warn: Turn the netdev timeout WARN_ON() into a WARN()
[linux-2.6.git] / 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_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_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_tx_queue_stopped(txq) &&
139             !netif_tx_queue_frozen(txq))
140                 ret = dev_hard_start_xmit(skb, dev, txq);
141         HARD_TX_UNLOCK(dev, txq);
142
143         spin_lock(root_lock);
144
145         switch (ret) {
146         case NETDEV_TX_OK:
147                 /* Driver sent out skb successfully */
148                 ret = qdisc_qlen(q);
149                 break;
150
151         case NETDEV_TX_LOCKED:
152                 /* Driver try lock failed */
153                 ret = handle_dev_cpu_collision(skb, txq, q);
154                 break;
155
156         default:
157                 /* Driver returned NETDEV_TX_BUSY - requeue skb */
158                 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
159                         printk(KERN_WARNING "BUG %s code %d qlen %d\n",
160                                dev->name, ret, q->q.qlen);
161
162                 ret = dev_requeue_skb(skb, q);
163                 break;
164         }
165
166         if (ret && (netif_tx_queue_stopped(txq) ||
167                     netif_tx_queue_frozen(txq)))
168                 ret = 0;
169
170         return ret;
171 }
172
173 void __qdisc_run(struct Qdisc *q)
174 {
175         unsigned long start_time = jiffies;
176
177         while (qdisc_restart(q)) {
178                 /*
179                  * Postpone processing if
180                  * 1. another process needs the CPU;
181                  * 2. we've been doing it for too long.
182                  */
183                 if (need_resched() || jiffies != start_time) {
184                         __netif_schedule(q);
185                         break;
186                 }
187         }
188
189         clear_bit(__QDISC_STATE_RUNNING, &q->state);
190 }
191
192 static void dev_watchdog(unsigned long arg)
193 {
194         struct net_device *dev = (struct net_device *)arg;
195
196         netif_tx_lock(dev);
197         if (!qdisc_tx_is_noop(dev)) {
198                 if (netif_device_present(dev) &&
199                     netif_running(dev) &&
200                     netif_carrier_ok(dev)) {
201                         int some_queue_stopped = 0;
202                         unsigned int i;
203
204                         for (i = 0; i < dev->num_tx_queues; i++) {
205                                 struct netdev_queue *txq;
206
207                                 txq = netdev_get_tx_queue(dev, i);
208                                 if (netif_tx_queue_stopped(txq)) {
209                                         some_queue_stopped = 1;
210                                         break;
211                                 }
212                         }
213
214                         if (some_queue_stopped &&
215                             time_after(jiffies, (dev->trans_start +
216                                                  dev->watchdog_timeo))) {
217                                 char drivername[64];
218                                 WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit timed out\n",
219                                        dev->name, netdev_drivername(dev, drivername, 64));
220                                 dev->tx_timeout(dev);
221                         }
222                         if (!mod_timer(&dev->watchdog_timer,
223                                        round_jiffies(jiffies +
224                                                      dev->watchdog_timeo)))
225                                 dev_hold(dev);
226                 }
227         }
228         netif_tx_unlock(dev);
229
230         dev_put(dev);
231 }
232
233 void __netdev_watchdog_up(struct net_device *dev)
234 {
235         if (dev->tx_timeout) {
236                 if (dev->watchdog_timeo <= 0)
237                         dev->watchdog_timeo = 5*HZ;
238                 if (!mod_timer(&dev->watchdog_timer,
239                                round_jiffies(jiffies + dev->watchdog_timeo)))
240                         dev_hold(dev);
241         }
242 }
243
244 static void dev_watchdog_up(struct net_device *dev)
245 {
246         __netdev_watchdog_up(dev);
247 }
248
249 static void dev_watchdog_down(struct net_device *dev)
250 {
251         netif_tx_lock_bh(dev);
252         if (del_timer(&dev->watchdog_timer))
253                 dev_put(dev);
254         netif_tx_unlock_bh(dev);
255 }
256
257 /**
258  *      netif_carrier_on - set carrier
259  *      @dev: network device
260  *
261  * Device has detected that carrier.
262  */
263 void netif_carrier_on(struct net_device *dev)
264 {
265         if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
266                 linkwatch_fire_event(dev);
267                 if (netif_running(dev))
268                         __netdev_watchdog_up(dev);
269         }
270 }
271 EXPORT_SYMBOL(netif_carrier_on);
272
273 /**
274  *      netif_carrier_off - clear carrier
275  *      @dev: network device
276  *
277  * Device has detected loss of carrier.
278  */
279 void netif_carrier_off(struct net_device *dev)
280 {
281         if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
282                 linkwatch_fire_event(dev);
283 }
284 EXPORT_SYMBOL(netif_carrier_off);
285
286 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
287    under all circumstances. It is difficult to invent anything faster or
288    cheaper.
289  */
290
291 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
292 {
293         kfree_skb(skb);
294         return NET_XMIT_CN;
295 }
296
297 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
298 {
299         return NULL;
300 }
301
302 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
303 {
304         if (net_ratelimit())
305                 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
306                        skb->dev->name);
307         kfree_skb(skb);
308         return NET_XMIT_CN;
309 }
310
311 struct Qdisc_ops noop_qdisc_ops __read_mostly = {
312         .id             =       "noop",
313         .priv_size      =       0,
314         .enqueue        =       noop_enqueue,
315         .dequeue        =       noop_dequeue,
316         .requeue        =       noop_requeue,
317         .owner          =       THIS_MODULE,
318 };
319
320 static struct netdev_queue noop_netdev_queue = {
321         .qdisc          =       &noop_qdisc,
322 };
323
324 struct Qdisc noop_qdisc = {
325         .enqueue        =       noop_enqueue,
326         .dequeue        =       noop_dequeue,
327         .flags          =       TCQ_F_BUILTIN,
328         .ops            =       &noop_qdisc_ops,
329         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
330         .q.lock         =       __SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
331         .dev_queue      =       &noop_netdev_queue,
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 static struct netdev_queue noqueue_netdev_queue = {
346         .qdisc          =       &noqueue_qdisc,
347 };
348
349 static struct Qdisc noqueue_qdisc = {
350         .enqueue        =       NULL,
351         .dequeue        =       noop_dequeue,
352         .flags          =       TCQ_F_BUILTIN,
353         .ops            =       &noqueue_qdisc_ops,
354         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
355         .q.lock         =       __SPIN_LOCK_UNLOCKED(noqueue_qdisc.q.lock),
356         .dev_queue      =       &noqueue_netdev_queue,
357 };
358
359
360 static const u8 prio2band[TC_PRIO_MAX+1] =
361         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
362
363 /* 3-band FIFO queue: old style, but should be a bit faster than
364    generic prio+fifo combination.
365  */
366
367 #define PFIFO_FAST_BANDS 3
368
369 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
370                                              struct Qdisc *qdisc)
371 {
372         struct sk_buff_head *list = qdisc_priv(qdisc);
373         return list + prio2band[skb->priority & TC_PRIO_MAX];
374 }
375
376 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
377 {
378         struct sk_buff_head *list = prio2list(skb, qdisc);
379
380         if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len) {
381                 qdisc->q.qlen++;
382                 return __qdisc_enqueue_tail(skb, qdisc, list);
383         }
384
385         return qdisc_drop(skb, qdisc);
386 }
387
388 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
389 {
390         int prio;
391         struct sk_buff_head *list = qdisc_priv(qdisc);
392
393         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
394                 if (!skb_queue_empty(list + prio)) {
395                         qdisc->q.qlen--;
396                         return __qdisc_dequeue_head(qdisc, list + prio);
397                 }
398         }
399
400         return NULL;
401 }
402
403 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
404 {
405         qdisc->q.qlen++;
406         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
407 }
408
409 static void pfifo_fast_reset(struct Qdisc* qdisc)
410 {
411         int prio;
412         struct sk_buff_head *list = qdisc_priv(qdisc);
413
414         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
415                 __qdisc_reset_queue(qdisc, list + prio);
416
417         qdisc->qstats.backlog = 0;
418         qdisc->q.qlen = 0;
419 }
420
421 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
422 {
423         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
424
425         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
426         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
427         return skb->len;
428
429 nla_put_failure:
430         return -1;
431 }
432
433 static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
434 {
435         int prio;
436         struct sk_buff_head *list = qdisc_priv(qdisc);
437
438         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
439                 skb_queue_head_init(list + prio);
440
441         return 0;
442 }
443
444 static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
445         .id             =       "pfifo_fast",
446         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
447         .enqueue        =       pfifo_fast_enqueue,
448         .dequeue        =       pfifo_fast_dequeue,
449         .requeue        =       pfifo_fast_requeue,
450         .init           =       pfifo_fast_init,
451         .reset          =       pfifo_fast_reset,
452         .dump           =       pfifo_fast_dump,
453         .owner          =       THIS_MODULE,
454 };
455
456 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
457                           struct Qdisc_ops *ops)
458 {
459         void *p;
460         struct Qdisc *sch;
461         unsigned int size;
462         int err = -ENOBUFS;
463
464         /* ensure that the Qdisc and the private data are 32-byte aligned */
465         size = QDISC_ALIGN(sizeof(*sch));
466         size += ops->priv_size + (QDISC_ALIGNTO - 1);
467
468         p = kzalloc(size, GFP_KERNEL);
469         if (!p)
470                 goto errout;
471         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
472         sch->padded = (char *) sch - (char *) p;
473
474         INIT_LIST_HEAD(&sch->list);
475         skb_queue_head_init(&sch->q);
476         sch->ops = ops;
477         sch->enqueue = ops->enqueue;
478         sch->dequeue = ops->dequeue;
479         sch->dev_queue = dev_queue;
480         dev_hold(qdisc_dev(sch));
481         atomic_set(&sch->refcnt, 1);
482
483         return sch;
484 errout:
485         return ERR_PTR(err);
486 }
487
488 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
489                                  struct netdev_queue *dev_queue,
490                                  struct Qdisc_ops *ops,
491                                  unsigned int parentid)
492 {
493         struct Qdisc *sch;
494
495         sch = qdisc_alloc(dev_queue, ops);
496         if (IS_ERR(sch))
497                 goto errout;
498         sch->parent = parentid;
499
500         if (!ops->init || ops->init(sch, NULL) == 0)
501                 return sch;
502
503         qdisc_destroy(sch);
504 errout:
505         return NULL;
506 }
507 EXPORT_SYMBOL(qdisc_create_dflt);
508
509 /* Under qdisc_lock(qdisc) and BH! */
510
511 void qdisc_reset(struct Qdisc *qdisc)
512 {
513         const struct Qdisc_ops *ops = qdisc->ops;
514
515         if (ops->reset)
516                 ops->reset(qdisc);
517 }
518 EXPORT_SYMBOL(qdisc_reset);
519
520 void qdisc_destroy(struct Qdisc *qdisc)
521 {
522         const struct Qdisc_ops  *ops = qdisc->ops;
523
524         if (qdisc->flags & TCQ_F_BUILTIN ||
525             !atomic_dec_and_test(&qdisc->refcnt))
526                 return;
527
528 #ifdef CONFIG_NET_SCHED
529         qdisc_list_del(qdisc);
530
531         qdisc_put_stab(qdisc->stab);
532 #endif
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
542         kfree_skb(qdisc->gso_skb);
543
544         kfree((char *) qdisc - qdisc->padded);
545 }
546 EXPORT_SYMBOL(qdisc_destroy);
547
548 static bool dev_all_qdisc_sleeping_noop(struct net_device *dev)
549 {
550         unsigned int i;
551
552         for (i = 0; i < dev->num_tx_queues; i++) {
553                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
554
555                 if (txq->qdisc_sleeping != &noop_qdisc)
556                         return false;
557         }
558         return true;
559 }
560
561 static void attach_one_default_qdisc(struct net_device *dev,
562                                      struct netdev_queue *dev_queue,
563                                      void *_unused)
564 {
565         struct Qdisc *qdisc;
566
567         if (dev->tx_queue_len) {
568                 qdisc = qdisc_create_dflt(dev, dev_queue,
569                                           &pfifo_fast_ops, TC_H_ROOT);
570                 if (!qdisc) {
571                         printk(KERN_INFO "%s: activation failed\n", dev->name);
572                         return;
573                 }
574         } else {
575                 qdisc =  &noqueue_qdisc;
576         }
577         dev_queue->qdisc_sleeping = qdisc;
578 }
579
580 static void transition_one_qdisc(struct net_device *dev,
581                                  struct netdev_queue *dev_queue,
582                                  void *_need_watchdog)
583 {
584         struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
585         int *need_watchdog_p = _need_watchdog;
586
587         if (!(new_qdisc->flags & TCQ_F_BUILTIN))
588                 clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
589
590         rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
591         if (need_watchdog_p && new_qdisc != &noqueue_qdisc)
592                 *need_watchdog_p = 1;
593 }
594
595 void dev_activate(struct net_device *dev)
596 {
597         int need_watchdog;
598
599         /* No queueing discipline is attached to device;
600            create default one i.e. pfifo_fast for devices,
601            which need queueing and noqueue_qdisc for
602            virtual interfaces
603          */
604
605         if (dev_all_qdisc_sleeping_noop(dev))
606                 netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
607
608         if (!netif_carrier_ok(dev))
609                 /* Delay activation until next carrier-on event */
610                 return;
611
612         need_watchdog = 0;
613         netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
614         transition_one_qdisc(dev, &dev->rx_queue, NULL);
615
616         if (need_watchdog) {
617                 dev->trans_start = jiffies;
618                 dev_watchdog_up(dev);
619         }
620 }
621
622 static void dev_deactivate_queue(struct net_device *dev,
623                                  struct netdev_queue *dev_queue,
624                                  void *_qdisc_default)
625 {
626         struct Qdisc *qdisc_default = _qdisc_default;
627         struct Qdisc *qdisc;
628
629         qdisc = dev_queue->qdisc;
630         if (qdisc) {
631                 spin_lock_bh(qdisc_lock(qdisc));
632
633                 if (!(qdisc->flags & TCQ_F_BUILTIN))
634                         set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
635
636                 rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
637                 qdisc_reset(qdisc);
638
639                 spin_unlock_bh(qdisc_lock(qdisc));
640         }
641 }
642
643 static bool some_qdisc_is_busy(struct net_device *dev)
644 {
645         unsigned int i;
646
647         for (i = 0; i < dev->num_tx_queues; i++) {
648                 struct netdev_queue *dev_queue;
649                 spinlock_t *root_lock;
650                 struct Qdisc *q;
651                 int val;
652
653                 dev_queue = netdev_get_tx_queue(dev, i);
654                 q = dev_queue->qdisc_sleeping;
655                 root_lock = qdisc_lock(q);
656
657                 spin_lock_bh(root_lock);
658
659                 val = (test_bit(__QDISC_STATE_RUNNING, &q->state) ||
660                        test_bit(__QDISC_STATE_SCHED, &q->state));
661
662                 spin_unlock_bh(root_lock);
663
664                 if (val)
665                         return true;
666         }
667         return false;
668 }
669
670 void dev_deactivate(struct net_device *dev)
671 {
672         netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
673         dev_deactivate_queue(dev, &dev->rx_queue, &noop_qdisc);
674
675         dev_watchdog_down(dev);
676
677         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
678         synchronize_rcu();
679
680         /* Wait for outstanding qdisc_run calls. */
681         while (some_qdisc_is_busy(dev))
682                 yield();
683 }
684
685 static void dev_init_scheduler_queue(struct net_device *dev,
686                                      struct netdev_queue *dev_queue,
687                                      void *_qdisc)
688 {
689         struct Qdisc *qdisc = _qdisc;
690
691         dev_queue->qdisc = qdisc;
692         dev_queue->qdisc_sleeping = qdisc;
693 }
694
695 void dev_init_scheduler(struct net_device *dev)
696 {
697         netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
698         dev_init_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
699
700         setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
701 }
702
703 static void shutdown_scheduler_queue(struct net_device *dev,
704                                      struct netdev_queue *dev_queue,
705                                      void *_qdisc_default)
706 {
707         struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
708         struct Qdisc *qdisc_default = _qdisc_default;
709
710         if (qdisc) {
711                 rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
712                 dev_queue->qdisc_sleeping = qdisc_default;
713
714                 qdisc_destroy(qdisc);
715         }
716 }
717
718 void dev_shutdown(struct net_device *dev)
719 {
720         netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
721         shutdown_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
722         WARN_ON(timer_pending(&dev->watchdog_timer));
723 }