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   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 {
  44         spin_lock_bh(&dev->queue_lock);
  45         spin_lock(&dev->ingress_lock);
  46 }
  47
  48 void qdisc_unlock_tree(struct net_device *dev)
  49 {
  50         spin_unlock(&dev->ingress_lock);
  51         spin_unlock_bh(&dev->queue_lock);
  52 }
  53
  54 static inline int qdisc_qlen(struct Qdisc *q)
  55 {
  56         return q->q.qlen;
  57 }
  58
  59 static inline int dev_requeue_skb(struct sk_buff *skb, struct net_device *dev,
  60                                   struct Qdisc *q)
  61 {
  62         if (unlikely(skb->next))
  63                 dev->gso_skb = skb;
  64         else
  65                 q->ops->requeue(skb, q);
  66
  67         netif_schedule(dev);
  68         return 0;
  69 }
  70
  71 static inline struct sk_buff *dev_dequeue_skb(struct net_device *dev,
  72                                               struct Qdisc *q)
  73 {
  74         struct sk_buff *skb;
  75
  76         if ((skb = dev->gso_skb))
  77                 dev->gso_skb = NULL;
  78         else
  79                 skb = q->dequeue(q);
  80
  81         return skb;
  82 }
  83
  84 static inline int handle_dev_cpu_collision(struct sk_buff *skb,
  85                                            struct net_device *dev,
  86                                            struct Qdisc *q)
  87 {
  88         int ret;
  89
  90         if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
  91                 /*
  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.
  96                  */
  97                 kfree_skb(skb);
  98                 if (net_ratelimit())
  99                         printk(KERN_WARNING "Dead loop on netdevice %s, "
 100                                "fix it urgently!\n", dev->name);
 101                 ret = qdisc_qlen(q);
 102         } else {
 103                 /*
 104                  * Another cpu is holding lock, requeue & delay xmits for
 105                  * some time.
 106                  */
 107                 __get_cpu_var(netdev_rx_stat).cpu_collision++;
 108                 ret = dev_requeue_skb(skb, dev, q);
 109         }
 110
 111         return ret;
 112 }
 113
 114 /*
 115  * NOTE: Called under dev->queue_lock with locally disabled BH.
 116  *
 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.
 120  *
 121  *  netif_tx_lock serializes accesses to device driver.
 122  *
 123  *  dev->queue_lock and netif_tx_lock are mutually exclusive,
 124  *  if one is grabbed, another must be free.
 125  *
 126  * Note, that this procedure can be called by a watchdog timer
 127  *
 128  * Returns to the caller:
 129  *                              0  - queue is empty or throttled.
 130  *                              >0 - queue is not empty.
 131  *
 132  */
 133 static inline int qdisc_restart(struct net_device *dev)
 134 {
 135         struct Qdisc *q = dev->qdisc;
 136         struct sk_buff *skb;
 137         int ret = NETDEV_TX_BUSY;
 138
 139         /* Dequeue packet */
 140         if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
 141                 return 0;
 142
 143
 144         /* And release queue */
 145         spin_unlock(&dev->queue_lock);
 146
 147         HARD_TX_LOCK(dev, smp_processor_id());
 148         if (!netif_subqueue_stopped(dev, skb))
 149                 ret = dev_hard_start_xmit(skb, dev);
 150         HARD_TX_UNLOCK(dev);
 151
 152         spin_lock(&dev->queue_lock);
 153         q = dev->qdisc;
 154
 155         switch (ret) {
 156         case NETDEV_TX_OK:
 157                 /* Driver sent out skb successfully */
 158                 ret = qdisc_qlen(q);
 159                 break;
 160
 161         case NETDEV_TX_LOCKED:
 162                 /* Driver try lock failed */
 163                 ret = handle_dev_cpu_collision(skb, dev, q);
 164                 break;
 165
 166         default:
 167                 /* Driver returned NETDEV_TX_BUSY - requeue skb */
 168                 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
 169                         printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 170                                dev->name, ret, q->q.qlen);
 171
 172                 ret = dev_requeue_skb(skb, dev, q);
 173                 break;
 174         }
 175
 176         return ret;
 177 }
 178
 179 void __qdisc_run(struct net_device *dev)
 180 {
 181         do {
 182                 if (!qdisc_restart(dev))
 183                         break;
 184         } while (!netif_queue_stopped(dev));
 185
 186         clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
 187 }
 188
 189 static void dev_watchdog(unsigned long arg)
 190 {
 191         struct net_device *dev = (struct net_device *)arg;
 192
 193         netif_tx_lock(dev);
 194         if (dev->qdisc != &noop_qdisc) {
 195                 if (netif_device_present(dev) &&
 196                     netif_running(dev) &&
 197                     netif_carrier_ok(dev)) {
 198                         if (netif_queue_stopped(dev) &&
 199                             time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {
 200
 201                                 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
 202                                        dev->name);
 203                                 dev->tx_timeout(dev);
 204                         }
 205                         if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo)))
 206                                 dev_hold(dev);
 207                 }
 208         }
 209         netif_tx_unlock(dev);
 210
 211         dev_put(dev);
 212 }
 213
 214 static void dev_watchdog_init(struct net_device *dev)
 215 {
 216         init_timer(&dev->watchdog_timer);
 217         dev->watchdog_timer.data = (unsigned long)dev;
 218         dev->watchdog_timer.function = dev_watchdog;
 219 }
 220
 221 void __netdev_watchdog_up(struct net_device *dev)
 222 {
 223         if (dev->tx_timeout) {
 224                 if (dev->watchdog_timeo <= 0)
 225                         dev->watchdog_timeo = 5*HZ;
 226                 if (!mod_timer(&dev->watchdog_timer,
 227                                round_jiffies(jiffies + dev->watchdog_timeo)))
 228                         dev_hold(dev);
 229         }
 230 }
 231
 232 static void dev_watchdog_up(struct net_device *dev)
 233 {
 234         __netdev_watchdog_up(dev);
 235 }
 236
 237 static void dev_watchdog_down(struct net_device *dev)
 238 {
 239         netif_tx_lock_bh(dev);
 240         if (del_timer(&dev->watchdog_timer))
 241                 dev_put(dev);
 242         netif_tx_unlock_bh(dev);
 243 }
 244
 245 /**
 246  *      netif_carrier_on - set carrier
 247  *      @dev: network device
 248  *
 249  * Device has detected that carrier.
 250  */
 251 void netif_carrier_on(struct net_device *dev)
 252 {
 253         if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 254                 linkwatch_fire_event(dev);
 255                 if (netif_running(dev))
 256                         __netdev_watchdog_up(dev);
 257         }
 258 }
 259
 260 /**
 261  *      netif_carrier_off - clear carrier
 262  *      @dev: network device
 263  *
 264  * Device has detected loss of carrier.
 265  */
 266 void netif_carrier_off(struct net_device *dev)
 267 {
 268         if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
 269                 linkwatch_fire_event(dev);
 270 }
 271
 272 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
 273    under all circumstances. It is difficult to invent anything faster or
 274    cheaper.
 275  */
 276
 277 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
 278 {
 279         kfree_skb(skb);
 280         return NET_XMIT_CN;
 281 }
 282
 283 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
 284 {
 285         return NULL;
 286 }
 287
 288 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 289 {
 290         if (net_ratelimit())
 291                 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
 292                        skb->dev->name);
 293         kfree_skb(skb);
 294         return NET_XMIT_CN;
 295 }
 296
 297 struct Qdisc_ops noop_qdisc_ops = {
 298         .id             =       "noop",
 299         .priv_size      =       0,
 300         .enqueue        =       noop_enqueue,
 301         .dequeue        =       noop_dequeue,
 302         .requeue        =       noop_requeue,
 303         .owner          =       THIS_MODULE,
 304 };
 305
 306 struct Qdisc noop_qdisc = {
 307         .enqueue        =       noop_enqueue,
 308         .dequeue        =       noop_dequeue,
 309         .flags          =       TCQ_F_BUILTIN,
 310         .ops            =       &noop_qdisc_ops,
 311         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
 312 };
 313
 314 static struct Qdisc_ops noqueue_qdisc_ops = {
 315         .id             =       "noqueue",
 316         .priv_size      =       0,
 317         .enqueue        =       noop_enqueue,
 318         .dequeue        =       noop_dequeue,
 319         .requeue        =       noop_requeue,
 320         .owner          =       THIS_MODULE,
 321 };
 322
 323 static struct Qdisc noqueue_qdisc = {
 324         .enqueue        =       NULL,
 325         .dequeue        =       noop_dequeue,
 326         .flags          =       TCQ_F_BUILTIN,
 327         .ops            =       &noqueue_qdisc_ops,
 328         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
 329 };
 330
 331
 332 static const u8 prio2band[TC_PRIO_MAX+1] =
 333         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
 334
 335 /* 3-band FIFO queue: old style, but should be a bit faster than
 336    generic prio+fifo combination.
 337  */
 338
 339 #define PFIFO_FAST_BANDS 3
 340
 341 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
 342                                              struct Qdisc *qdisc)
 343 {
 344         struct sk_buff_head *list = qdisc_priv(qdisc);
 345         return list + prio2band[skb->priority & TC_PRIO_MAX];
 346 }
 347
 348 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 349 {
 350         struct sk_buff_head *list = prio2list(skb, qdisc);
 351
 352         if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
 353                 qdisc->q.qlen++;
 354                 return __qdisc_enqueue_tail(skb, qdisc, list);
 355         }
 356
 357         return qdisc_drop(skb, qdisc);
 358 }
 359
 360 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
 361 {
 362         int prio;
 363         struct sk_buff_head *list = qdisc_priv(qdisc);
 364
 365         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
 366                 if (!skb_queue_empty(list + prio)) {
 367                         qdisc->q.qlen--;
 368                         return __qdisc_dequeue_head(qdisc, list + prio);
 369                 }
 370         }
 371
 372         return NULL;
 373 }
 374
 375 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 376 {
 377         qdisc->q.qlen++;
 378         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
 379 }
 380
 381 static void pfifo_fast_reset(struct Qdisc* qdisc)
 382 {
 383         int prio;
 384         struct sk_buff_head *list = qdisc_priv(qdisc);
 385
 386         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 387                 __qdisc_reset_queue(qdisc, list + prio);
 388
 389         qdisc->qstats.backlog = 0;
 390         qdisc->q.qlen = 0;
 391 }
 392
 393 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
 394 {
 395         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
 396
 397         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
 398         RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 399         return skb->len;
 400
 401 rtattr_failure:
 402         return -1;
 403 }
 404
 405 static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
 406 {
 407         int prio;
 408         struct sk_buff_head *list = qdisc_priv(qdisc);
 409
 410         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 411                 skb_queue_head_init(list + prio);
 412
 413         return 0;
 414 }
 415
 416 static struct Qdisc_ops pfifo_fast_ops = {
 417         .id             =       "pfifo_fast",
 418         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
 419         .enqueue        =       pfifo_fast_enqueue,
 420         .dequeue        =       pfifo_fast_dequeue,
 421         .requeue        =       pfifo_fast_requeue,
 422         .init           =       pfifo_fast_init,
 423         .reset          =       pfifo_fast_reset,
 424         .dump           =       pfifo_fast_dump,
 425         .owner          =       THIS_MODULE,
 426 };
 427
 428 struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops)
 429 {
 430         void *p;
 431         struct Qdisc *sch;
 432         unsigned int size;
 433         int err = -ENOBUFS;
 434
 435         /* ensure that the Qdisc and the private data are 32-byte aligned */
 436         size = QDISC_ALIGN(sizeof(*sch));
 437         size += ops->priv_size + (QDISC_ALIGNTO - 1);
 438
 439         p = kzalloc(size, GFP_KERNEL);
 440         if (!p)
 441                 goto errout;
 442         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
 443         sch->padded = (char *) sch - (char *) p;
 444
 445         INIT_LIST_HEAD(&sch->list);
 446         skb_queue_head_init(&sch->q);
 447         sch->ops = ops;
 448         sch->enqueue = ops->enqueue;
 449         sch->dequeue = ops->dequeue;
 450         sch->dev = dev;
 451         dev_hold(dev);
 452         atomic_set(&sch->refcnt, 1);
 453
 454         return sch;
 455 errout:
 456         return ERR_PTR(-err);
 457 }
 458
 459 struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops,
 460                                  unsigned int parentid)
 461 {
 462         struct Qdisc *sch;
 463
 464         sch = qdisc_alloc(dev, ops);
 465         if (IS_ERR(sch))
 466                 goto errout;
 467         sch->stats_lock = &dev->queue_lock;
 468         sch->parent = parentid;
 469
 470         if (!ops->init || ops->init(sch, NULL) == 0)
 471                 return sch;
 472
 473         qdisc_destroy(sch);
 474 errout:
 475         return NULL;
 476 }
 477
 478 /* Under dev->queue_lock and BH! */
 479
 480 void qdisc_reset(struct Qdisc *qdisc)
 481 {
 482         struct Qdisc_ops *ops = qdisc->ops;
 483
 484         if (ops->reset)
 485                 ops->reset(qdisc);
 486 }
 487
 488 /* this is the rcu callback function to clean up a qdisc when there
 489  * are no further references to it */
 490
 491 static void __qdisc_destroy(struct rcu_head *head)
 492 {
 493         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
 494         kfree((char *) qdisc - qdisc->padded);
 495 }
 496
 497 /* Under dev->queue_lock and BH! */
 498
 499 void qdisc_destroy(struct Qdisc *qdisc)
 500 {
 501         struct Qdisc_ops  *ops = qdisc->ops;
 502
 503         if (qdisc->flags & TCQ_F_BUILTIN ||
 504             !atomic_dec_and_test(&qdisc->refcnt))
 505                 return;
 506
 507         list_del(&qdisc->list);
 508         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
 509         if (ops->reset)
 510                 ops->reset(qdisc);
 511         if (ops->destroy)
 512                 ops->destroy(qdisc);
 513
 514         module_put(ops->owner);
 515         dev_put(qdisc->dev);
 516         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
 517 }
 518
 519 void dev_activate(struct net_device *dev)
 520 {
 521         /* No queueing discipline is attached to device;
 522            create default one i.e. pfifo_fast for devices,
 523            which need queueing and noqueue_qdisc for
 524            virtual interfaces
 525          */
 526
 527         if (dev->qdisc_sleeping == &noop_qdisc) {
 528                 struct Qdisc *qdisc;
 529                 if (dev->tx_queue_len) {
 530                         qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops,
 531                                                   TC_H_ROOT);
 532                         if (qdisc == NULL) {
 533                                 printk(KERN_INFO "%s: activation failed\n", dev->name);
 534                                 return;
 535                         }
 536                         list_add_tail(&qdisc->list, &dev->qdisc_list);
 537                 } else {
 538                         qdisc =  &noqueue_qdisc;
 539                 }
 540                 dev->qdisc_sleeping = qdisc;
 541         }
 542
 543         if (!netif_carrier_ok(dev))
 544                 /* Delay activation until next carrier-on event */
 545                 return;
 546
 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);
 552         }
 553         spin_unlock_bh(&dev->queue_lock);
 554 }
 555
 556 void dev_deactivate(struct net_device *dev)
 557 {
 558         struct Qdisc *qdisc;
 559         struct sk_buff *skb;
 560         int running;
 561
 562         spin_lock_bh(&dev->queue_lock);
 563         qdisc = dev->qdisc;
 564         dev->qdisc = &noop_qdisc;
 565
 566         qdisc_reset(qdisc);
 567
 568         skb = dev->gso_skb;
 569         dev->gso_skb = NULL;
 570         spin_unlock_bh(&dev->queue_lock);
 571
 572         kfree_skb(skb);
 573
 574         dev_watchdog_down(dev);
 575
 576         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
 577         synchronize_rcu();
 578
 579         /* Wait for outstanding qdisc_run calls. */
 580         do {
 581                 while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
 582                         yield();
 583
 584                 /*
 585                  * Double-check inside queue lock to ensure that all effects
 586                  * of the queue run are visible when we return.
 587                  */
 588                 spin_lock_bh(&dev->queue_lock);
 589                 running = test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
 590                 spin_unlock_bh(&dev->queue_lock);
 591
 592                 /*
 593                  * The running flag should never be set at this point because
 594                  * we've already set dev->qdisc to noop_qdisc *inside* the same
 595                  * pair of spin locks.  That is, if any qdisc_run starts after
 596                  * our initial test it should see the noop_qdisc and then
 597                  * clear the RUNNING bit before dropping the queue lock.  So
 598                  * if it is set here then we've found a bug.
 599                  */
 600         } while (WARN_ON_ONCE(running));
 601 }
 602
 603 void dev_init_scheduler(struct net_device *dev)
 604 {
 605         qdisc_lock_tree(dev);
 606         dev->qdisc = &noop_qdisc;
 607         dev->qdisc_sleeping = &noop_qdisc;
 608         INIT_LIST_HEAD(&dev->qdisc_list);
 609         qdisc_unlock_tree(dev);
 610
 611         dev_watchdog_init(dev);
 612 }
 613
 614 void dev_shutdown(struct net_device *dev)
 615 {
 616         struct Qdisc *qdisc;
 617
 618         qdisc_lock_tree(dev);
 619         qdisc = dev->qdisc_sleeping;
 620         dev->qdisc = &noop_qdisc;
 621         dev->qdisc_sleeping = &noop_qdisc;
 622         qdisc_destroy(qdisc);
 623 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
 624         if ((qdisc = dev->qdisc_ingress) != NULL) {
 625                 dev->qdisc_ingress = NULL;
 626                 qdisc_destroy(qdisc);
 627         }
 628 #endif
 629         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
 630         qdisc_unlock_tree(dev);
 631 }
 632
 633 EXPORT_SYMBOL(netif_carrier_on);
 634 EXPORT_SYMBOL(netif_carrier_off);
 635 EXPORT_SYMBOL(noop_qdisc);
 636 EXPORT_SYMBOL(qdisc_create_dflt);
 637 EXPORT_SYMBOL(qdisc_destroy);
 638 EXPORT_SYMBOL(qdisc_reset);
 639 EXPORT_SYMBOL(qdisc_lock_tree);
 640 EXPORT_SYMBOL(qdisc_unlock_tree);