xref: /openbmc/linux/net/sched/sch_generic.c (revision b6dcefde)
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 dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
41 {
42 	q->gso_skb = skb;
43 	q->qstats.requeues++;
44 	q->q.qlen++;	/* it's still part of the queue */
45 	__netif_schedule(q);
46 
47 	return 0;
48 }
49 
50 static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
51 {
52 	struct sk_buff *skb = q->gso_skb;
53 
54 	if (unlikely(skb)) {
55 		struct net_device *dev = qdisc_dev(q);
56 		struct netdev_queue *txq;
57 
58 		/* check the reason of requeuing without tx lock first */
59 		txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
60 		if (!netif_tx_queue_stopped(txq) &&
61 		    !netif_tx_queue_frozen(txq)) {
62 			q->gso_skb = NULL;
63 			q->q.qlen--;
64 		} else
65 			skb = NULL;
66 	} else {
67 		skb = q->dequeue(q);
68 	}
69 
70 	return skb;
71 }
72 
73 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
74 					   struct netdev_queue *dev_queue,
75 					   struct Qdisc *q)
76 {
77 	int ret;
78 
79 	if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
80 		/*
81 		 * Same CPU holding the lock. It may be a transient
82 		 * configuration error, when hard_start_xmit() recurses. We
83 		 * detect it by checking xmit owner and drop the packet when
84 		 * deadloop is detected. Return OK to try the next skb.
85 		 */
86 		kfree_skb(skb);
87 		if (net_ratelimit())
88 			printk(KERN_WARNING "Dead loop on netdevice %s, "
89 			       "fix it urgently!\n", dev_queue->dev->name);
90 		ret = qdisc_qlen(q);
91 	} else {
92 		/*
93 		 * Another cpu is holding lock, requeue & delay xmits for
94 		 * some time.
95 		 */
96 		__get_cpu_var(netdev_rx_stat).cpu_collision++;
97 		ret = dev_requeue_skb(skb, q);
98 	}
99 
100 	return ret;
101 }
102 
103 /*
104  * Transmit one skb, and handle the return status as required. Holding the
105  * __QDISC_STATE_RUNNING bit guarantees that only one CPU can execute this
106  * function.
107  *
108  * Returns to the caller:
109  *				0  - queue is empty or throttled.
110  *				>0 - queue is not empty.
111  */
112 int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
113 		    struct net_device *dev, struct netdev_queue *txq,
114 		    spinlock_t *root_lock)
115 {
116 	int ret = NETDEV_TX_BUSY;
117 
118 	/* And release qdisc */
119 	spin_unlock(root_lock);
120 
121 	HARD_TX_LOCK(dev, txq, smp_processor_id());
122 	if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
123 		ret = dev_hard_start_xmit(skb, dev, txq);
124 
125 	HARD_TX_UNLOCK(dev, txq);
126 
127 	spin_lock(root_lock);
128 
129 	if (dev_xmit_complete(ret)) {
130 		/* Driver sent out skb successfully or skb was consumed */
131 		ret = qdisc_qlen(q);
132 	} else if (ret == NETDEV_TX_LOCKED) {
133 		/* Driver try lock failed */
134 		ret = handle_dev_cpu_collision(skb, txq, q);
135 	} else {
136 		/* Driver returned NETDEV_TX_BUSY - requeue skb */
137 		if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
138 			printk(KERN_WARNING "BUG %s code %d qlen %d\n",
139 			       dev->name, ret, q->q.qlen);
140 
141 		ret = dev_requeue_skb(skb, q);
142 	}
143 
144 	if (ret && (netif_tx_queue_stopped(txq) ||
145 		    netif_tx_queue_frozen(txq)))
146 		ret = 0;
147 
148 	return ret;
149 }
150 
151 /*
152  * NOTE: Called under qdisc_lock(q) with locally disabled BH.
153  *
154  * __QDISC_STATE_RUNNING guarantees only one CPU can process
155  * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
156  * this queue.
157  *
158  *  netif_tx_lock serializes accesses to device driver.
159  *
160  *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
161  *  if one is grabbed, another must be free.
162  *
163  * Note, that this procedure can be called by a watchdog timer
164  *
165  * Returns to the caller:
166  *				0  - queue is empty or throttled.
167  *				>0 - queue is not empty.
168  *
169  */
170 static inline int qdisc_restart(struct Qdisc *q)
171 {
172 	struct netdev_queue *txq;
173 	struct net_device *dev;
174 	spinlock_t *root_lock;
175 	struct sk_buff *skb;
176 
177 	/* Dequeue packet */
178 	skb = dequeue_skb(q);
179 	if (unlikely(!skb))
180 		return 0;
181 
182 	root_lock = qdisc_lock(q);
183 	dev = qdisc_dev(q);
184 	txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
185 
186 	return sch_direct_xmit(skb, q, dev, txq, root_lock);
187 }
188 
189 void __qdisc_run(struct Qdisc *q)
190 {
191 	unsigned long start_time = jiffies;
192 
193 	while (qdisc_restart(q)) {
194 		/*
195 		 * Postpone processing if
196 		 * 1. another process needs the CPU;
197 		 * 2. we've been doing it for too long.
198 		 */
199 		if (need_resched() || jiffies != start_time) {
200 			__netif_schedule(q);
201 			break;
202 		}
203 	}
204 
205 	clear_bit(__QDISC_STATE_RUNNING, &q->state);
206 }
207 
208 unsigned long dev_trans_start(struct net_device *dev)
209 {
210 	unsigned long val, res = dev->trans_start;
211 	unsigned int i;
212 
213 	for (i = 0; i < dev->num_tx_queues; i++) {
214 		val = netdev_get_tx_queue(dev, i)->trans_start;
215 		if (val && time_after(val, res))
216 			res = val;
217 	}
218 	dev->trans_start = res;
219 	return res;
220 }
221 EXPORT_SYMBOL(dev_trans_start);
222 
223 static void dev_watchdog(unsigned long arg)
224 {
225 	struct net_device *dev = (struct net_device *)arg;
226 
227 	netif_tx_lock(dev);
228 	if (!qdisc_tx_is_noop(dev)) {
229 		if (netif_device_present(dev) &&
230 		    netif_running(dev) &&
231 		    netif_carrier_ok(dev)) {
232 			int some_queue_timedout = 0;
233 			unsigned int i;
234 			unsigned long trans_start;
235 
236 			for (i = 0; i < dev->num_tx_queues; i++) {
237 				struct netdev_queue *txq;
238 
239 				txq = netdev_get_tx_queue(dev, i);
240 				/*
241 				 * old device drivers set dev->trans_start
242 				 */
243 				trans_start = txq->trans_start ? : dev->trans_start;
244 				if (netif_tx_queue_stopped(txq) &&
245 				    time_after(jiffies, (trans_start +
246 							 dev->watchdog_timeo))) {
247 					some_queue_timedout = 1;
248 					break;
249 				}
250 			}
251 
252 			if (some_queue_timedout) {
253 				char drivername[64];
254 				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
255 				       dev->name, netdev_drivername(dev, drivername, 64), i);
256 				dev->netdev_ops->ndo_tx_timeout(dev);
257 			}
258 			if (!mod_timer(&dev->watchdog_timer,
259 				       round_jiffies(jiffies +
260 						     dev->watchdog_timeo)))
261 				dev_hold(dev);
262 		}
263 	}
264 	netif_tx_unlock(dev);
265 
266 	dev_put(dev);
267 }
268 
269 void __netdev_watchdog_up(struct net_device *dev)
270 {
271 	if (dev->netdev_ops->ndo_tx_timeout) {
272 		if (dev->watchdog_timeo <= 0)
273 			dev->watchdog_timeo = 5*HZ;
274 		if (!mod_timer(&dev->watchdog_timer,
275 			       round_jiffies(jiffies + dev->watchdog_timeo)))
276 			dev_hold(dev);
277 	}
278 }
279 
280 static void dev_watchdog_up(struct net_device *dev)
281 {
282 	__netdev_watchdog_up(dev);
283 }
284 
285 static void dev_watchdog_down(struct net_device *dev)
286 {
287 	netif_tx_lock_bh(dev);
288 	if (del_timer(&dev->watchdog_timer))
289 		dev_put(dev);
290 	netif_tx_unlock_bh(dev);
291 }
292 
293 /**
294  *	netif_carrier_on - set carrier
295  *	@dev: network device
296  *
297  * Device has detected that carrier.
298  */
299 void netif_carrier_on(struct net_device *dev)
300 {
301 	if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
302 		if (dev->reg_state == NETREG_UNINITIALIZED)
303 			return;
304 		linkwatch_fire_event(dev);
305 		if (netif_running(dev))
306 			__netdev_watchdog_up(dev);
307 	}
308 }
309 EXPORT_SYMBOL(netif_carrier_on);
310 
311 /**
312  *	netif_carrier_off - clear carrier
313  *	@dev: network device
314  *
315  * Device has detected loss of carrier.
316  */
317 void netif_carrier_off(struct net_device *dev)
318 {
319 	if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
320 		if (dev->reg_state == NETREG_UNINITIALIZED)
321 			return;
322 		linkwatch_fire_event(dev);
323 	}
324 }
325 EXPORT_SYMBOL(netif_carrier_off);
326 
327 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
328    under all circumstances. It is difficult to invent anything faster or
329    cheaper.
330  */
331 
332 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
333 {
334 	kfree_skb(skb);
335 	return NET_XMIT_CN;
336 }
337 
338 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
339 {
340 	return NULL;
341 }
342 
343 struct Qdisc_ops noop_qdisc_ops __read_mostly = {
344 	.id		=	"noop",
345 	.priv_size	=	0,
346 	.enqueue	=	noop_enqueue,
347 	.dequeue	=	noop_dequeue,
348 	.peek		=	noop_dequeue,
349 	.owner		=	THIS_MODULE,
350 };
351 
352 static struct netdev_queue noop_netdev_queue = {
353 	.qdisc		=	&noop_qdisc,
354 	.qdisc_sleeping	=	&noop_qdisc,
355 };
356 
357 struct Qdisc noop_qdisc = {
358 	.enqueue	=	noop_enqueue,
359 	.dequeue	=	noop_dequeue,
360 	.flags		=	TCQ_F_BUILTIN,
361 	.ops		=	&noop_qdisc_ops,
362 	.list		=	LIST_HEAD_INIT(noop_qdisc.list),
363 	.q.lock		=	__SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
364 	.dev_queue	=	&noop_netdev_queue,
365 };
366 EXPORT_SYMBOL(noop_qdisc);
367 
368 static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
369 	.id		=	"noqueue",
370 	.priv_size	=	0,
371 	.enqueue	=	noop_enqueue,
372 	.dequeue	=	noop_dequeue,
373 	.peek		=	noop_dequeue,
374 	.owner		=	THIS_MODULE,
375 };
376 
377 static struct Qdisc noqueue_qdisc;
378 static struct netdev_queue noqueue_netdev_queue = {
379 	.qdisc		=	&noqueue_qdisc,
380 	.qdisc_sleeping	=	&noqueue_qdisc,
381 };
382 
383 static struct Qdisc noqueue_qdisc = {
384 	.enqueue	=	NULL,
385 	.dequeue	=	noop_dequeue,
386 	.flags		=	TCQ_F_BUILTIN,
387 	.ops		=	&noqueue_qdisc_ops,
388 	.list		=	LIST_HEAD_INIT(noqueue_qdisc.list),
389 	.q.lock		=	__SPIN_LOCK_UNLOCKED(noqueue_qdisc.q.lock),
390 	.dev_queue	=	&noqueue_netdev_queue,
391 };
392 
393 
394 static const u8 prio2band[TC_PRIO_MAX+1] =
395 	{ 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
396 
397 /* 3-band FIFO queue: old style, but should be a bit faster than
398    generic prio+fifo combination.
399  */
400 
401 #define PFIFO_FAST_BANDS 3
402 
403 /*
404  * Private data for a pfifo_fast scheduler containing:
405  * 	- queues for the three band
406  * 	- bitmap indicating which of the bands contain skbs
407  */
408 struct pfifo_fast_priv {
409 	u32 bitmap;
410 	struct sk_buff_head q[PFIFO_FAST_BANDS];
411 };
412 
413 /*
414  * Convert a bitmap to the first band number where an skb is queued, where:
415  * 	bitmap=0 means there are no skbs on any band.
416  * 	bitmap=1 means there is an skb on band 0.
417  *	bitmap=7 means there are skbs on all 3 bands, etc.
418  */
419 static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0};
420 
421 static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv,
422 					     int band)
423 {
424 	return priv->q + band;
425 }
426 
427 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
428 {
429 	if (skb_queue_len(&qdisc->q) < qdisc_dev(qdisc)->tx_queue_len) {
430 		int band = prio2band[skb->priority & TC_PRIO_MAX];
431 		struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
432 		struct sk_buff_head *list = band2list(priv, band);
433 
434 		priv->bitmap |= (1 << band);
435 		qdisc->q.qlen++;
436 		return __qdisc_enqueue_tail(skb, qdisc, list);
437 	}
438 
439 	return qdisc_drop(skb, qdisc);
440 }
441 
442 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
443 {
444 	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
445 	int band = bitmap2band[priv->bitmap];
446 
447 	if (likely(band >= 0)) {
448 		struct sk_buff_head *list = band2list(priv, band);
449 		struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list);
450 
451 		qdisc->q.qlen--;
452 		if (skb_queue_empty(list))
453 			priv->bitmap &= ~(1 << band);
454 
455 		return skb;
456 	}
457 
458 	return NULL;
459 }
460 
461 static struct sk_buff *pfifo_fast_peek(struct Qdisc* qdisc)
462 {
463 	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
464 	int band = bitmap2band[priv->bitmap];
465 
466 	if (band >= 0) {
467 		struct sk_buff_head *list = band2list(priv, band);
468 
469 		return skb_peek(list);
470 	}
471 
472 	return NULL;
473 }
474 
475 static void pfifo_fast_reset(struct Qdisc* qdisc)
476 {
477 	int prio;
478 	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
479 
480 	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
481 		__qdisc_reset_queue(qdisc, band2list(priv, prio));
482 
483 	priv->bitmap = 0;
484 	qdisc->qstats.backlog = 0;
485 	qdisc->q.qlen = 0;
486 }
487 
488 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
489 {
490 	struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
491 
492 	memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
493 	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
494 	return skb->len;
495 
496 nla_put_failure:
497 	return -1;
498 }
499 
500 static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
501 {
502 	int prio;
503 	struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
504 
505 	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
506 		skb_queue_head_init(band2list(priv, prio));
507 
508 	return 0;
509 }
510 
511 struct Qdisc_ops pfifo_fast_ops __read_mostly = {
512 	.id		=	"pfifo_fast",
513 	.priv_size	=	sizeof(struct pfifo_fast_priv),
514 	.enqueue	=	pfifo_fast_enqueue,
515 	.dequeue	=	pfifo_fast_dequeue,
516 	.peek		=	pfifo_fast_peek,
517 	.init		=	pfifo_fast_init,
518 	.reset		=	pfifo_fast_reset,
519 	.dump		=	pfifo_fast_dump,
520 	.owner		=	THIS_MODULE,
521 };
522 
523 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
524 			  struct Qdisc_ops *ops)
525 {
526 	void *p;
527 	struct Qdisc *sch;
528 	unsigned int size;
529 	int err = -ENOBUFS;
530 
531 	/* ensure that the Qdisc and the private data are 32-byte aligned */
532 	size = QDISC_ALIGN(sizeof(*sch));
533 	size += ops->priv_size + (QDISC_ALIGNTO - 1);
534 
535 	p = kzalloc(size, GFP_KERNEL);
536 	if (!p)
537 		goto errout;
538 	sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
539 	sch->padded = (char *) sch - (char *) p;
540 
541 	INIT_LIST_HEAD(&sch->list);
542 	skb_queue_head_init(&sch->q);
543 	sch->ops = ops;
544 	sch->enqueue = ops->enqueue;
545 	sch->dequeue = ops->dequeue;
546 	sch->dev_queue = dev_queue;
547 	dev_hold(qdisc_dev(sch));
548 	atomic_set(&sch->refcnt, 1);
549 
550 	return sch;
551 errout:
552 	return ERR_PTR(err);
553 }
554 
555 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
556 				 struct netdev_queue *dev_queue,
557 				 struct Qdisc_ops *ops,
558 				 unsigned int parentid)
559 {
560 	struct Qdisc *sch;
561 
562 	sch = qdisc_alloc(dev_queue, ops);
563 	if (IS_ERR(sch))
564 		goto errout;
565 	sch->parent = parentid;
566 
567 	if (!ops->init || ops->init(sch, NULL) == 0)
568 		return sch;
569 
570 	qdisc_destroy(sch);
571 errout:
572 	return NULL;
573 }
574 EXPORT_SYMBOL(qdisc_create_dflt);
575 
576 /* Under qdisc_lock(qdisc) and BH! */
577 
578 void qdisc_reset(struct Qdisc *qdisc)
579 {
580 	const struct Qdisc_ops *ops = qdisc->ops;
581 
582 	if (ops->reset)
583 		ops->reset(qdisc);
584 
585 	if (qdisc->gso_skb) {
586 		kfree_skb(qdisc->gso_skb);
587 		qdisc->gso_skb = NULL;
588 		qdisc->q.qlen = 0;
589 	}
590 }
591 EXPORT_SYMBOL(qdisc_reset);
592 
593 void qdisc_destroy(struct Qdisc *qdisc)
594 {
595 	const struct Qdisc_ops  *ops = qdisc->ops;
596 
597 	if (qdisc->flags & TCQ_F_BUILTIN ||
598 	    !atomic_dec_and_test(&qdisc->refcnt))
599 		return;
600 
601 #ifdef CONFIG_NET_SCHED
602 	qdisc_list_del(qdisc);
603 
604 	qdisc_put_stab(qdisc->stab);
605 #endif
606 	gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
607 	if (ops->reset)
608 		ops->reset(qdisc);
609 	if (ops->destroy)
610 		ops->destroy(qdisc);
611 
612 	module_put(ops->owner);
613 	dev_put(qdisc_dev(qdisc));
614 
615 	kfree_skb(qdisc->gso_skb);
616 	kfree((char *) qdisc - qdisc->padded);
617 }
618 EXPORT_SYMBOL(qdisc_destroy);
619 
620 /* Attach toplevel qdisc to device queue. */
621 struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
622 			      struct Qdisc *qdisc)
623 {
624 	struct Qdisc *oqdisc = dev_queue->qdisc_sleeping;
625 	spinlock_t *root_lock;
626 
627 	root_lock = qdisc_lock(oqdisc);
628 	spin_lock_bh(root_lock);
629 
630 	/* Prune old scheduler */
631 	if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
632 		qdisc_reset(oqdisc);
633 
634 	/* ... and graft new one */
635 	if (qdisc == NULL)
636 		qdisc = &noop_qdisc;
637 	dev_queue->qdisc_sleeping = qdisc;
638 	rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc);
639 
640 	spin_unlock_bh(root_lock);
641 
642 	return oqdisc;
643 }
644 
645 static void attach_one_default_qdisc(struct net_device *dev,
646 				     struct netdev_queue *dev_queue,
647 				     void *_unused)
648 {
649 	struct Qdisc *qdisc;
650 
651 	if (dev->tx_queue_len) {
652 		qdisc = qdisc_create_dflt(dev, dev_queue,
653 					  &pfifo_fast_ops, TC_H_ROOT);
654 		if (!qdisc) {
655 			printk(KERN_INFO "%s: activation failed\n", dev->name);
656 			return;
657 		}
658 
659 		/* Can by-pass the queue discipline for default qdisc */
660 		qdisc->flags |= TCQ_F_CAN_BYPASS;
661 	} else {
662 		qdisc =  &noqueue_qdisc;
663 	}
664 	dev_queue->qdisc_sleeping = qdisc;
665 }
666 
667 static void attach_default_qdiscs(struct net_device *dev)
668 {
669 	struct netdev_queue *txq;
670 	struct Qdisc *qdisc;
671 
672 	txq = netdev_get_tx_queue(dev, 0);
673 
674 	if (!netif_is_multiqueue(dev) || dev->tx_queue_len == 0) {
675 		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
676 		dev->qdisc = txq->qdisc_sleeping;
677 		atomic_inc(&dev->qdisc->refcnt);
678 	} else {
679 		qdisc = qdisc_create_dflt(dev, txq, &mq_qdisc_ops, TC_H_ROOT);
680 		if (qdisc) {
681 			qdisc->ops->attach(qdisc);
682 			dev->qdisc = qdisc;
683 		}
684 	}
685 }
686 
687 static void transition_one_qdisc(struct net_device *dev,
688 				 struct netdev_queue *dev_queue,
689 				 void *_need_watchdog)
690 {
691 	struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
692 	int *need_watchdog_p = _need_watchdog;
693 
694 	if (!(new_qdisc->flags & TCQ_F_BUILTIN))
695 		clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
696 
697 	rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
698 	if (need_watchdog_p && new_qdisc != &noqueue_qdisc) {
699 		dev_queue->trans_start = 0;
700 		*need_watchdog_p = 1;
701 	}
702 }
703 
704 void dev_activate(struct net_device *dev)
705 {
706 	int need_watchdog;
707 
708 	/* No queueing discipline is attached to device;
709 	   create default one i.e. pfifo_fast for devices,
710 	   which need queueing and noqueue_qdisc for
711 	   virtual interfaces
712 	 */
713 
714 	if (dev->qdisc == &noop_qdisc)
715 		attach_default_qdiscs(dev);
716 
717 	if (!netif_carrier_ok(dev))
718 		/* Delay activation until next carrier-on event */
719 		return;
720 
721 	need_watchdog = 0;
722 	netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
723 	transition_one_qdisc(dev, &dev->rx_queue, NULL);
724 
725 	if (need_watchdog) {
726 		dev->trans_start = jiffies;
727 		dev_watchdog_up(dev);
728 	}
729 }
730 
731 static void dev_deactivate_queue(struct net_device *dev,
732 				 struct netdev_queue *dev_queue,
733 				 void *_qdisc_default)
734 {
735 	struct Qdisc *qdisc_default = _qdisc_default;
736 	struct Qdisc *qdisc;
737 
738 	qdisc = dev_queue->qdisc;
739 	if (qdisc) {
740 		spin_lock_bh(qdisc_lock(qdisc));
741 
742 		if (!(qdisc->flags & TCQ_F_BUILTIN))
743 			set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
744 
745 		rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
746 		qdisc_reset(qdisc);
747 
748 		spin_unlock_bh(qdisc_lock(qdisc));
749 	}
750 }
751 
752 static bool some_qdisc_is_busy(struct net_device *dev)
753 {
754 	unsigned int i;
755 
756 	for (i = 0; i < dev->num_tx_queues; i++) {
757 		struct netdev_queue *dev_queue;
758 		spinlock_t *root_lock;
759 		struct Qdisc *q;
760 		int val;
761 
762 		dev_queue = netdev_get_tx_queue(dev, i);
763 		q = dev_queue->qdisc_sleeping;
764 		root_lock = qdisc_lock(q);
765 
766 		spin_lock_bh(root_lock);
767 
768 		val = (test_bit(__QDISC_STATE_RUNNING, &q->state) ||
769 		       test_bit(__QDISC_STATE_SCHED, &q->state));
770 
771 		spin_unlock_bh(root_lock);
772 
773 		if (val)
774 			return true;
775 	}
776 	return false;
777 }
778 
779 void dev_deactivate(struct net_device *dev)
780 {
781 	netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
782 	dev_deactivate_queue(dev, &dev->rx_queue, &noop_qdisc);
783 
784 	dev_watchdog_down(dev);
785 
786 	/* Wait for outstanding qdisc-less dev_queue_xmit calls. */
787 	synchronize_rcu();
788 
789 	/* Wait for outstanding qdisc_run calls. */
790 	while (some_qdisc_is_busy(dev))
791 		yield();
792 }
793 
794 static void dev_init_scheduler_queue(struct net_device *dev,
795 				     struct netdev_queue *dev_queue,
796 				     void *_qdisc)
797 {
798 	struct Qdisc *qdisc = _qdisc;
799 
800 	dev_queue->qdisc = qdisc;
801 	dev_queue->qdisc_sleeping = qdisc;
802 }
803 
804 void dev_init_scheduler(struct net_device *dev)
805 {
806 	dev->qdisc = &noop_qdisc;
807 	netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
808 	dev_init_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
809 
810 	setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
811 }
812 
813 static void shutdown_scheduler_queue(struct net_device *dev,
814 				     struct netdev_queue *dev_queue,
815 				     void *_qdisc_default)
816 {
817 	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
818 	struct Qdisc *qdisc_default = _qdisc_default;
819 
820 	if (qdisc) {
821 		rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
822 		dev_queue->qdisc_sleeping = qdisc_default;
823 
824 		qdisc_destroy(qdisc);
825 	}
826 }
827 
828 void dev_shutdown(struct net_device *dev)
829 {
830 	netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
831 	shutdown_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
832 	qdisc_destroy(dev->qdisc);
833 	dev->qdisc = &noop_qdisc;
834 
835 	WARN_ON(timer_pending(&dev->watchdog_timer));
836 }
837