[PKT_SCHED]: noop/noqueue qdisc style cleanups
[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 <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>
23 #include <linux/mm.h>
24 #include <linux/socket.h>
25 #include <linux/sockios.h>
26 #include <linux/in.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>
35 #include <net/sock.h>
36 #include <net/pkt_sched.h>
37
38 /* Main transmission queue. */
39
40 /* Main qdisc structure lock. 
41
42    However, modifications
43    to data, participating in scheduling must be additionally
44    protected with dev->queue_lock spinlock.
45
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.
54
55    qdisc_tree_lock must be grabbed BEFORE dev->queue_lock!
56  */
57 DEFINE_RWLOCK(qdisc_tree_lock);
58
59 void qdisc_lock_tree(struct net_device *dev)
60 {
61         write_lock_bh(&qdisc_tree_lock);
62         spin_lock_bh(&dev->queue_lock);
63 }
64
65 void qdisc_unlock_tree(struct net_device *dev)
66 {
67         spin_unlock_bh(&dev->queue_lock);
68         write_unlock_bh(&qdisc_tree_lock);
69 }
70
71 /* 
72    dev->queue_lock serializes queue accesses for this device
73    AND dev->qdisc pointer itself.
74
75    dev->xmit_lock serializes accesses to device driver.
76
77    dev->queue_lock and dev->xmit_lock are mutually exclusive,
78    if one is grabbed, another must be free.
79  */
80
81
82 /* Kick device.
83    Note, that this procedure can be called by a watchdog timer, so that
84    we do not check dev->tbusy flag here.
85
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.
89
90    NOTE: Called under dev->queue_lock with locally disabled BH.
91 */
92
93 int qdisc_restart(struct net_device *dev)
94 {
95         struct Qdisc *q = dev->qdisc;
96         struct sk_buff *skb;
97
98         /* Dequeue packet */
99         if ((skb = q->dequeue(q)) != NULL) {
100                 unsigned nolock = (dev->features & NETIF_F_LLTX);
101                 /*
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
108                  * will be requeued.
109                  */
110                 if (!nolock) {
111                         if (!spin_trylock(&dev->xmit_lock)) {
112                         collision:
113                                 /* So, someone grabbed the driver. */
114                                 
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.
119                                 */
120                                 if (dev->xmit_lock_owner == smp_processor_id()) {
121                                         kfree_skb(skb);
122                                         if (net_ratelimit())
123                                                 printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name);
124                                         return -1;
125                                 }
126                                 __get_cpu_var(netdev_rx_stat).cpu_collision++;
127                                 goto requeue;
128                         }
129                         /* Remember that the driver is grabbed by us. */
130                         dev->xmit_lock_owner = smp_processor_id();
131                 }
132                 
133                 {
134                         /* And release queue */
135                         spin_unlock(&dev->queue_lock);
136
137                         if (!netif_queue_stopped(dev)) {
138                                 int ret;
139                                 if (netdev_nit)
140                                         dev_queue_xmit_nit(skb, dev);
141
142                                 ret = dev->hard_start_xmit(skb, dev);
143                                 if (ret == NETDEV_TX_OK) { 
144                                         if (!nolock) {
145                                                 dev->xmit_lock_owner = -1;
146                                                 spin_unlock(&dev->xmit_lock);
147                                         }
148                                         spin_lock(&dev->queue_lock);
149                                         return -1;
150                                 }
151                                 if (ret == NETDEV_TX_LOCKED && nolock) {
152                                         spin_lock(&dev->queue_lock);
153                                         goto collision; 
154                                 }
155                         }
156
157                         /* NETDEV_TX_BUSY - we need to requeue */
158                         /* Release the driver */
159                         if (!nolock) { 
160                                 dev->xmit_lock_owner = -1;
161                                 spin_unlock(&dev->xmit_lock);
162                         } 
163                         spin_lock(&dev->queue_lock);
164                         q = dev->qdisc;
165                 }
166
167                 /* Device kicked us out :(
168                    This is possible in three cases:
169
170                    0. driver is locked
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)
175                  */
176
177 requeue:
178                 q->ops->requeue(skb, q);
179                 netif_schedule(dev);
180                 return 1;
181         }
182         BUG_ON((int) q->q.qlen < 0);
183         return q->q.qlen;
184 }
185
186 static void dev_watchdog(unsigned long arg)
187 {
188         struct net_device *dev = (struct net_device *)arg;
189
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);
199                         }
200                         if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
201                                 dev_hold(dev);
202                 }
203         }
204         spin_unlock(&dev->xmit_lock);
205
206         dev_put(dev);
207 }
208
209 static void dev_watchdog_init(struct net_device *dev)
210 {
211         init_timer(&dev->watchdog_timer);
212         dev->watchdog_timer.data = (unsigned long)dev;
213         dev->watchdog_timer.function = dev_watchdog;
214 }
215
216 void __netdev_watchdog_up(struct net_device *dev)
217 {
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))
222                         dev_hold(dev);
223         }
224 }
225
226 static void dev_watchdog_up(struct net_device *dev)
227 {
228         spin_lock_bh(&dev->xmit_lock);
229         __netdev_watchdog_up(dev);
230         spin_unlock_bh(&dev->xmit_lock);
231 }
232
233 static void dev_watchdog_down(struct net_device *dev)
234 {
235         spin_lock_bh(&dev->xmit_lock);
236         if (del_timer(&dev->watchdog_timer))
237                 __dev_put(dev);
238         spin_unlock_bh(&dev->xmit_lock);
239 }
240
241 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
242    under all circumstances. It is difficult to invent anything faster or
243    cheaper.
244  */
245
246 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
247 {
248         kfree_skb(skb);
249         return NET_XMIT_CN;
250 }
251
252 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
253 {
254         return NULL;
255 }
256
257 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
258 {
259         if (net_ratelimit())
260                 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
261                        skb->dev->name);
262         kfree_skb(skb);
263         return NET_XMIT_CN;
264 }
265
266 struct Qdisc_ops noop_qdisc_ops = {
267         .id             =       "noop",
268         .priv_size      =       0,
269         .enqueue        =       noop_enqueue,
270         .dequeue        =       noop_dequeue,
271         .requeue        =       noop_requeue,
272         .owner          =       THIS_MODULE,
273 };
274
275 struct Qdisc noop_qdisc = {
276         .enqueue        =       noop_enqueue,
277         .dequeue        =       noop_dequeue,
278         .flags          =       TCQ_F_BUILTIN,
279         .ops            =       &noop_qdisc_ops,        
280         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
281 };
282
283 static struct Qdisc_ops noqueue_qdisc_ops = {
284         .id             =       "noqueue",
285         .priv_size      =       0,
286         .enqueue        =       noop_enqueue,
287         .dequeue        =       noop_dequeue,
288         .requeue        =       noop_requeue,
289         .owner          =       THIS_MODULE,
290 };
291
292 static struct Qdisc noqueue_qdisc = {
293         .enqueue        =       NULL,
294         .dequeue        =       noop_dequeue,
295         .flags          =       TCQ_F_BUILTIN,
296         .ops            =       &noqueue_qdisc_ops,
297         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
298 };
299
300
301 static const u8 prio2band[TC_PRIO_MAX+1] =
302         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
303
304 /* 3-band FIFO queue: old style, but should be a bit faster than
305    generic prio+fifo combination.
306  */
307
308 #define PFIFO_FAST_BANDS 3
309
310 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
311                                              struct Qdisc *qdisc)
312 {
313         struct sk_buff_head *list = qdisc_priv(qdisc);
314         return list + prio2band[skb->priority & TC_PRIO_MAX];
315 }
316
317 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
318 {
319         struct sk_buff_head *list = prio2list(skb, qdisc);
320
321         if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
322                 qdisc->q.qlen++;
323                 return __qdisc_enqueue_tail(skb, qdisc, list);
324         }
325
326         return qdisc_drop(skb, qdisc);
327 }
328
329 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
330 {
331         int prio;
332         struct sk_buff_head *list = qdisc_priv(qdisc);
333
334         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++, list++) {
335                 struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list);
336                 if (skb) {
337                         qdisc->q.qlen--;
338                         return skb;
339                 }
340         }
341
342         return NULL;
343 }
344
345 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
346 {
347         qdisc->q.qlen++;
348         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
349 }
350
351 static void pfifo_fast_reset(struct Qdisc* qdisc)
352 {
353         int prio;
354         struct sk_buff_head *list = qdisc_priv(qdisc);
355
356         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
357                 __qdisc_reset_queue(qdisc, list + prio);
358
359         qdisc->qstats.backlog = 0;
360         qdisc->q.qlen = 0;
361 }
362
363 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
364 {
365         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
366
367         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
368         RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
369         return skb->len;
370
371 rtattr_failure:
372         return -1;
373 }
374
375 static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
376 {
377         int prio;
378         struct sk_buff_head *list = qdisc_priv(qdisc);
379
380         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
381                 skb_queue_head_init(list + prio);
382
383         return 0;
384 }
385
386 static struct Qdisc_ops pfifo_fast_ops = {
387         .id             =       "pfifo_fast",
388         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
389         .enqueue        =       pfifo_fast_enqueue,
390         .dequeue        =       pfifo_fast_dequeue,
391         .requeue        =       pfifo_fast_requeue,
392         .init           =       pfifo_fast_init,
393         .reset          =       pfifo_fast_reset,
394         .dump           =       pfifo_fast_dump,
395         .owner          =       THIS_MODULE,
396 };
397
398 struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops)
399 {
400         void *p;
401         struct Qdisc *sch;
402         int size;
403
404         /* ensure that the Qdisc and the private data are 32-byte aligned */
405         size = ((sizeof(*sch) + QDISC_ALIGN_CONST) & ~QDISC_ALIGN_CONST);
406         size += ops->priv_size + QDISC_ALIGN_CONST;
407
408         p = kmalloc(size, GFP_KERNEL);
409         if (!p)
410                 return NULL;
411         memset(p, 0, size);
412
413         sch = (struct Qdisc *)(((unsigned long)p + QDISC_ALIGN_CONST) 
414                                & ~QDISC_ALIGN_CONST);
415         sch->padded = (char *)sch - (char *)p;
416
417         INIT_LIST_HEAD(&sch->list);
418         skb_queue_head_init(&sch->q);
419         sch->ops = ops;
420         sch->enqueue = ops->enqueue;
421         sch->dequeue = ops->dequeue;
422         sch->dev = dev;
423         dev_hold(dev);
424         sch->stats_lock = &dev->queue_lock;
425         atomic_set(&sch->refcnt, 1);
426         if (!ops->init || ops->init(sch, NULL) == 0)
427                 return sch;
428
429         dev_put(dev);
430         kfree(p);
431         return NULL;
432 }
433
434 /* Under dev->queue_lock and BH! */
435
436 void qdisc_reset(struct Qdisc *qdisc)
437 {
438         struct Qdisc_ops *ops = qdisc->ops;
439
440         if (ops->reset)
441                 ops->reset(qdisc);
442 }
443
444 /* this is the rcu callback function to clean up a qdisc when there 
445  * are no further references to it */
446
447 static void __qdisc_destroy(struct rcu_head *head)
448 {
449         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
450         struct Qdisc_ops  *ops = qdisc->ops;
451
452 #ifdef CONFIG_NET_ESTIMATOR
453         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
454 #endif
455         write_lock(&qdisc_tree_lock);
456         if (ops->reset)
457                 ops->reset(qdisc);
458         if (ops->destroy)
459                 ops->destroy(qdisc);
460         write_unlock(&qdisc_tree_lock);
461         module_put(ops->owner);
462
463         dev_put(qdisc->dev);
464         kfree((char *) qdisc - qdisc->padded);
465 }
466
467 /* Under dev->queue_lock and BH! */
468
469 void qdisc_destroy(struct Qdisc *qdisc)
470 {
471         struct list_head cql = LIST_HEAD_INIT(cql);
472         struct Qdisc *cq, *q, *n;
473
474         if (qdisc->flags & TCQ_F_BUILTIN ||
475                 !atomic_dec_and_test(&qdisc->refcnt))
476                 return;
477
478         if (!list_empty(&qdisc->list)) {
479                 if (qdisc->ops->cl_ops == NULL)
480                         list_del(&qdisc->list);
481                 else
482                         list_move(&qdisc->list, &cql);
483         }
484
485         /* unlink inner qdiscs from dev->qdisc_list immediately */
486         list_for_each_entry(cq, &cql, list)
487                 list_for_each_entry_safe(q, n, &qdisc->dev->qdisc_list, list)
488                         if (TC_H_MAJ(q->parent) == TC_H_MAJ(cq->handle)) {
489                                 if (q->ops->cl_ops == NULL)
490                                         list_del_init(&q->list);
491                                 else
492                                         list_move_tail(&q->list, &cql);
493                         }
494         list_for_each_entry_safe(cq, n, &cql, list)
495                 list_del_init(&cq->list);
496
497         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
498 }
499
500 void dev_activate(struct net_device *dev)
501 {
502         /* No queueing discipline is attached to device;
503            create default one i.e. pfifo_fast for devices,
504            which need queueing and noqueue_qdisc for
505            virtual interfaces
506          */
507
508         if (dev->qdisc_sleeping == &noop_qdisc) {
509                 struct Qdisc *qdisc;
510                 if (dev->tx_queue_len) {
511                         qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops);
512                         if (qdisc == NULL) {
513                                 printk(KERN_INFO "%s: activation failed\n", dev->name);
514                                 return;
515                         }
516                         write_lock_bh(&qdisc_tree_lock);
517                         list_add_tail(&qdisc->list, &dev->qdisc_list);
518                         write_unlock_bh(&qdisc_tree_lock);
519                 } else {
520                         qdisc =  &noqueue_qdisc;
521                 }
522                 write_lock_bh(&qdisc_tree_lock);
523                 dev->qdisc_sleeping = qdisc;
524                 write_unlock_bh(&qdisc_tree_lock);
525         }
526
527         if (!netif_carrier_ok(dev))
528                 /* Delay activation until next carrier-on event */
529                 return;
530
531         spin_lock_bh(&dev->queue_lock);
532         rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
533         if (dev->qdisc != &noqueue_qdisc) {
534                 dev->trans_start = jiffies;
535                 dev_watchdog_up(dev);
536         }
537         spin_unlock_bh(&dev->queue_lock);
538 }
539
540 void dev_deactivate(struct net_device *dev)
541 {
542         struct Qdisc *qdisc;
543
544         spin_lock_bh(&dev->queue_lock);
545         qdisc = dev->qdisc;
546         dev->qdisc = &noop_qdisc;
547
548         qdisc_reset(qdisc);
549
550         spin_unlock_bh(&dev->queue_lock);
551
552         dev_watchdog_down(dev);
553
554         while (test_bit(__LINK_STATE_SCHED, &dev->state))
555                 yield();
556
557         spin_unlock_wait(&dev->xmit_lock);
558 }
559
560 void dev_init_scheduler(struct net_device *dev)
561 {
562         qdisc_lock_tree(dev);
563         dev->qdisc = &noop_qdisc;
564         dev->qdisc_sleeping = &noop_qdisc;
565         INIT_LIST_HEAD(&dev->qdisc_list);
566         qdisc_unlock_tree(dev);
567
568         dev_watchdog_init(dev);
569 }
570
571 void dev_shutdown(struct net_device *dev)
572 {
573         struct Qdisc *qdisc;
574
575         qdisc_lock_tree(dev);
576         qdisc = dev->qdisc_sleeping;
577         dev->qdisc = &noop_qdisc;
578         dev->qdisc_sleeping = &noop_qdisc;
579         qdisc_destroy(qdisc);
580 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
581         if ((qdisc = dev->qdisc_ingress) != NULL) {
582                 dev->qdisc_ingress = NULL;
583                 qdisc_destroy(qdisc);
584         }
585 #endif
586         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
587         qdisc_unlock_tree(dev);
588 }
589
590 EXPORT_SYMBOL(__netdev_watchdog_up);
591 EXPORT_SYMBOL(noop_qdisc);
592 EXPORT_SYMBOL(noop_qdisc_ops);
593 EXPORT_SYMBOL(qdisc_create_dflt);
594 EXPORT_SYMBOL(qdisc_destroy);
595 EXPORT_SYMBOL(qdisc_reset);
596 EXPORT_SYMBOL(qdisc_restart);
597 EXPORT_SYMBOL(qdisc_lock_tree);
598 EXPORT_SYMBOL(qdisc_unlock_tree);