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 * qdisc_root_lock(qdisc) spinlock.
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.
40 static inline int qdisc_qlen(struct Qdisc *q)
45 static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
47 if (unlikely(skb->next))
50 q->ops->requeue(skb, q);
56 static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
60 if ((skb = q->gso_skb))
68 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
69 struct netdev_queue *dev_queue,
74 if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
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.
83 printk(KERN_WARNING "Dead loop on netdevice %s, "
84 "fix it urgently!\n", dev_queue->dev->name);
88 * Another cpu is holding lock, requeue & delay xmits for
91 __get_cpu_var(netdev_rx_stat).cpu_collision++;
92 ret = dev_requeue_skb(skb, q);
99 * NOTE: Called under qdisc_lock(q) with locally disabled BH.
101 * __QDISC_STATE_RUNNING guarantees only one CPU can process
102 * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
105 * netif_tx_lock serializes accesses to device driver.
107 * qdisc_lock(q) and netif_tx_lock are mutually exclusive,
108 * if one is grabbed, another must be free.
110 * Note, that this procedure can be called by a watchdog timer
112 * Returns to the caller:
113 * 0 - queue is empty or throttled.
114 * >0 - queue is not empty.
117 static inline int qdisc_restart(struct Qdisc *q)
119 struct netdev_queue *txq;
120 int ret = NETDEV_TX_BUSY;
121 struct net_device *dev;
122 spinlock_t *root_lock;
126 if (unlikely((skb = dequeue_skb(q)) == NULL))
129 root_lock = qdisc_root_lock(q);
131 /* And release qdisc */
132 spin_unlock(root_lock);
135 txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
137 HARD_TX_LOCK(dev, txq, smp_processor_id());
138 if (!netif_subqueue_stopped(dev, skb))
139 ret = dev_hard_start_xmit(skb, dev, txq);
140 HARD_TX_UNLOCK(dev, txq);
142 spin_lock(root_lock);
146 /* Driver sent out skb successfully */
150 case NETDEV_TX_LOCKED:
151 /* Driver try lock failed */
152 ret = handle_dev_cpu_collision(skb, txq, q);
156 /* Driver returned NETDEV_TX_BUSY - requeue skb */
157 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
158 printk(KERN_WARNING "BUG %s code %d qlen %d\n",
159 dev->name, ret, q->q.qlen);
161 ret = dev_requeue_skb(skb, q);
165 if (ret && netif_tx_queue_stopped(txq))
171 void __qdisc_run(struct Qdisc *q)
173 unsigned long start_time = jiffies;
175 while (qdisc_restart(q)) {
177 * Postpone processing if
178 * 1. another process needs the CPU;
179 * 2. we've been doing it for too long.
181 if (need_resched() || jiffies != start_time) {
187 clear_bit(__QDISC_STATE_RUNNING, &q->state);
190 static void dev_watchdog(unsigned long arg)
192 struct net_device *dev = (struct net_device *)arg;
195 if (!qdisc_tx_is_noop(dev)) {
196 if (netif_device_present(dev) &&
197 netif_running(dev) &&
198 netif_carrier_ok(dev)) {
199 int some_queue_stopped = 0;
202 for (i = 0; i < dev->num_tx_queues; i++) {
203 struct netdev_queue *txq;
205 txq = netdev_get_tx_queue(dev, i);
206 if (netif_tx_queue_stopped(txq)) {
207 some_queue_stopped = 1;
212 if (some_queue_stopped &&
213 time_after(jiffies, (dev->trans_start +
214 dev->watchdog_timeo))) {
215 printk(KERN_INFO "NETDEV WATCHDOG: %s: "
216 "transmit timed out\n",
218 dev->tx_timeout(dev);
221 if (!mod_timer(&dev->watchdog_timer,
222 round_jiffies(jiffies +
223 dev->watchdog_timeo)))
227 netif_tx_unlock(dev);
232 void __netdev_watchdog_up(struct net_device *dev)
234 if (dev->tx_timeout) {
235 if (dev->watchdog_timeo <= 0)
236 dev->watchdog_timeo = 5*HZ;
237 if (!mod_timer(&dev->watchdog_timer,
238 round_jiffies(jiffies + dev->watchdog_timeo)))
243 static void dev_watchdog_up(struct net_device *dev)
245 __netdev_watchdog_up(dev);
248 static void dev_watchdog_down(struct net_device *dev)
250 netif_tx_lock_bh(dev);
251 if (del_timer(&dev->watchdog_timer))
253 netif_tx_unlock_bh(dev);
257 * netif_carrier_on - set carrier
258 * @dev: network device
260 * Device has detected that carrier.
262 void netif_carrier_on(struct net_device *dev)
264 if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
265 linkwatch_fire_event(dev);
266 if (netif_running(dev))
267 __netdev_watchdog_up(dev);
270 EXPORT_SYMBOL(netif_carrier_on);
273 * netif_carrier_off - clear carrier
274 * @dev: network device
276 * Device has detected loss of carrier.
278 void netif_carrier_off(struct net_device *dev)
280 if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
281 linkwatch_fire_event(dev);
283 EXPORT_SYMBOL(netif_carrier_off);
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 __read_mostly = {
313 .enqueue = noop_enqueue,
314 .dequeue = noop_dequeue,
315 .requeue = noop_requeue,
316 .owner = THIS_MODULE,
319 static struct netdev_queue noop_netdev_queue = {
320 .qdisc = &noop_qdisc,
323 struct Qdisc noop_qdisc = {
324 .enqueue = noop_enqueue,
325 .dequeue = noop_dequeue,
326 .flags = TCQ_F_BUILTIN,
327 .ops = &noop_qdisc_ops,
328 .list = LIST_HEAD_INIT(noop_qdisc.list),
329 .q.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
330 .dev_queue = &noop_netdev_queue,
332 EXPORT_SYMBOL(noop_qdisc);
334 static struct Qdisc_ops noqueue_qdisc_ops __read_mostly = {
337 .enqueue = noop_enqueue,
338 .dequeue = noop_dequeue,
339 .requeue = noop_requeue,
340 .owner = THIS_MODULE,
343 static struct Qdisc noqueue_qdisc = {
345 .dequeue = noop_dequeue,
346 .flags = TCQ_F_BUILTIN,
347 .ops = &noqueue_qdisc_ops,
348 .list = LIST_HEAD_INIT(noqueue_qdisc.list),
352 static const u8 prio2band[TC_PRIO_MAX+1] =
353 { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
355 /* 3-band FIFO queue: old style, but should be a bit faster than
356 generic prio+fifo combination.
359 #define PFIFO_FAST_BANDS 3
361 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
364 struct sk_buff_head *list = qdisc_priv(qdisc);
365 return list + prio2band[skb->priority & TC_PRIO_MAX];
368 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
370 struct sk_buff_head *list = prio2list(skb, qdisc);
372 if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len) {
374 return __qdisc_enqueue_tail(skb, qdisc, list);
377 return qdisc_drop(skb, qdisc);
380 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
383 struct sk_buff_head *list = qdisc_priv(qdisc);
385 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
386 if (!skb_queue_empty(list + prio)) {
388 return __qdisc_dequeue_head(qdisc, list + prio);
395 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
398 return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
401 static void pfifo_fast_reset(struct Qdisc* qdisc)
404 struct sk_buff_head *list = qdisc_priv(qdisc);
406 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
407 __qdisc_reset_queue(qdisc, list + prio);
409 qdisc->qstats.backlog = 0;
413 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
415 struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
417 memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
418 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
425 static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
428 struct sk_buff_head *list = qdisc_priv(qdisc);
430 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
431 skb_queue_head_init(list + prio);
436 static struct Qdisc_ops pfifo_fast_ops __read_mostly = {
438 .priv_size = PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
439 .enqueue = pfifo_fast_enqueue,
440 .dequeue = pfifo_fast_dequeue,
441 .requeue = pfifo_fast_requeue,
442 .init = pfifo_fast_init,
443 .reset = pfifo_fast_reset,
444 .dump = pfifo_fast_dump,
445 .owner = THIS_MODULE,
448 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
449 struct Qdisc_ops *ops)
456 /* ensure that the Qdisc and the private data are 32-byte aligned */
457 size = QDISC_ALIGN(sizeof(*sch));
458 size += ops->priv_size + (QDISC_ALIGNTO - 1);
460 p = kzalloc(size, GFP_KERNEL);
463 sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
464 sch->padded = (char *) sch - (char *) p;
466 INIT_LIST_HEAD(&sch->list);
467 skb_queue_head_init(&sch->q);
469 sch->enqueue = ops->enqueue;
470 sch->dequeue = ops->dequeue;
471 sch->dev_queue = dev_queue;
472 dev_hold(qdisc_dev(sch));
473 atomic_set(&sch->refcnt, 1);
480 struct Qdisc * qdisc_create_dflt(struct net_device *dev,
481 struct netdev_queue *dev_queue,
482 struct Qdisc_ops *ops,
483 unsigned int parentid)
487 sch = qdisc_alloc(dev_queue, ops);
490 sch->parent = parentid;
492 if (!ops->init || ops->init(sch, NULL) == 0)
499 EXPORT_SYMBOL(qdisc_create_dflt);
501 /* Under qdisc_root_lock(qdisc) and BH! */
503 void qdisc_reset(struct Qdisc *qdisc)
505 const struct Qdisc_ops *ops = qdisc->ops;
510 EXPORT_SYMBOL(qdisc_reset);
512 /* this is the rcu callback function to clean up a qdisc when there
513 * are no further references to it */
515 static void __qdisc_destroy(struct rcu_head *head)
517 struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
518 const struct Qdisc_ops *ops = qdisc->ops;
520 gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
526 module_put(ops->owner);
527 dev_put(qdisc_dev(qdisc));
529 kfree_skb(qdisc->gso_skb);
531 kfree((char *) qdisc - qdisc->padded);
534 /* Under qdisc_root_lock(qdisc) and BH! */
536 void qdisc_destroy(struct Qdisc *qdisc)
538 struct net_device *dev = qdisc_dev(qdisc);
540 if (qdisc->flags & TCQ_F_BUILTIN ||
541 !atomic_dec_and_test(&qdisc->refcnt))
544 spin_lock_bh(&dev->qdisc_list_lock);
545 list_del(&qdisc->list);
546 spin_unlock_bh(&dev->qdisc_list_lock);
548 call_rcu(&qdisc->q_rcu, __qdisc_destroy);
550 EXPORT_SYMBOL(qdisc_destroy);
552 static bool dev_all_qdisc_sleeping_noop(struct net_device *dev)
556 for (i = 0; i < dev->num_tx_queues; i++) {
557 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
559 if (txq->qdisc_sleeping != &noop_qdisc)
565 static void attach_one_default_qdisc(struct net_device *dev,
566 struct netdev_queue *dev_queue,
571 if (dev->tx_queue_len) {
572 qdisc = qdisc_create_dflt(dev, dev_queue,
573 &pfifo_fast_ops, TC_H_ROOT);
575 printk(KERN_INFO "%s: activation failed\n", dev->name);
578 spin_lock_bh(&dev->qdisc_list_lock);
579 list_add_tail(&qdisc->list, &dev->qdisc_list);
580 spin_unlock_bh(&dev->qdisc_list_lock);
582 qdisc = &noqueue_qdisc;
584 dev_queue->qdisc_sleeping = qdisc;
587 static void transition_one_qdisc(struct net_device *dev,
588 struct netdev_queue *dev_queue,
589 void *_need_watchdog)
591 struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
592 int *need_watchdog_p = _need_watchdog;
594 rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
595 if (new_qdisc != &noqueue_qdisc)
596 *need_watchdog_p = 1;
599 void dev_activate(struct net_device *dev)
603 /* No queueing discipline is attached to device;
604 create default one i.e. pfifo_fast for devices,
605 which need queueing and noqueue_qdisc for
609 if (dev_all_qdisc_sleeping_noop(dev))
610 netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
612 if (!netif_carrier_ok(dev))
613 /* Delay activation until next carrier-on event */
617 netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
620 dev->trans_start = jiffies;
621 dev_watchdog_up(dev);
625 static void dev_deactivate_queue(struct net_device *dev,
626 struct netdev_queue *dev_queue,
627 void *_qdisc_default)
629 struct Qdisc *qdisc_default = _qdisc_default;
630 struct sk_buff *skb = NULL;
633 qdisc = dev_queue->qdisc;
635 spin_lock_bh(qdisc_lock(qdisc));
637 dev_queue->qdisc = qdisc_default;
640 spin_unlock_bh(qdisc_lock(qdisc));
646 static bool some_qdisc_is_running(struct net_device *dev, int lock)
650 for (i = 0; i < dev->num_tx_queues; i++) {
651 struct netdev_queue *dev_queue;
652 spinlock_t *root_lock;
656 dev_queue = netdev_get_tx_queue(dev, i);
657 q = dev_queue->qdisc;
658 root_lock = qdisc_root_lock(q);
661 spin_lock_bh(root_lock);
663 val = test_bit(__QDISC_STATE_RUNNING, &q->state);
666 spin_unlock_bh(root_lock);
674 void dev_deactivate(struct net_device *dev)
678 netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
680 dev_watchdog_down(dev);
682 /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
685 /* Wait for outstanding qdisc_run calls. */
687 while (some_qdisc_is_running(dev, 0))
691 * Double-check inside queue lock to ensure that all effects
692 * of the queue run are visible when we return.
694 running = some_qdisc_is_running(dev, 1);
697 * The running flag should never be set at this point because
698 * we've already set dev->qdisc to noop_qdisc *inside* the same
699 * pair of spin locks. That is, if any qdisc_run starts after
700 * our initial test it should see the noop_qdisc and then
701 * clear the RUNNING bit before dropping the queue lock. So
702 * if it is set here then we've found a bug.
704 } while (WARN_ON_ONCE(running));
707 static void dev_init_scheduler_queue(struct net_device *dev,
708 struct netdev_queue *dev_queue,
711 struct Qdisc *qdisc = _qdisc;
713 dev_queue->qdisc = qdisc;
714 dev_queue->qdisc_sleeping = qdisc;
717 void dev_init_scheduler(struct net_device *dev)
719 netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
720 dev_init_scheduler_queue(dev, &dev->rx_queue, NULL);
722 setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
725 static void shutdown_scheduler_queue(struct net_device *dev,
726 struct netdev_queue *dev_queue,
727 void *_qdisc_default)
729 struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
730 struct Qdisc *qdisc_default = _qdisc_default;
733 spinlock_t *root_lock = qdisc_root_lock(qdisc);
735 dev_queue->qdisc = qdisc_default;
736 dev_queue->qdisc_sleeping = qdisc_default;
738 spin_lock(root_lock);
739 qdisc_destroy(qdisc);
740 spin_unlock(root_lock);
744 void dev_shutdown(struct net_device *dev)
746 netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
747 shutdown_scheduler_queue(dev, &dev->rx_queue, NULL);
748 BUG_TRAP(!timer_pending(&dev->watchdog_timer));