aboutsummaryrefslogtreecommitdiffstats
path: root/net/sched/sch_generic.c
blob: 7aad0121232cb3aa555572524d7609f061718f65 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
/*
 * net/sched/sch_generic.c	Generic packet scheduler routines.
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *              Jamal Hadi Salim, <hadi@cyberus.ca> 990601
 *              - Ingress support
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/rcupdate.h>
#include <linux/list.h>
#include <net/sock.h>
#include <net/pkt_sched.h>

/* Main transmission queue. */

/* Main qdisc structure lock. 

   However, modifications
   to data, participating in scheduling must be additionally
   protected with dev->queue_lock spinlock.

   The idea is the following:
   - enqueue, dequeue are serialized via top level device
     spinlock dev->queue_lock.
   - tree walking is protected by read_lock_bh(qdisc_tree_lock)
     and this lock is used only in process context.
   - updates to tree are made under rtnl semaphore or
     from softirq context (__qdisc_destroy rcu-callback)
     hence this lock needs local bh disabling.

   qdisc_tree_lock must be grabbed BEFORE dev->queue_lock!
 */
DEFINE_RWLOCK(qdisc_tree_lock);

void qdisc_lock_tree(struct net_device *dev)
{
	write_lock_bh(&qdisc_tree_lock);
	spin_lock_bh(&dev->queue_lock);
}

void qdisc_unlock_tree(struct net_device *dev)
{
	spin_unlock_bh(&dev->queue_lock);
	write_unlock_bh(&qdisc_tree_lock);
}

/* 
   dev->queue_lock serializes queue accesses for this device
   AND dev->qdisc pointer itself.

   netif_tx_lock serializes accesses to device driver.

   dev->queue_lock and netif_tx_lock are mutually exclusive,
   if one is grabbed, another must be free.
 */


/* Kick device.
   Note, that this procedure can be called by a watchdog timer, so that
   we do not check dev->tbusy flag here.

   Returns:  0  - queue is empty.
            >0  - queue is not empty, but throttled.
	    <0  - queue is not empty. Device is throttled, if dev->tbusy != 0.

   NOTE: Called under dev->queue_lock with locally disabled BH.
*/

static inline int qdisc_restart(struct net_device *dev)
{
	struct Qdisc *q = dev->qdisc;
	struct sk_buff *skb;

	/* Dequeue packet */
	if ((skb = q->dequeue(q)) != NULL) {
		unsigned nolock = (dev->features & NETIF_F_LLTX);
		/*
		 * When the driver has LLTX set it does its own locking
		 * in start_xmit. No need to add additional overhead by
		 * locking again. These checks are worth it because
		 * even uncongested locks can be quite expensive.
		 * The driver can do trylock like here too, in case
		 * of lock congestion it should return -1 and the packet
		 * will be requeued.
		 */
		if (!nolock) {
			if (!netif_tx_trylock(dev)) {
			collision:
				/* So, someone grabbed the driver. */
				
				/* It may be transient configuration error,
				   when hard_start_xmit() recurses. We detect
				   it by checking xmit owner and drop the
				   packet when deadloop is detected.
				*/
				if (dev->xmit_lock_owner == smp_processor_id()) {
					kfree_skb(skb);
					if (net_ratelimit())
						printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name);
					return -1;
				}
				__get_cpu_var(netdev_rx_stat).cpu_collision++;
				goto requeue;
			}
		}
		
		{
			/* And release queue */
			spin_unlock(&dev->queue_lock);

			if (!netif_queue_stopped(dev)) {
				int ret;
				if (netdev_nit)
					dev_queue_xmit_nit(skb, dev);

				ret = dev->hard_start_xmit(skb, dev);
				if (ret == NETDEV_TX_OK) { 
					if (!nolock) {
						netif_tx_unlock(dev);
					}
					spin_lock(&dev->queue_lock);
					return -1;
				}
				if (ret == NETDEV_TX_LOCKED && nolock) {
					spin_lock(&dev->queue_lock);
					goto collision; 
				}
			}

			/* NETDEV_TX_BUSY - we need to requeue */
			/* Release the driver */
			if (!nolock) { 
				netif_tx_unlock(dev);
			} 
			spin_lock(&dev->queue_lock);
			q = dev->qdisc;
		}

		/* Device kicked us out :(
		   This is possible in three cases:

		   0. driver is locked
		   1. fastroute is enabled
		   2. device cannot determine busy state
		      before start of transmission (f.e. dialout)
		   3. device is buggy (ppp)
		 */

requeue:
		q->ops->requeue(skb, q);
		netif_schedule(dev);
		return 1;
	}
	BUG_ON((int) q->q.qlen < 0);
	return q->q.qlen;
}

void __qdisc_run(struct net_device *dev)
{
	if (unlikely(dev->qdisc == &noop_qdisc))
		goto out;

	while (qdisc_restart(dev) < 0 && !netif_queue_stopped(dev))
		/* NOTHING */;

out:
	clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
}

static void dev_watchdog(unsigned long arg)
{
	struct net_device *dev = (struct net_device *)arg;

	netif_tx_lock(dev);
	if (dev->qdisc != &noop_qdisc) {
		if (netif_device_present(dev) &&
		    netif_running(dev) &&
		    netif_carrier_ok(dev)) {
			if (netif_queue_stopped(dev) &&
			    time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {

				printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
				       dev->name);
				dev->tx_timeout(dev);
			}
			if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
				dev_hold(dev);
		}
	}
	netif_tx_unlock(dev);

	dev_put(dev);
}

static void dev_watchdog_init(struct net_device *dev)
{
	init_timer(&dev->watchdog_timer);
	dev->watchdog_timer.data = (unsigned long)dev;
	dev->watchdog_timer.function = dev_watchdog;
}

void __netdev_watchdog_up(struct net_device *dev)
{
	if (dev->tx_timeout) {
		if (dev->watchdog_timeo <= 0)
			dev->watchdog_timeo = 5*HZ;
		if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
			dev_hold(dev);
	}
}

static void dev_watchdog_up(struct net_device *dev)
{
	netif_tx_lock_bh(dev);
	__netdev_watchdog_up(dev);
	netif_tx_unlock_bh(dev);
}

static void dev_watchdog_down(struct net_device *dev)
{
	netif_tx_lock_bh(dev);
	if (del_timer(&dev->watchdog_timer))
		dev_put(dev);
	netif_tx_unlock_bh(dev);
}

void netif_carrier_on(struct net_device *dev)
{
	if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state))
		linkwatch_fire_event(dev);
	if (netif_running(dev))
		__netdev_watchdog_up(dev);
}

void netif_carrier_off(struct net_device *dev)
{
	if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
		linkwatch_fire_event(dev);
}

/* "NOOP" scheduler: the best scheduler, recommended for all interfaces
   under all circumstances. It is difficult to invent anything faster or
   cheaper.
 */

static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
{
	kfree_skb(skb);
	return NET_XMIT_CN;
}

static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
{
	return NULL;
}

static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
{
	if (net_ratelimit())
		printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
		       skb->dev->name);
	kfree_skb(skb);
	return NET_XMIT_CN;
}

struct Qdisc_ops noop_qdisc_ops = {
	.id		=	"noop",
	.priv_size	=	0,
	.enqueue	=	noop_enqueue,
	.dequeue	=	noop_dequeue,
	.requeue	=	noop_requeue,
	.owner		=	THIS_MODULE,
};

struct Qdisc noop_qdisc = {
	.enqueue	=	noop_enqueue,
	.dequeue	=	noop_dequeue,
	.flags		=	TCQ_F_BUILTIN,
	.ops		=	&noop_qdisc_ops,	
	.list		=	LIST_HEAD_INIT(noop_qdisc.list),
};

static struct Qdisc_ops noqueue_qdisc_ops = {
	.id		=	"noqueue",
	.priv_size	=	0,
	.enqueue	=	noop_enqueue,
	.dequeue	=	noop_dequeue,
	.requeue	=	noop_requeue,
	.owner		=	THIS_MODULE,
};

static struct Qdisc noqueue_qdisc = {
	.enqueue	=	NULL,
	.dequeue	=	noop_dequeue,
	.flags		=	TCQ_F_BUILTIN,
	.ops		=	&noqueue_qdisc_ops,
	.list		=	LIST_HEAD_INIT(noqueue_qdisc.list),
};


static const u8 prio2band[TC_PRIO_MAX+1] =
	{ 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };

/* 3-band FIFO queue: old style, but should be a bit faster than
   generic prio+fifo combination.
 */

#define PFIFO_FAST_BANDS 3

static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
					     struct Qdisc *qdisc)
{
	struct sk_buff_head *list = qdisc_priv(qdisc);
	return list + prio2band[skb->priority & TC_PRIO_MAX];
}

static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
{
	struct sk_buff_head *list = prio2list(skb, qdisc);

	if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
		qdisc->q.qlen++;
		return __qdisc_enqueue_tail(skb, qdisc, list);
	}

	return qdisc_drop(skb, qdisc);
}

static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
{
	int prio;
	struct sk_buff_head *list = qdisc_priv(qdisc);

	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
		if (!skb_queue_empty(list + prio)) {
			qdisc->q.qlen--;
			return __qdisc_dequeue_head(qdisc, list + prio);
		}
	}

	return NULL;
}

static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
{
	qdisc->q.qlen++;
	return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
}

static void pfifo_fast_reset(struct Qdisc* qdisc)
{
	int prio;
	struct sk_buff_head *list = qdisc_priv(qdisc);

	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
		__qdisc_reset_queue(qdisc, list + prio);

	qdisc->qstats.backlog = 0;
	qdisc->q.qlen = 0;
}

static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
{
	struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };

	memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
	RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
	return skb->len;

rtattr_failure:
	return -1;
}

static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
{
	int prio;
	struct sk_buff_head *list = qdisc_priv(qdisc);

	for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
		skb_queue_head_init(list + prio);

	return 0;
}

static struct Qdisc_ops pfifo_fast_ops = {
	.id		=	"pfifo_fast",
	.priv_size	=	PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
	.enqueue	=	pfifo_fast_enqueue,
	.dequeue	=	pfifo_fast_dequeue,
	.requeue	=	pfifo_fast_requeue,
	.init		=	pfifo_fast_init,
	.reset		=	pfifo_fast_reset,
	.dump		=	pfifo_fast_dump,
	.owner		=	THIS_MODULE,
};

struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops)
{
	void *p;
	struct Qdisc *sch;
	unsigned int size;
	int err = -ENOBUFS;

	/* ensure that the Qdisc and the private data are 32-byte aligned */
	size = QDISC_ALIGN(sizeof(*sch));
	size += ops->priv_size + (QDISC_ALIGNTO - 1);

	p = kmalloc(size, GFP_KERNEL);
	if (!p)
		goto errout;
	memset(p, 0, size);
	sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
	sch->padded = (char *) sch - (char *) p;

	INIT_LIST_HEAD(&sch->list);
	skb_queue_head_init(&sch->q);
	sch->ops = ops;
	sch->enqueue = ops->enqueue;
	sch->dequeue = ops->dequeue;
	sch->dev = dev;
	dev_hold(dev);
	sch->stats_lock = &dev->queue_lock;
	atomic_set(&sch->refcnt, 1);

	return sch;
errout:
	return ERR_PTR(-err);
}

struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops)
{
	struct Qdisc *sch;
	
	sch = qdisc_alloc(dev, ops);
	if (IS_ERR(sch))
		goto errout;

	if (!ops->init || ops->init(sch, NULL) == 0)
		return sch;

	qdisc_destroy(sch);
errout:
	return NULL;
}

/* Under dev->queue_lock and BH! */

void qdisc_reset(struct Qdisc *qdisc)
{
	struct Qdisc_ops *ops = qdisc->ops;

	if (ops->reset)
		ops->reset(qdisc);
}

/* this is the rcu callback function to clean up a qdisc when there 
 * are no further references to it */

static void __qdisc_destroy(struct rcu_head *head)
{
	struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
	struct Qdisc_ops  *ops = qdisc->ops;

#ifdef CONFIG_NET_ESTIMATOR
	gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
#endif
	write_lock(&qdisc_tree_lock);
	if (ops->reset)
		ops->reset(qdisc);
	if (ops->destroy)
		ops->destroy(qdisc);
	write_unlock(&qdisc_tree_lock);
	module_put(ops->owner);

	dev_put(qdisc->dev);
	kfree((char *) qdisc - qdisc->padded);
}

/* Under dev->queue_lock and BH! */

void qdisc_destroy(struct Qdisc *qdisc)
{
	struct list_head cql = LIST_HEAD_INIT(cql);
	struct Qdisc *cq, *q, *n;

	if (qdisc->flags & TCQ_F_BUILTIN ||
		!atomic_dec_and_test(&qdisc->refcnt))
		return;

	if (!list_empty(&qdisc->list)) {
		if (qdisc->ops->cl_ops == NULL)
			list_del(&qdisc->list);
		else
			list_move(&qdisc->list, &cql);
	}

	/* unlink inner qdiscs from dev->qdisc_list immediately */
	list_for_each_entry(cq, &cql, list)
		list_for_each_entry_safe(q, n, &qdisc->dev->qdisc_list, list)
			if (TC_H_MAJ(q->parent) == TC_H_MAJ(cq->handle)) {
				if (q->ops->cl_ops == NULL)
					list_del_init(&q->list);
				else
					list_move_tail(&q->list, &cql);
			}
	list_for_each_entry_safe(cq, n, &cql, list)
		list_del_init(&cq->list);

	call_rcu(&qdisc->q_rcu, __qdisc_destroy);
}

void dev_activate(struct net_device *dev)
{
	/* No queueing discipline is attached to device;
	   create default one i.e. pfifo_fast for devices,
	   which need queueing and noqueue_qdisc for
	   virtual interfaces
	 */

	if (dev->qdisc_sleeping == &noop_qdisc) {
		struct Qdisc *qdisc;
		if (dev->tx_queue_len) {
			qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops);
			if (qdisc == NULL) {
				printk(KERN_INFO "%s: activation failed\n", dev->name);
				return;
			}
			write_lock_bh(&qdisc_tree_lock);
			list_add_tail(&qdisc->list, &dev->qdisc_list);
			write_unlock_bh(&qdisc_tree_lock);
		} else {
			qdisc =  &noqueue_qdisc;
		}
		write_lock_bh(&qdisc_tree_lock);
		dev->qdisc_sleeping = qdisc;
		write_unlock_bh(&qdisc_tree_lock);
	}

	if (!netif_carrier_ok(dev))
		/* Delay activation until next carrier-on event */
		return;

	spin_lock_bh(&dev->queue_lock);
	rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
	if (dev->qdisc != &noqueue_qdisc) {
		dev->trans_start = jiffies;
		dev_watchdog_up(dev);
	}
	spin_unlock_bh(&dev->queue_lock);
}

void dev_deactivate(struct net_device *dev)
{
	struct Qdisc *qdisc;

	spin_lock_bh(&dev->queue_lock);
	qdisc = dev->qdisc;
	dev->qdisc = &noop_qdisc;

	qdisc_reset(qdisc);

	spin_unlock_bh(&dev->queue_lock);

	dev_watchdog_down(dev);

	/* Wait for outstanding dev_queue_xmit calls. */
	synchronize_rcu();

	/* Wait for outstanding qdisc_run calls. */
	while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
		yield();
}

void dev_init_scheduler(struct net_device *dev)
{
	qdisc_lock_tree(dev);
	dev->qdisc = &noop_qdisc;
	dev->qdisc_sleeping = &noop_qdisc;
	INIT_LIST_HEAD(&dev->qdisc_list);
	qdisc_unlock_tree(dev);

	dev_watchdog_init(dev);
}

void dev_shutdown(struct net_device *dev)
{
	struct Qdisc *qdisc;

	qdisc_lock_tree(dev);
	qdisc = dev->qdisc_sleeping;
	dev->qdisc = &noop_qdisc;
	dev->qdisc_sleeping = &noop_qdisc;
	qdisc_destroy(qdisc);
#if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
        if ((qdisc = dev->qdisc_ingress) != NULL) {
		dev->qdisc_ingress = NULL;
		qdisc_destroy(qdisc);
        }
#endif
	BUG_TRAP(!timer_pending(&dev->watchdog_timer));
	qdisc_unlock_tree(dev);
}

EXPORT_SYMBOL(__netdev_watchdog_up);
EXPORT_SYMBOL(netif_carrier_on);
EXPORT_SYMBOL(netif_carrier_off);
EXPORT_SYMBOL(noop_qdisc);
EXPORT_SYMBOL(noop_qdisc_ops);
EXPORT_SYMBOL(qdisc_create_dflt);
EXPORT_SYMBOL(qdisc_alloc);
EXPORT_SYMBOL(qdisc_destroy);
EXPORT_SYMBOL(qdisc_reset);
EXPORT_SYMBOL(qdisc_lock_tree);
EXPORT_SYMBOL(qdisc_unlock_tree);