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 <asm/uaccess.h>
15 #include <asm/system.h>
16 #include <linux/bitops.h>
17 #include <linux/config.h>
18 #include <linux/module.h>
19 #include <linux/types.h>
20 #include <linux/kernel.h>
21 #include <linux/sched.h>
22 #include <linux/string.h>
24 #include <linux/socket.h>
25 #include <linux/sockios.h>
27 #include <linux/errno.h>
28 #include <linux/interrupt.h>
29 #include <linux/netdevice.h>
30 #include <linux/skbuff.h>
31 #include <linux/rtnetlink.h>
32 #include <linux/init.h>
33 #include <linux/rcupdate.h>
34 #include <linux/list.h>
36 #include <net/pkt_sched.h>
38 /* Main transmission queue. */
40 /* Main qdisc structure lock.
42 However, modifications
43 to data, participating in scheduling must be additionally
44 protected with dev->queue_lock spinlock.
46 The idea is the following:
47 - enqueue, dequeue are serialized via top level device
48 spinlock dev->queue_lock.
49 - tree walking is protected by read_lock_bh(qdisc_tree_lock)
50 and this lock is used only in process context.
51 - updates to tree are made under rtnl semaphore or
52 from softirq context (__qdisc_destroy rcu-callback)
53 hence this lock needs local bh disabling.
55 qdisc_tree_lock must be grabbed BEFORE dev->queue_lock!
57 DEFINE_RWLOCK(qdisc_tree_lock);
59 void qdisc_lock_tree(struct net_device *dev)
61 write_lock_bh(&qdisc_tree_lock);
62 spin_lock_bh(&dev->queue_lock);
65 void qdisc_unlock_tree(struct net_device *dev)
67 spin_unlock_bh(&dev->queue_lock);
68 write_unlock_bh(&qdisc_tree_lock);
72 dev->queue_lock serializes queue accesses for this device
73 AND dev->qdisc pointer itself.
75 dev->xmit_lock serializes accesses to device driver.
77 dev->queue_lock and dev->xmit_lock are mutually exclusive,
78 if one is grabbed, another must be free.
83 Note, that this procedure can be called by a watchdog timer, so that
84 we do not check dev->tbusy flag here.
86 Returns: 0 - queue is empty.
87 >0 - queue is not empty, but throttled.
88 <0 - queue is not empty. Device is throttled, if dev->tbusy != 0.
90 NOTE: Called under dev->queue_lock with locally disabled BH.
93 int qdisc_restart(struct net_device *dev)
95 struct Qdisc *q = dev->qdisc;
99 if ((skb = q->dequeue(q)) != NULL) {
100 unsigned nolock = (dev->features & NETIF_F_LLTX);
102 * When the driver has LLTX set it does its own locking
103 * in start_xmit. No need to add additional overhead by
104 * locking again. These checks are worth it because
105 * even uncongested locks can be quite expensive.
106 * The driver can do trylock like here too, in case
107 * of lock congestion it should return -1 and the packet
111 if (!spin_trylock(&dev->xmit_lock)) {
113 /* So, someone grabbed the driver. */
115 /* It may be transient configuration error,
116 when hard_start_xmit() recurses. We detect
117 it by checking xmit owner and drop the
118 packet when deadloop is detected.
120 if (dev->xmit_lock_owner == smp_processor_id()) {
123 printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name);
126 __get_cpu_var(netdev_rx_stat).cpu_collision++;
129 /* Remember that the driver is grabbed by us. */
130 dev->xmit_lock_owner = smp_processor_id();
134 /* And release queue */
135 spin_unlock(&dev->queue_lock);
137 if (!netif_queue_stopped(dev)) {
140 dev_queue_xmit_nit(skb, dev);
142 ret = dev->hard_start_xmit(skb, dev);
143 if (ret == NETDEV_TX_OK) {
145 dev->xmit_lock_owner = -1;
146 spin_unlock(&dev->xmit_lock);
148 spin_lock(&dev->queue_lock);
151 if (ret == NETDEV_TX_LOCKED && nolock) {
152 spin_lock(&dev->queue_lock);
157 /* NETDEV_TX_BUSY - we need to requeue */
158 /* Release the driver */
160 dev->xmit_lock_owner = -1;
161 spin_unlock(&dev->xmit_lock);
163 spin_lock(&dev->queue_lock);
167 /* Device kicked us out :(
168 This is possible in three cases:
171 1. fastroute is enabled
172 2. device cannot determine busy state
173 before start of transmission (f.e. dialout)
174 3. device is buggy (ppp)
178 q->ops->requeue(skb, q);
182 BUG_ON((int) q->q.qlen < 0);
186 static void dev_watchdog(unsigned long arg)
188 struct net_device *dev = (struct net_device *)arg;
190 spin_lock(&dev->xmit_lock);
191 if (dev->qdisc != &noop_qdisc) {
192 if (netif_device_present(dev) &&
193 netif_running(dev) &&
194 netif_carrier_ok(dev)) {
195 if (netif_queue_stopped(dev) &&
196 (jiffies - dev->trans_start) > dev->watchdog_timeo) {
197 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n", dev->name);
198 dev->tx_timeout(dev);
200 if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
204 spin_unlock(&dev->xmit_lock);
209 static void dev_watchdog_init(struct net_device *dev)
211 init_timer(&dev->watchdog_timer);
212 dev->watchdog_timer.data = (unsigned long)dev;
213 dev->watchdog_timer.function = dev_watchdog;
216 void __netdev_watchdog_up(struct net_device *dev)
218 if (dev->tx_timeout) {
219 if (dev->watchdog_timeo <= 0)
220 dev->watchdog_timeo = 5*HZ;
221 if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
226 static void dev_watchdog_up(struct net_device *dev)
228 spin_lock_bh(&dev->xmit_lock);
229 __netdev_watchdog_up(dev);
230 spin_unlock_bh(&dev->xmit_lock);
233 static void dev_watchdog_down(struct net_device *dev)
235 spin_lock_bh(&dev->xmit_lock);
236 if (del_timer(&dev->watchdog_timer))
238 spin_unlock_bh(&dev->xmit_lock);
241 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
242 under all circumstances. It is difficult to invent anything faster or
247 noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
253 static struct sk_buff *
254 noop_dequeue(struct Qdisc * qdisc)
260 noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
263 printk(KERN_DEBUG "%s deferred output. It is buggy.\n", skb->dev->name);
268 struct Qdisc_ops noop_qdisc_ops = {
273 .enqueue = noop_enqueue,
274 .dequeue = noop_dequeue,
275 .requeue = noop_requeue,
276 .owner = THIS_MODULE,
279 struct Qdisc noop_qdisc = {
280 .enqueue = noop_enqueue,
281 .dequeue = noop_dequeue,
282 .flags = TCQ_F_BUILTIN,
283 .ops = &noop_qdisc_ops,
284 .list = LIST_HEAD_INIT(noop_qdisc.list),
287 static struct Qdisc_ops noqueue_qdisc_ops = {
292 .enqueue = noop_enqueue,
293 .dequeue = noop_dequeue,
294 .requeue = noop_requeue,
295 .owner = THIS_MODULE,
298 static struct Qdisc noqueue_qdisc = {
300 .dequeue = noop_dequeue,
301 .flags = TCQ_F_BUILTIN,
302 .ops = &noqueue_qdisc_ops,
303 .list = LIST_HEAD_INIT(noqueue_qdisc.list),
307 static const u8 prio2band[TC_PRIO_MAX+1] =
308 { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
310 /* 3-band FIFO queue: old style, but should be a bit faster than
311 generic prio+fifo combination.
315 pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
317 struct sk_buff_head *list = qdisc_priv(qdisc);
319 list += prio2band[skb->priority&TC_PRIO_MAX];
321 if (list->qlen < qdisc->dev->tx_queue_len) {
322 __skb_queue_tail(list, skb);
324 qdisc->bstats.bytes += skb->len;
325 qdisc->bstats.packets++;
328 qdisc->qstats.drops++;
330 return NET_XMIT_DROP;
333 static struct sk_buff *
334 pfifo_fast_dequeue(struct Qdisc* qdisc)
337 struct sk_buff_head *list = qdisc_priv(qdisc);
340 for (prio = 0; prio < 3; prio++, list++) {
341 skb = __skb_dequeue(list);
351 pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
353 struct sk_buff_head *list = qdisc_priv(qdisc);
355 list += prio2band[skb->priority&TC_PRIO_MAX];
357 __skb_queue_head(list, skb);
359 qdisc->qstats.requeues++;
364 pfifo_fast_reset(struct Qdisc* qdisc)
367 struct sk_buff_head *list = qdisc_priv(qdisc);
369 for (prio=0; prio < 3; prio++)
370 skb_queue_purge(list+prio);
374 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
376 unsigned char *b = skb->tail;
377 struct tc_prio_qopt opt;
380 memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
381 RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
385 skb_trim(skb, b - skb->data);
389 static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
392 struct sk_buff_head *list = qdisc_priv(qdisc);
395 skb_queue_head_init(list+i);
400 static struct Qdisc_ops pfifo_fast_ops = {
404 .priv_size = 3 * sizeof(struct sk_buff_head),
405 .enqueue = pfifo_fast_enqueue,
406 .dequeue = pfifo_fast_dequeue,
407 .requeue = pfifo_fast_requeue,
408 .init = pfifo_fast_init,
409 .reset = pfifo_fast_reset,
410 .dump = pfifo_fast_dump,
411 .owner = THIS_MODULE,
414 struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops)
420 /* ensure that the Qdisc and the private data are 32-byte aligned */
421 size = ((sizeof(*sch) + QDISC_ALIGN_CONST) & ~QDISC_ALIGN_CONST);
422 size += ops->priv_size + QDISC_ALIGN_CONST;
424 p = kmalloc(size, GFP_KERNEL);
429 sch = (struct Qdisc *)(((unsigned long)p + QDISC_ALIGN_CONST)
430 & ~QDISC_ALIGN_CONST);
431 sch->padded = (char *)sch - (char *)p;
433 INIT_LIST_HEAD(&sch->list);
434 skb_queue_head_init(&sch->q);
436 sch->enqueue = ops->enqueue;
437 sch->dequeue = ops->dequeue;
440 sch->stats_lock = &dev->queue_lock;
441 atomic_set(&sch->refcnt, 1);
442 if (!ops->init || ops->init(sch, NULL) == 0)
450 /* Under dev->queue_lock and BH! */
452 void qdisc_reset(struct Qdisc *qdisc)
454 struct Qdisc_ops *ops = qdisc->ops;
460 /* this is the rcu callback function to clean up a qdisc when there
461 * are no further references to it */
463 static void __qdisc_destroy(struct rcu_head *head)
465 struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
466 struct Qdisc_ops *ops = qdisc->ops;
468 #ifdef CONFIG_NET_ESTIMATOR
469 gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
471 write_lock(&qdisc_tree_lock);
476 write_unlock(&qdisc_tree_lock);
477 module_put(ops->owner);
480 kfree((char *) qdisc - qdisc->padded);
483 /* Under dev->queue_lock and BH! */
485 void qdisc_destroy(struct Qdisc *qdisc)
487 struct list_head cql = LIST_HEAD_INIT(cql);
488 struct Qdisc *cq, *q, *n;
490 if (qdisc->flags & TCQ_F_BUILTIN ||
491 !atomic_dec_and_test(&qdisc->refcnt))
494 if (!list_empty(&qdisc->list)) {
495 if (qdisc->ops->cl_ops == NULL)
496 list_del(&qdisc->list);
498 list_move(&qdisc->list, &cql);
501 /* unlink inner qdiscs from dev->qdisc_list immediately */
502 list_for_each_entry(cq, &cql, list)
503 list_for_each_entry_safe(q, n, &qdisc->dev->qdisc_list, list)
504 if (TC_H_MAJ(q->parent) == TC_H_MAJ(cq->handle)) {
505 if (q->ops->cl_ops == NULL)
506 list_del_init(&q->list);
508 list_move_tail(&q->list, &cql);
510 list_for_each_entry_safe(cq, n, &cql, list)
511 list_del_init(&cq->list);
513 call_rcu(&qdisc->q_rcu, __qdisc_destroy);
516 void dev_activate(struct net_device *dev)
518 /* No queueing discipline is attached to device;
519 create default one i.e. pfifo_fast for devices,
520 which need queueing and noqueue_qdisc for
524 if (dev->qdisc_sleeping == &noop_qdisc) {
526 if (dev->tx_queue_len) {
527 qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops);
529 printk(KERN_INFO "%s: activation failed\n", dev->name);
532 write_lock_bh(&qdisc_tree_lock);
533 list_add_tail(&qdisc->list, &dev->qdisc_list);
534 write_unlock_bh(&qdisc_tree_lock);
536 qdisc = &noqueue_qdisc;
538 write_lock_bh(&qdisc_tree_lock);
539 dev->qdisc_sleeping = qdisc;
540 write_unlock_bh(&qdisc_tree_lock);
543 if (!netif_carrier_ok(dev))
544 /* Delay activation until next carrier-on event */
547 spin_lock_bh(&dev->queue_lock);
548 rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
549 if (dev->qdisc != &noqueue_qdisc) {
550 dev->trans_start = jiffies;
551 dev_watchdog_up(dev);
553 spin_unlock_bh(&dev->queue_lock);
556 void dev_deactivate(struct net_device *dev)
560 spin_lock_bh(&dev->queue_lock);
562 dev->qdisc = &noop_qdisc;
566 spin_unlock_bh(&dev->queue_lock);
568 dev_watchdog_down(dev);
570 while (test_bit(__LINK_STATE_SCHED, &dev->state))
573 spin_unlock_wait(&dev->xmit_lock);
576 void dev_init_scheduler(struct net_device *dev)
578 qdisc_lock_tree(dev);
579 dev->qdisc = &noop_qdisc;
580 dev->qdisc_sleeping = &noop_qdisc;
581 INIT_LIST_HEAD(&dev->qdisc_list);
582 qdisc_unlock_tree(dev);
584 dev_watchdog_init(dev);
587 void dev_shutdown(struct net_device *dev)
591 qdisc_lock_tree(dev);
592 qdisc = dev->qdisc_sleeping;
593 dev->qdisc = &noop_qdisc;
594 dev->qdisc_sleeping = &noop_qdisc;
595 qdisc_destroy(qdisc);
596 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
597 if ((qdisc = dev->qdisc_ingress) != NULL) {
598 dev->qdisc_ingress = NULL;
599 qdisc_destroy(qdisc);
602 BUG_TRAP(!timer_pending(&dev->watchdog_timer));
603 qdisc_unlock_tree(dev);
606 EXPORT_SYMBOL(__netdev_watchdog_up);
607 EXPORT_SYMBOL(noop_qdisc);
608 EXPORT_SYMBOL(noop_qdisc_ops);
609 EXPORT_SYMBOL(qdisc_create_dflt);
610 EXPORT_SYMBOL(qdisc_destroy);
611 EXPORT_SYMBOL(qdisc_reset);
612 EXPORT_SYMBOL(qdisc_restart);
613 EXPORT_SYMBOL(qdisc_lock_tree);
614 EXPORT_SYMBOL(qdisc_unlock_tree);