(qdisc);
 412
 413         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 414                 __qdisc_reset_queue(qdisc, list + prio);
 415
 416         qdisc->qstats.backlog = 0;
 417         qdisc->q.qlen = 0;
 418 }
 419
 420 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
 421 {
 422         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
 423
 424         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
 425         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 426         return skb->len;
 427
 428 nla_put_failure:
 429         return -1;
 430 }
 431
 432 static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
 433 {
 434         int prio;
 435         struct sk_buff_head *list = qdisc_priv(qdisc);
 436
 437         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 438                 skb_queue_head_init(list + prio);
 439
 440         return 0;
 441 }
 442
 443 static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
 444         .id             =       "pfifo_fast",
 445         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
 446         .enqueue        =       pfifo_fast_enqueue,
 447         .dequeue        =       pfifo_fast_dequeue,
 448         .requeue        =       pfifo_fast_requeue,
 449         .init           =       pfifo_fast_init,
 450         .reset          =       pfifo_fast_reset,
 451         .dump           =       pfifo_fast_dump,
 452         .owner          =       THIS_MODULE,
 453 };
 454
 455 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 456                           struct Qdisc_ops *ops)
 457 {
 458         void *p;
 459         struct Qdisc *sch;
 460         unsigned int size;
 461         int err = -ENOBUFS;
 462
 463         /* ensure that the Qdisc and the private data are 32-byte aligned */
 464         size = QDISC_ALIGN(sizeof(*sch));
 465         size += ops->priv_size + (QDISC_ALIGNTO - 1);
 466
 467         p = kzalloc(size, GFP_KERNEL);
 468         if (!p)
 469                 goto errout;
 470         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
 471         sch->padded = (char *) sch - (char *) p;
 472
 473         INIT_LIST_HEAD(&sch->list);
 474         skb_queue_head_init(&sch->q);
 475         sch->ops = ops;
 476         sch->enqueue = ops->enqueue;
 477         sch->dequeue = ops->dequeue;
 478         sch->dev_queue = dev_queue;
 479         dev_hold(qdisc_dev(sch));
 480         atomic_set(&sch->refcnt, 1);
 481
 482         return sch;
 483 errout:
 484         return ERR_PTR(err);
 485 }
 486
 487 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
 488                                  struct netdev_queue *dev_queue,
 489                                  struct Qdisc_ops *ops,
 490                                  unsigned int parentid)
 491 {
 492         struct Qdisc *sch;
 493
 494         sch = qdisc_alloc(dev_queue, ops);
 495         if (IS_ERR(sch))
 496                 goto errout;
 497         sch->parent = parentid;
 498
 499         if (!ops->init || ops->init(sch, NULL) == 0)
 500                 return sch;
 501
 502         qdisc_destroy(sch);
 503 errout:
 504         return NULL;
 505 }
 506 EXPORT_SYMBOL(qdisc_create_dflt);
 507
 508 /* Under qdisc_root_lock(qdisc) and BH! */
 509
 510 void qdisc_reset(struct Qdisc *qdisc)
 511 {
 512         const struct Qdisc_ops *ops = qdisc->ops;
 513
 514         if (ops->reset)
 515                 ops->reset(qdisc);
 516 }
 517 EXPORT_SYMBOL(qdisc_reset);
 518
 519 /* this is the rcu callback function to clean up a qdisc when there
 520  * are no further references to it */
 521
 522 static void __qdisc_destroy(struct rcu_head *head)
 523 {
 524         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
 525         const struct Qdisc_ops  *ops = qdisc->ops;
 526
 527 #ifdef CONFIG_NET_SCHED
 528         qdisc_put_stab(qdisc->stab);
 529 #endif
 530         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
 531         if (ops->reset)
 532                 ops->reset(qdisc);
 533         if (ops->destroy)
 534                 ops->destroy(qdisc);
 535
 536         module_put(ops->owner);
 537         dev_put(qdisc_dev(qdisc));
 538
 539         kfree_skb(qdisc->gso_skb);
 540
 541         kfree((char *) qdisc - qdisc->padded);
 542 }
 543
 544 /* Under qdisc_root_lock(qdisc) and BH! */
 545
 546 void qdisc_destroy(struct Qdisc *qdisc)
 547 {
 548         if (qdisc->flags & TCQ_F_BUILTIN ||
 549             !atomic_dec_and_test(&qdisc->refcnt))
 550                 return;
 551
 552         if (qdisc->parent)
 553                 list_del(&qdisc->list);
 554
 555         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
 556 }
 557 EXPORT_SYMBOL(qdisc_destroy);
 558
 559 static bool dev_all_qdisc_sleeping_noop(struct net_device *dev)
 560 {
 561         unsigned int i;
 562
 563         for (i = 0; i < dev->num_tx_queues; i++) {
 564                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
 565
 566                 if (txq->qdisc_sleeping != &noop_qdisc)
 567                         return false;
 568         }
 569         return true;
 570 }
 571
 572 static void attach_one_default_qdisc(struct net_device *dev,
 573                                      struct netdev_queue *dev_queue,
 574                                      void *_unused)
 575 {
 576         struct Qdisc *qdisc;
 577
 578         if (dev->tx_queue_len) {
 579                 qdisc = qdisc_create_dflt(dev, dev_queue,
 580                                           &pfifo_fast_ops, TC_H_ROOT);
 581                 if (!qdisc) {
 582                         printk(KERN_INFO "%s: activation failed\n", dev->name);
 583                         return;
 584                 }
 585         } else {
 586                 qdisc =  &noqueue_qdisc;
 587         }
 588         dev_queue->qdisc_sleeping = qdisc;
 589 }
 590
 591 static void transition_one_qdisc(struct net_device *dev,
 592                                  struct netdev_queue *dev_queue,
 593                                  void *_need_watchdog)
 594 {
 595         struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
 596         int *need_watchdog_p = _need_watchdog;
 597
 598         rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
 599         if (new_qdisc != &noqueue_qdisc)
 600                 *need_watchdog_p = 1;
 601 }
 602
 603 void dev_activate(struct net_device *dev)
 604 {
 605         int need_watchdog;
 606
 607         /* No queueing discipline is attached to device;
 608            create default one i.e. pfifo_fast for devices,
 609            which need queueing and noqueue_qdisc for
 610            virtual interfaces
 611          */
 612
 613         if (dev_all_qdisc_sleeping_noop(dev))
 614                 netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
 615
 616         if (!netif_carrier_ok(dev))
 617                 /* Delay activation until next carrier-on event */
 618                 return;
 619
 620         need_watchdog = 0;
 621         netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
 622
 623         if (need_watchdog) {
 624                 dev->trans_start = jiffies;
 625                 dev_watchdog_up(dev);
 626         }
 627 }
 628
 629 static void dev_deactivate_queue(struct net_device *dev,
 630                                  struct netdev_queue *dev_queue,
 631                                  void *_qdisc_default)
 632 {
 633         struct Qdisc *qdisc_default = _qdisc_default;
 634         struct Qdisc *qdisc;
 635
 636         qdisc = dev_queue->qdisc;
 637         if (qdisc) {
 638                 spin_lock_bh(qdisc_lock(qdisc));
 639
 640                 dev_queue->qdisc = qdisc_default;
 641                 qdisc_reset(qdisc);
 642
 643                 spin_unlock_bh(qdisc_lock(qdisc));
 644         }
 645 }
 646
 647 static bool some_qdisc_is_running(struct net_device *dev, int lock)
 648 {
 649         unsigned int i;
 650
 651         for (i = 0; i < dev->num_tx_queues; i++) {
 652                 struct netdev_queue *dev_queue;
 653                 spinlock_t *root_lock;
 654                 struct Qdisc *q;
 655                 int val;
 656
 657                 dev_queue = netdev_get_tx_queue(dev, i);
 658                 q = dev_queue->qdisc;
 659                 root_lock = qdisc_root_lock(q);
 660
 661                 if (lock)
 662                         spin_lock_bh(root_lock);
 663
 664                 val = test_bit(__QDISC_STATE_RUNNING, &q->state);
 665
 666                 if (lock)
 667                         spin_unlock_bh(root_lock);
 668
 669                 if (val)
 670                         return true;
 671         }
 672         return false;
 673 }
 674
 675 void dev_deactivate(struct net_device *dev)
 676 {
 677         bool running;
 678
 679         netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
 680
 681         dev_watchdog_down(dev);
 682
 683         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
 684         synchronize_rcu();
 685
 686         /* Wait for outstanding qdisc_run calls. */
 687         do {
 688                 while (some_qdisc_is_running(dev, 0))
 689                         yield();
 690
 691                 /*
 692                  * Double-check inside queue lock to ensure that all effects
 693                  * of the queue run are visible when we return.
 694                  */
 695                 running = some_qdisc_is_running(dev, 1);
 696
 697                 /*
 698                  * The running flag should never be set at this point because
 699                  * we've already set dev->qdisc to noop_qdisc *inside* the same
 700                  * pair of spin locks.  That is, if any qdisc_run starts after
 701                  * our initial test it should see the noop_qdisc and then
 702                  * clear the RUNNING bit before dropping the queue lock.  So
 703                  * if it is set here then we've found a bug.
 704                  */
 705         } while (WARN_ON_ONCE(running));
 706 }
 707
 708 static void dev_init_scheduler_queue(struct net_device *dev,
 709                                      struct netdev_queue *dev_queue,
 710                                      void *_qdisc)
 711 {
 712         struct Qdisc *qdisc = _qdisc;
 713
 714         dev_queue->qdisc = qdisc;
 715         dev_queue->qdisc_sleeping = qdisc;
 716 }
 717
 718 void dev_init_scheduler(struct net_device *dev)
 719 {
 720         netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
 721         dev_init_scheduler_queue(dev, &dev->rx_queue, NULL);
 722
 723         setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
 724 }
 725
 726 static void shutdown_scheduler_queue(struct net_device *dev,
 727                                      struct netdev_queue *dev_queue,
 728                                      void *_qdisc_default)
 729 {
 730         struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
 731         struct Qdisc *qdisc_default = _qdisc_default;
 732
 733         if (qdisc) {
 734                 spinlock_t *root_lock = qdisc_root_lock(qdisc);
 735
 736                 dev_queue->qdisc = qdisc_default;
 737                 dev_queue->qdisc_sleeping = qdisc_default;
 738
 739                 spin_lock(root_lock);
 740                 qdisc_destroy(qdisc);
 741                 spin_unlock(root_lock);
 742         }
 743 }
 744
 745 void dev_shutdown(struct net_device *dev)
 746 {
 747         netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
 748         shutdown_scheduler_queue(dev, &dev->rx_queue, NULL);
 749         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
 750 }