2 * net/sched/sch_generic.c Generic packet scheduler routines.
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.
9 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10 * Jamal Hadi Salim, <hadi@cyberus.ca> 990601
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>
29 /* Main transmission queue. */
31 /* Modifications to data participating in scheduling must be protected with
32 * dev->queue_lock spinlock.
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.
42 void qdisc_lock_tree(struct net_device *dev)
44 spin_lock_bh(&dev->queue_lock);
45 spin_lock(&dev->ingress_lock);
48 void qdisc_unlock_tree(struct net_device *dev)
50 spin_unlock(&dev->ingress_lock);
51 spin_unlock_bh(&dev->queue_lock);
54 static inline int qdisc_qlen(struct Qdisc *q)
59 static inline int dev_requeue_skb(struct sk_buff *skb, struct net_device *dev,
62 if (unlikely(skb->next))
65 q->ops->requeue(skb, q);
71 static inline struct sk_buff *dev_dequeue_skb(struct net_device *dev,
76 if ((skb = dev->gso_skb))
84 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
85 struct net_device *dev,
90 if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
92 * Same CPU holding the lock. It may be a transient
93 * configuration error, when hard_start_xmit() recurses. We
94 * detect it by checking xmit owner and drop the packet when
95 * deadloop is detected. Return OK to try the next skb.
99 printk(KERN_WARNING "Dead loop on netdevice %s, "
100 "fix it urgently!\n", dev->name);
104 * Another cpu is holding lock, requeue & delay xmits for
107 __get_cpu_var(netdev_rx_stat).cpu_collision++;
108 ret = dev_requeue_skb(skb, dev, q);
115 * NOTE: Called under dev->queue_lock with locally disabled BH.
117 * __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
118 * device at a time. dev->queue_lock serializes queue accesses for
119 * this device AND dev->qdisc pointer itself.
121 * netif_tx_lock serializes accesses to device driver.
123 * dev->queue_lock and netif_tx_lock are mutually exclusive,
124 * if one is grabbed, another must be free.
126 * Note, that this procedure can be called by a watchdog timer
128 * Returns to the caller:
129 * 0 - queue is empty or throttled.
130 * >0 - queue is not empty.
133 static inline int qdisc_restart(struct net_device *dev)
135 struct Qdisc *q = dev->qdisc;
141 if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
145 * When the driver has LLTX set, it does its own locking in
146 * start_xmit. These checks are worth it because even uncongested
147 * locks can be quite expensive. The driver can do a trylock, as
148 * is being done here; in case of lock contention it should return
149 * NETDEV_TX_LOCKED and the packet will be requeued.
151 lockless = (dev->features & NETIF_F_LLTX);
153 if (!lockless && !netif_tx_trylock(dev)) {
154 /* Another CPU grabbed the driver tx lock */
155 return handle_dev_cpu_collision(skb, dev, q);
158 /* And release queue */
159 spin_unlock(&dev->queue_lock);
161 ret = dev_hard_start_xmit(skb, dev);
164 netif_tx_unlock(dev);
166 spin_lock(&dev->queue_lock);
171 /* Driver sent out skb successfully */
175 case NETDEV_TX_LOCKED:
176 /* Driver try lock failed */
177 ret = handle_dev_cpu_collision(skb, dev, q);
181 /* Driver returned NETDEV_TX_BUSY - requeue skb */
182 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
183 printk(KERN_WARNING "BUG %s code %d qlen %d\n",
184 dev->name, ret, q->q.qlen);
186 ret = dev_requeue_skb(skb, dev, q);
193 void __qdisc_run(struct net_device *dev)
196 if (!qdisc_restart(dev))
198 } while (!netif_queue_stopped(dev));
200 clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
203 static void dev_watchdog(unsigned long arg)
205 struct net_device *dev = (struct net_device *)arg;
208 if (dev->qdisc != &noop_qdisc) {
209 if (netif_device_present(dev) &&
210 netif_running(dev) &&
211 netif_carrier_ok(dev)) {
212 if (netif_queue_stopped(dev) &&
213 time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {
215 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
217 dev->tx_timeout(dev);
219 if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo)))
223 netif_tx_unlock(dev);
228 static void dev_watchdog_init(struct net_device *dev)
230 init_timer(&dev->watchdog_timer);
231 dev->watchdog_timer.data = (unsigned long)dev;
232 dev->watchdog_timer.function = dev_watchdog;
235 void __netdev_watchdog_up(struct net_device *dev)
237 if (dev->tx_timeout) {
238 if (dev->watchdog_timeo <= 0)
239 dev->watchdog_timeo = 5*HZ;
240 if (!mod_timer(&dev->watchdog_timer,
241 round_jiffies(jiffies + dev->watchdog_timeo)))
246 static void dev_watchdog_up(struct net_device *dev)
248 __netdev_watchdog_up(dev);
251 static void dev_watchdog_down(struct net_device *dev)
253 netif_tx_lock_bh(dev);
254 if (del_timer(&dev->watchdog_timer))
256 netif_tx_unlock_bh(dev);
260 * netif_carrier_on - set carrier
261 * @dev: network device
263 * Device has detected that carrier.
265 void netif_carrier_on(struct net_device *dev)
267 if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state))
268 linkwatch_fire_event(dev);
269 if (netif_running(dev))
270 __netdev_watchdog_up(dev);
274 * netif_carrier_off - clear carrier
275 * @dev: network device
277 * Device has detected loss of carrier.
279 void netif_carrier_off(struct net_device *dev)
281 if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
282 linkwatch_fire_event(dev);
285 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
286 under all circumstances. It is difficult to invent anything faster or
290 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
296 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
301 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
304 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
310 struct Qdisc_ops noop_qdisc_ops = {
313 .enqueue = noop_enqueue,
314 .dequeue = noop_dequeue,
315 .requeue = noop_requeue,
316 .owner = THIS_MODULE,
319 struct Qdisc noop_qdisc = {
320 .enqueue = noop_enqueue,
321 .dequeue = noop_dequeue,
322 .flags = TCQ_F_BUILTIN,
323 .ops = &noop_qdisc_ops,
324 .list = LIST_HEAD_INIT(noop_qdisc.list),
327 static struct Qdisc_ops noqueue_qdisc_ops = {
330 .enqueue = noop_enqueue,
331 .dequeue = noop_dequeue,
332 .requeue = noop_requeue,
333 .owner = THIS_MODULE,
336 static struct Qdisc noqueue_qdisc = {
338 .dequeue = noop_dequeue,
339 .flags = TCQ_F_BUILTIN,
340 .ops = &noqueue_qdisc_ops,
341 .list = LIST_HEAD_INIT(noqueue_qdisc.list),
345 static const u8 prio2band[TC_PRIO_MAX+1] =
346 { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
348 /* 3-band FIFO queue: old style, but should be a bit faster than
349 generic prio+fifo combination.
352 #define PFIFO_FAST_BANDS 3
354 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
357 struct sk_buff_head *list = qdisc_priv(qdisc);
358 return list + prio2band[skb->priority & TC_PRIO_MAX];
361 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
363 struct sk_buff_head *list = prio2list(skb, qdisc);
365 if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
367 return __qdisc_enqueue_tail(skb, qdisc, list);
370 return qdisc_drop(skb, qdisc);
373 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
376 struct sk_buff_head *list = qdisc_priv(qdisc);
378 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
379 if (!skb_queue_empty(list + prio)) {
381 return __qdisc_dequeue_head(qdisc, list + prio);
388 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
391 return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
394 static void pfifo_fast_reset(struct Qdisc* qdisc)
397 struct sk_buff_head *list = qdisc_priv(qdisc);
399 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
400 __qdisc_reset_queue(qdisc, list + prio);
402 qdisc->qstats.backlog = 0;
406 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
408 struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
410 memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
411 RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
418 static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
421 struct sk_buff_head *list = qdisc_priv(qdisc);
423 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
424 skb_queue_head_init(list + prio);
429 static struct Qdisc_ops pfifo_fast_ops = {
431 .priv_size = PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
432 .enqueue = pfifo_fast_enqueue,
433 .dequeue = pfifo_fast_dequeue,
434 .requeue = pfifo_fast_requeue,
435 .init = pfifo_fast_init,
436 .reset = pfifo_fast_reset,
437 .dump = pfifo_fast_dump,
438 .owner = THIS_MODULE,
441 struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops)
448 /* ensure that the Qdisc and the private data are 32-byte aligned */
449 size = QDISC_ALIGN(sizeof(*sch));
450 size += ops->priv_size + (QDISC_ALIGNTO - 1);
452 p = kzalloc(size, GFP_KERNEL);
455 sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
456 sch->padded = (char *) sch - (char *) p;
458 INIT_LIST_HEAD(&sch->list);
459 skb_queue_head_init(&sch->q);
461 sch->enqueue = ops->enqueue;
462 sch->dequeue = ops->dequeue;
465 atomic_set(&sch->refcnt, 1);
469 return ERR_PTR(-err);
472 struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops,
473 unsigned int parentid)
477 sch = qdisc_alloc(dev, ops);
480 sch->stats_lock = &dev->queue_lock;
481 sch->parent = parentid;
483 if (!ops->init || ops->init(sch, NULL) == 0)
491 /* Under dev->queue_lock and BH! */
493 void qdisc_reset(struct Qdisc *qdisc)
495 struct Qdisc_ops *ops = qdisc->ops;
501 /* this is the rcu callback function to clean up a qdisc when there
502 * are no further references to it */
504 static void __qdisc_destroy(struct rcu_head *head)
506 struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
507 kfree((char *) qdisc - qdisc->padded);
510 /* Under dev->queue_lock and BH! */
512 void qdisc_destroy(struct Qdisc *qdisc)
514 struct Qdisc_ops *ops = qdisc->ops;
516 if (qdisc->flags & TCQ_F_BUILTIN ||
517 !atomic_dec_and_test(&qdisc->refcnt))
520 list_del(&qdisc->list);
521 gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
527 module_put(ops->owner);
529 call_rcu(&qdisc->q_rcu, __qdisc_destroy);
532 void dev_activate(struct net_device *dev)
534 /* No queueing discipline is attached to device;
535 create default one i.e. pfifo_fast for devices,
536 which need queueing and noqueue_qdisc for
540 if (dev->qdisc_sleeping == &noop_qdisc) {
542 if (dev->tx_queue_len) {
543 qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops,
546 printk(KERN_INFO "%s: activation failed\n", dev->name);
549 list_add_tail(&qdisc->list, &dev->qdisc_list);
551 qdisc = &noqueue_qdisc;
553 dev->qdisc_sleeping = qdisc;
556 if (!netif_carrier_ok(dev))
557 /* Delay activation until next carrier-on event */
560 spin_lock_bh(&dev->queue_lock);
561 rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
562 if (dev->qdisc != &noqueue_qdisc) {
563 dev->trans_start = jiffies;
564 dev_watchdog_up(dev);
566 spin_unlock_bh(&dev->queue_lock);
569 void dev_deactivate(struct net_device *dev)
574 spin_lock_bh(&dev->queue_lock);
576 dev->qdisc = &noop_qdisc;
582 spin_unlock_bh(&dev->queue_lock);
586 dev_watchdog_down(dev);
588 /* Wait for outstanding dev_queue_xmit calls. */
591 /* Wait for outstanding qdisc_run calls. */
592 while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
596 void dev_init_scheduler(struct net_device *dev)
598 qdisc_lock_tree(dev);
599 dev->qdisc = &noop_qdisc;
600 dev->qdisc_sleeping = &noop_qdisc;
601 INIT_LIST_HEAD(&dev->qdisc_list);
602 qdisc_unlock_tree(dev);
604 dev_watchdog_init(dev);
607 void dev_shutdown(struct net_device *dev)
611 qdisc_lock_tree(dev);
612 qdisc = dev->qdisc_sleeping;
613 dev->qdisc = &noop_qdisc;
614 dev->qdisc_sleeping = &noop_qdisc;
615 qdisc_destroy(qdisc);
616 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
617 if ((qdisc = dev->qdisc_ingress) != NULL) {
618 dev->qdisc_ingress = NULL;
619 qdisc_destroy(qdisc);
622 BUG_TRAP(!timer_pending(&dev->watchdog_timer));
623 qdisc_unlock_tree(dev);
626 EXPORT_SYMBOL(netif_carrier_on);
627 EXPORT_SYMBOL(netif_carrier_off);
628 EXPORT_SYMBOL(noop_qdisc);
629 EXPORT_SYMBOL(qdisc_create_dflt);
630 EXPORT_SYMBOL(qdisc_destroy);
631 EXPORT_SYMBOL(qdisc_reset);
632 EXPORT_SYMBOL(qdisc_lock_tree);
633 EXPORT_SYMBOL(qdisc_unlock_tree);