netdev: Create netdev_queue abstraction.
[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  * dev->queue_lock spinlock.
33  *
34  * The idea is the following:
35  * - enqueue, dequeue are serialized via top level device
36  *   spinlock dev->queue_lock.
37  * - ingress filtering is serialized via top level device
38  *   spinlock dev->ingress_lock.
39  * - updates to tree and tree walking are only done under the rtnl mutex.
40  */
41
42 void qdisc_lock_tree(struct net_device *dev)
43         __acquires(dev->queue_lock)
44         __acquires(dev->ingress_lock)
45 {
46         spin_lock_bh(&dev->queue_lock);
47         spin_lock(&dev->ingress_lock);
48 }
49 EXPORT_SYMBOL(qdisc_lock_tree);
50
51 void qdisc_unlock_tree(struct net_device *dev)
52         __releases(dev->ingress_lock)
53         __releases(dev->queue_lock)
54 {
55         spin_unlock(&dev->ingress_lock);
56         spin_unlock_bh(&dev->queue_lock);
57 }
58 EXPORT_SYMBOL(qdisc_unlock_tree);
59
60 static inline int qdisc_qlen(struct Qdisc *q)
61 {
62         return q->q.qlen;
63 }
64
65 static inline int dev_requeue_skb(struct sk_buff *skb, struct net_device *dev,
66                                   struct Qdisc *q)
67 {
68         if (unlikely(skb->next))
69                 dev->gso_skb = skb;
70         else
71                 q->ops->requeue(skb, q);
72
73         netif_schedule(dev);
74         return 0;
75 }
76
77 static inline struct sk_buff *dev_dequeue_skb(struct net_device *dev,
78                                               struct Qdisc *q)
79 {
80         struct sk_buff *skb;
81
82         if ((skb = dev->gso_skb))
83                 dev->gso_skb = NULL;
84         else
85                 skb = q->dequeue(q);
86
87         return skb;
88 }
89
90 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
91                                            struct net_device *dev,
92                                            struct Qdisc *q)
93 {
94         int ret;
95
96         if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
97                 /*
98                  * Same CPU holding the lock. It may be a transient
99                  * configuration error, when hard_start_xmit() recurses. We
100                  * detect it by checking xmit owner and drop the packet when
101                  * deadloop is detected. Return OK to try the next skb.
102                  */
103                 kfree_skb(skb);
104                 if (net_ratelimit())
105                         printk(KERN_WARNING "Dead loop on netdevice %s, "
106                                "fix it urgently!\n", dev->name);
107                 ret = qdisc_qlen(q);
108         } else {
109                 /*
110                  * Another cpu is holding lock, requeue & delay xmits for
111                  * some time.
112                  */
113                 __get_cpu_var(netdev_rx_stat).cpu_collision++;
114                 ret = dev_requeue_skb(skb, dev, q);
115         }
116
117         return ret;
118 }
119
120 /*
121  * NOTE: Called under dev->queue_lock with locally disabled BH.
122  *
123  * __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
124  * device at a time. dev->queue_lock serializes queue accesses for
125  * this device AND dev->qdisc pointer itself.
126  *
127  *  netif_tx_lock serializes accesses to device driver.
128  *
129  *  dev->queue_lock and netif_tx_lock are mutually exclusive,
130  *  if one is grabbed, another must be free.
131  *
132  * Note, that this procedure can be called by a watchdog timer
133  *
134  * Returns to the caller:
135  *                              0  - queue is empty or throttled.
136  *                              >0 - queue is not empty.
137  *
138  */
139 static inline int qdisc_restart(struct net_device *dev)
140 {
141         struct Qdisc *q = dev->qdisc;
142         struct sk_buff *skb;
143         int ret = NETDEV_TX_BUSY;
144
145         /* Dequeue packet */
146         if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
147                 return 0;
148
149
150         /* And release queue */
151         spin_unlock(&dev->queue_lock);
152
153         HARD_TX_LOCK(dev, smp_processor_id());
154         if (!netif_subqueue_stopped(dev, skb))
155                 ret = dev_hard_start_xmit(skb, dev);
156         HARD_TX_UNLOCK(dev);
157
158         spin_lock(&dev->queue_lock);
159         q = dev->qdisc;
160
161         switch (ret) {
162         case NETDEV_TX_OK:
163                 /* Driver sent out skb successfully */
164                 ret = qdisc_qlen(q);
165                 break;
166
167         case NETDEV_TX_LOCKED:
168                 /* Driver try lock failed */
169                 ret = handle_dev_cpu_collision(skb, dev, q);
170                 break;
171
172         default:
173                 /* Driver returned NETDEV_TX_BUSY - requeue skb */
174                 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
175                         printk(KERN_WARNING "BUG %s code %d qlen %d\n",
176                                dev->name, ret, q->q.qlen);
177
178                 ret = dev_requeue_skb(skb, dev, q);
179                 break;
180         }
181
182         return ret;
183 }
184
185 void __qdisc_run(struct net_device *dev)
186 {
187         unsigned long start_time = jiffies;
188
189         while (qdisc_restart(dev)) {
190                 if (netif_queue_stopped(dev))
191                         break;
192
193                 /*
194                  * Postpone processing if
195                  * 1. another process needs the CPU;
196                  * 2. we've been doing it for too long.
197                  */
198                 if (need_resched() || jiffies != start_time) {
199                         netif_schedule(dev);
200                         break;
201                 }
202         }
203
204         clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
205 }
206
207 static void dev_watchdog(unsigned long arg)
208 {
209         struct net_device *dev = (struct net_device *)arg;
210
211         netif_tx_lock(dev);
212         if (dev->qdisc != &noop_qdisc) {
213                 if (netif_device_present(dev) &&
214                     netif_running(dev) &&
215                     netif_carrier_ok(dev)) {
216                         if (netif_queue_stopped(dev) &&
217                             time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {
218
219                                 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
220                                        dev->name);
221                                 dev->tx_timeout(dev);
222                                 WARN_ON_ONCE(1);
223                         }
224                         if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + 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 struct Qdisc noop_qdisc = {
321         .enqueue        =       noop_enqueue,
322         .dequeue        =       noop_dequeue,
323         .flags          =       TCQ_F_BUILTIN,
324         .ops            =       &noop_qdisc_ops,
325         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
326 };
327 EXPORT_SYMBOL(noop_qdisc);
328
329 static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
330         .id             =       "noqueue",
331         .priv_size      =       0,
332         .enqueue        =       noop_enqueue,
333         .dequeue        =       noop_dequeue,
334         .requeue        =       noop_requeue,
335         .owner          =       THIS_MODULE,
336 };
337
338 static struct Qdisc noqueue_qdisc = {
339         .enqueue        =       NULL,
340         .dequeue        =       noop_dequeue,
341         .flags          =       TCQ_F_BUILTIN,
342         .ops            =       &noqueue_qdisc_ops,
343         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
344 };
345
346
347 static const u8 prio2band[TC_PRIO_MAX+1] =
348         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
349
350 /* 3-band FIFO queue: old style, but should be a bit faster than
351    generic prio+fifo combination.
352  */
353
354 #define PFIFO_FAST_BANDS 3
355
356 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
357                                              struct Qdisc *qdisc)
358 {
359         struct sk_buff_head *list = qdisc_priv(qdisc);
360         return list + prio2band[skb->priority & TC_PRIO_MAX];
361 }
362
363 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
364 {
365         struct sk_buff_head *list = prio2list(skb, qdisc);
366
367         if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
368                 qdisc->q.qlen++;
369                 return __qdisc_enqueue_tail(skb, qdisc, list);
370         }
371
372         return qdisc_drop(skb, qdisc);
373 }
374
375 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
376 {
377         int prio;
378         struct sk_buff_head *list = qdisc_priv(qdisc);
379
380         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
381                 if (!skb_queue_empty(list + prio)) {
382                         qdisc->q.qlen--;
383                         return __qdisc_dequeue_head(qdisc, list + prio);
384                 }
385         }
386
387         return NULL;
388 }
389
390 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
391 {
392         qdisc->q.qlen++;
393         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
394 }
395
396 static void pfifo_fast_reset(struct Qdisc* qdisc)
397 {
398         int prio;
399         struct sk_buff_head *list = qdisc_priv(qdisc);
400
401         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
402                 __qdisc_reset_queue(qdisc, list + prio);
403
404         qdisc->qstats.backlog = 0;
405         qdisc->q.qlen = 0;
406 }
407
408 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
409 {
410         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
411
412         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
413         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
414         return skb->len;
415
416 nla_put_failure:
417         return -1;
418 }
419
420 static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
421 {
422         int prio;
423         struct sk_buff_head *list = qdisc_priv(qdisc);
424
425         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
426                 skb_queue_head_init(list + prio);
427
428         return 0;
429 }
430
431 static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
432         .id             =       "pfifo_fast",
433         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
434         .enqueue        =       pfifo_fast_enqueue,
435         .dequeue        =       pfifo_fast_dequeue,
436         .requeue        =       pfifo_fast_requeue,
437         .init           =       pfifo_fast_init,
438         .reset          =       pfifo_fast_reset,
439         .dump           =       pfifo_fast_dump,
440         .owner          =       THIS_MODULE,
441 };
442
443 struct Qdisc *qdisc_alloc(struct net_device *dev,
444                           struct netdev_queue *dev_queue,
445                           struct Qdisc_ops *ops)
446 {
447         void *p;
448         struct Qdisc *sch;
449         unsigned int size;
450         int err = -ENOBUFS;
451
452         /* ensure that the Qdisc and the private data are 32-byte aligned */
453         size = QDISC_ALIGN(sizeof(*sch));
454         size += ops->priv_size + (QDISC_ALIGNTO - 1);
455
456         p = kzalloc(size, GFP_KERNEL);
457         if (!p)
458                 goto errout;
459         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
460         sch->padded = (char *) sch - (char *) p;
461
462         INIT_LIST_HEAD(&sch->list);
463         skb_queue_head_init(&sch->q);
464         sch->ops = ops;
465         sch->enqueue = ops->enqueue;
466         sch->dequeue = ops->dequeue;
467         sch->dev_queue = dev_queue;
468         sch->dev = dev;
469         dev_hold(dev);
470         atomic_set(&sch->refcnt, 1);
471
472         return sch;
473 errout:
474         return ERR_PTR(err);
475 }
476
477 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
478                                  struct netdev_queue *dev_queue,
479                                  struct Qdisc_ops *ops,
480                                  unsigned int parentid)
481 {
482         struct Qdisc *sch;
483
484         sch = qdisc_alloc(dev, dev_queue, ops);
485         if (IS_ERR(sch))
486                 goto errout;
487         sch->stats_lock = &dev->queue_lock;
488         sch->parent = parentid;
489
490         if (!ops->init || ops->init(sch, NULL) == 0)
491                 return sch;
492
493         qdisc_destroy(sch);
494 errout:
495         return NULL;
496 }
497 EXPORT_SYMBOL(qdisc_create_dflt);
498
499 /* Under dev->queue_lock and BH! */
500
501 void qdisc_reset(struct Qdisc *qdisc)
502 {
503         const struct Qdisc_ops *ops = qdisc->ops;
504
505         if (ops->reset)
506                 ops->reset(qdisc);
507 }
508 EXPORT_SYMBOL(qdisc_reset);
509
510 /* this is the rcu callback function to clean up a qdisc when there
511  * are no further references to it */
512
513 static void __qdisc_destroy(struct rcu_head *head)
514 {
515         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
516         kfree((char *) qdisc - qdisc->padded);
517 }
518
519 /* Under dev->queue_lock and BH! */
520
521 void qdisc_destroy(struct Qdisc *qdisc)
522 {
523         const struct Qdisc_ops  *ops = qdisc->ops;
524
525         if (qdisc->flags & TCQ_F_BUILTIN ||
526             !atomic_dec_and_test(&qdisc->refcnt))
527                 return;
528
529         list_del(&qdisc->list);
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);
538         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
539 }
540 EXPORT_SYMBOL(qdisc_destroy);
541
542 void dev_activate(struct net_device *dev)
543 {
544         /* No queueing discipline is attached to device;
545            create default one i.e. pfifo_fast for devices,
546            which need queueing and noqueue_qdisc for
547            virtual interfaces
548          */
549
550         if (dev->qdisc_sleeping == &noop_qdisc) {
551                 struct Qdisc *qdisc;
552                 if (dev->tx_queue_len) {
553                         qdisc = qdisc_create_dflt(dev, &dev->tx_queue,
554                                                   &pfifo_fast_ops,
555                                                   TC_H_ROOT);
556                         if (qdisc == NULL) {
557                                 printk(KERN_INFO "%s: activation failed\n", dev->name);
558                                 return;
559                         }
560                         list_add_tail(&qdisc->list, &dev->qdisc_list);
561                 } else {
562                         qdisc =  &noqueue_qdisc;
563                 }
564                 dev->qdisc_sleeping = qdisc;
565         }
566
567         if (!netif_carrier_ok(dev))
568                 /* Delay activation until next carrier-on event */
569                 return;
570
571         spin_lock_bh(&dev->queue_lock);
572         rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
573         if (dev->qdisc != &noqueue_qdisc) {
574                 dev->trans_start = jiffies;
575                 dev_watchdog_up(dev);
576         }
577         spin_unlock_bh(&dev->queue_lock);
578 }
579
580 void dev_deactivate(struct net_device *dev)
581 {
582         struct Qdisc *qdisc;
583         struct sk_buff *skb;
584         int running;
585
586         spin_lock_bh(&dev->queue_lock);
587         qdisc = dev->qdisc;
588         dev->qdisc = &noop_qdisc;
589
590         qdisc_reset(qdisc);
591
592         skb = dev->gso_skb;
593         dev->gso_skb = NULL;
594         spin_unlock_bh(&dev->queue_lock);
595
596         kfree_skb(skb);
597
598         dev_watchdog_down(dev);
599
600         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
601         synchronize_rcu();
602
603         /* Wait for outstanding qdisc_run calls. */
604         do {
605                 while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
606                         yield();
607
608                 /*
609                  * Double-check inside queue lock to ensure that all effects
610                  * of the queue run are visible when we return.
611                  */
612                 spin_lock_bh(&dev->queue_lock);
613                 running = test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
614                 spin_unlock_bh(&dev->queue_lock);
615
616                 /*
617                  * The running flag should never be set at this point because
618                  * we've already set dev->qdisc to noop_qdisc *inside* the same
619                  * pair of spin locks.  That is, if any qdisc_run starts after
620                  * our initial test it should see the noop_qdisc and then
621                  * clear the RUNNING bit before dropping the queue lock.  So
622                  * if it is set here then we've found a bug.
623                  */
624         } while (WARN_ON_ONCE(running));
625 }
626
627 void dev_init_scheduler(struct net_device *dev)
628 {
629         qdisc_lock_tree(dev);
630         dev->qdisc = &noop_qdisc;
631         dev->qdisc_sleeping = &noop_qdisc;
632         INIT_LIST_HEAD(&dev->qdisc_list);
633         qdisc_unlock_tree(dev);
634
635         setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
636 }
637
638 void dev_shutdown(struct net_device *dev)
639 {
640         struct Qdisc *qdisc;
641
642         qdisc_lock_tree(dev);
643         qdisc = dev->qdisc_sleeping;
644         dev->qdisc = &noop_qdisc;
645         dev->qdisc_sleeping = &noop_qdisc;
646         qdisc_destroy(qdisc);
647 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
648         if ((qdisc = dev->qdisc_ingress) != NULL) {
649                 dev->qdisc_ingress = NULL;
650                 qdisc_destroy(qdisc);
651         }
652 #endif
653         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
654         qdisc_unlock_tree(dev);
655 }