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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;
 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         ret = dev_hard_start_xmit(skb, dev);
 149         HARD_TX_UNLOCK(dev);
 150
 151         spin_lock(&dev->queue_lock);
 152         q = dev->qdisc;
 153
 154         switch (ret) {
 155         case NETDEV_TX_OK:
 156                 /* Driver sent out skb successfully */
 157                 ret = qdisc_qlen(q);
 158                 break;
 159
 160         case NETDEV_TX_LOCKED:
 161                 /* Driver try lock failed */
 162                 ret = handle_dev_cpu_collision(skb, dev, q);
 163                 break;
 164
 165         default:
 166                 /* Driver returned NETDEV_TX_BUSY - requeue skb */
 167                 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
 168                         printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 169                                dev->name, ret, q->q.qlen);
 170
 171                 ret = dev_requeue_skb(skb, dev, q);
 172                 break;
 173         }
 174
 175         return ret;
 176 }
 177
 178 void __qdisc_run(struct net_device *dev)
 179 {
 180         do {
 181                 if (!qdisc_restart(dev))
 182                         break;
 183         } while (!netif_queue_stopped(dev));
 184
 185         clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
 186 }
 187
 188 static void dev_watchdog(unsigned long arg)
 189 {
 190         struct net_device *dev = (struct net_device *)arg;
 191
 192         netif_tx_lock(dev);
 193         if (dev->qdisc != &noop_qdisc) {
 194                 if (netif_device_present(dev) &&
 195                     netif_running(dev) &&
 196                     netif_carrier_ok(dev)) {
 197                         if (netif_queue_stopped(dev) &&
 198                             time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) {
 199
 200                                 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
 201                                        dev->name);
 202                                 dev->tx_timeout(dev);
 203                         }
 204                         if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo)))
 205                                 dev_hold(dev);
 206                 }
 207         }
 208         netif_tx_unlock(dev);
 209
 210         dev_put(dev);
 211 }
 212
 213 static void dev_watchdog_init(struct net_device *dev)
 214 {
 215         init_timer(&dev->watchdog_timer);
 216         dev->watchdog_timer.data = (unsigned long)dev;
 217         dev->watchdog_timer.function = dev_watchdog;
 218 }
 219
 220 void __netdev_watchdog_up(struct net_device *dev)
 221 {
 222         if (dev->tx_timeout) {
 223                 if (dev->watchdog_timeo <= 0)
 224                         dev->watchdog_timeo = 5*HZ;
 225                 if (!mod_timer(&dev->watchdog_timer,
 226                                round_jiffies(jiffies + dev->watchdog_timeo)))
 227                         dev_hold(dev);
 228         }
 229 }
 230
 231 static void dev_watchdog_up(struct net_device *dev)
 232 {
 233         __netdev_watchdog_up(dev);
 234 }
 235
 236 static void dev_watchdog_down(struct net_device *dev)
 237 {
 238         netif_tx_lock_bh(dev);
 239         if (del_timer(&dev->watchdog_timer))
 240                 dev_put(dev);
 241         netif_tx_unlock_bh(dev);
 242 }
 243
 244 /**
 245  *      netif_carrier_on - set carrier
 246  *      @dev: network device
 247  *
 248  * Device has detected that carrier.
 249  */
 250 void netif_carrier_on(struct net_device *dev)
 251 {
 252         if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 253                 linkwatch_fire_event(dev);
 254                 if (netif_running(dev))
 255                         __netdev_watchdog_up(dev);
 256         }
 257 }
 258
 259 /**
 260  *      netif_carrier_off - clear carrier
 261  *      @dev: network device
 262  *
 263  * Device has detected loss of carrier.
 264  */
 265 void netif_carrier_off(struct net_device *dev)
 266 {
 267         if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state))
 268                 linkwatch_fire_event(dev);
 269 }
 270
 271 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
 272    under all circumstances. It is difficult to invent anything faster or
 273    cheaper.
 274  */
 275
 276 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc)
 277 {
 278         kfree_skb(skb);
 279         return NET_XMIT_CN;
 280 }
 281
 282 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc)
 283 {
 284         return NULL;
 285 }
 286
 287 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 288 {
 289         if (net_ratelimit())
 290                 printk(KERN_DEBUG "%s deferred output. It is buggy.\n",
 291                        skb->dev->name);
 292         kfree_skb(skb);
 293         return NET_XMIT_CN;
 294 }
 295
 296 struct Qdisc_ops noop_qdisc_ops = {
 297         .id             =       "noop",
 298         .priv_size      =       0,
 299         .enqueue        =       noop_enqueue,
 300         .dequeue        =       noop_dequeue,
 301         .requeue        =       noop_requeue,
 302         .owner          =       THIS_MODULE,
 303 };
 304
 305 struct Qdisc noop_qdisc = {
 306         .enqueue        =       noop_enqueue,
 307         .dequeue        =       noop_dequeue,
 308         .flags          =       TCQ_F_BUILTIN,
 309         .ops            =       &noop_qdisc_ops,
 310         .list           =       LIST_HEAD_INIT(noop_qdisc.list),
 311 };
 312
 313 static struct Qdisc_ops noqueue_qdisc_ops = {
 314         .id             =       "noqueue",
 315         .priv_size      =       0,
 316         .enqueue        =       noop_enqueue,
 317         .dequeue        =       noop_dequeue,
 318         .requeue        =       noop_requeue,
 319         .owner          =       THIS_MODULE,
 320 };
 321
 322 static struct Qdisc noqueue_qdisc = {
 323         .enqueue        =       NULL,
 324         .dequeue        =       noop_dequeue,
 325         .flags          =       TCQ_F_BUILTIN,
 326         .ops            =       &noqueue_qdisc_ops,
 327         .list           =       LIST_HEAD_INIT(noqueue_qdisc.list),
 328 };
 329
 330
 331 static const u8 prio2band[TC_PRIO_MAX+1] =
 332         { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 };
 333
 334 /* 3-band FIFO queue: old style, but should be a bit faster than
 335    generic prio+fifo combination.
 336  */
 337
 338 #define PFIFO_FAST_BANDS 3
 339
 340 static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
 341                                              struct Qdisc *qdisc)
 342 {
 343         struct sk_buff_head *list = qdisc_priv(qdisc);
 344         return list + prio2band[skb->priority & TC_PRIO_MAX];
 345 }
 346
 347 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
 348 {
 349         struct sk_buff_head *list = prio2list(skb, qdisc);
 350
 351         if (skb_queue_len(list) < qdisc->dev->tx_queue_len) {
 352                 qdisc->q.qlen++;
 353                 return __qdisc_enqueue_tail(skb, qdisc, list);
 354         }
 355
 356         return qdisc_drop(skb, qdisc);
 357 }
 358
 359 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
 360 {
 361         int prio;
 362         struct sk_buff_head *list = qdisc_priv(qdisc);
 363
 364         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
 365                 if (!skb_queue_empty(list + prio)) {
 366                         qdisc->q.qlen--;
 367                         return __qdisc_dequeue_head(qdisc, list + prio);
 368                 }
 369         }
 370
 371         return NULL;
 372 }
 373
 374 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc)
 375 {
 376         qdisc->q.qlen++;
 377         return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc));
 378 }
 379
 380 static void pfifo_fast_reset(struct Qdisc* qdisc)
 381 {
 382         int prio;
 383         struct sk_buff_head *list = qdisc_priv(qdisc);
 384
 385         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 386                 __qdisc_reset_queue(qdisc, list + prio);
 387
 388         qdisc->qstats.backlog = 0;
 389         qdisc->q.qlen = 0;
 390 }
 391
 392 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb)
 393 {
 394         struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS };
 395
 396         memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1);
 397         RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 398         return skb->len;
 399
 400 rtattr_failure:
 401         return -1;
 402 }
 403
 404 static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt)
 405 {
 406         int prio;
 407         struct sk_buff_head *list = qdisc_priv(qdisc);
 408
 409         for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
 410                 skb_queue_head_init(list + prio);
 411
 412         return 0;
 413 }
 414
 415 static struct Qdisc_ops pfifo_fast_ops = {
 416         .id             =       "pfifo_fast",
 417         .priv_size      =       PFIFO_FAST_BANDS * sizeof(struct sk_buff_head),
 418         .enqueue        =       pfifo_fast_enqueue,
 419         .dequeue        =       pfifo_fast_dequeue,
 420         .requeue        =       pfifo_fast_requeue,
 421         .init           =       pfifo_fast_init,
 422         .reset          =       pfifo_fast_reset,
 423         .dump           =       pfifo_fast_dump,
 424         .owner          =       THIS_MODULE,
 425 };
 426
 427 struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops)
 428 {
 429         void *p;
 430         struct Qdisc *sch;
 431         unsigned int size;
 432         int err = -ENOBUFS;
 433
 434         /* ensure that the Qdisc and the private data are 32-byte aligned */
 435         size = QDISC_ALIGN(sizeof(*sch));
 436         size += ops->priv_size + (QDISC_ALIGNTO - 1);
 437
 438         p = kzalloc(size, GFP_KERNEL);
 439         if (!p)
 440                 goto errout;
 441         sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
 442         sch->padded = (char *) sch - (char *) p;
 443
 444         INIT_LIST_HEAD(&sch->list);
 445         skb_queue_head_init(&sch->q);
 446         sch->ops = ops;
 447         sch->enqueue = ops->enqueue;
 448         sch->dequeue = ops->dequeue;
 449         sch->dev = dev;
 450         dev_hold(dev);
 451         atomic_set(&sch->refcnt, 1);
 452
 453         return sch;
 454 errout:
 455         return ERR_PTR(-err);
 456 }
 457
 458 struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops,
 459                                  unsigned int parentid)
 460 {
 461         struct Qdisc *sch;
 462
 463         sch = qdisc_alloc(dev, ops);
 464         if (IS_ERR(sch))
 465                 goto errout;
 466         sch->stats_lock = &dev->queue_lock;
 467         sch->parent = parentid;
 468
 469         if (!ops->init || ops->init(sch, NULL) == 0)
 470                 return sch;
 471
 472         qdisc_destroy(sch);
 473 errout:
 474         return NULL;
 475 }
 476
 477 /* Under dev->queue_lock and BH! */
 478
 479 void qdisc_reset(struct Qdisc *qdisc)
 480 {
 481         struct Qdisc_ops *ops = qdisc->ops;
 482
 483         if (ops->reset)
 484                 ops->reset(qdisc);
 485 }
 486
 487 /* this is the rcu callback function to clean up a qdisc when there
 488  * are no further references to it */
 489
 490 static void __qdisc_destroy(struct rcu_head *head)
 491 {
 492         struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
 493         kfree((char *) qdisc - qdisc->padded);
 494 }
 495
 496 /* Under dev->queue_lock and BH! */
 497
 498 void qdisc_destroy(struct Qdisc *qdisc)
 499 {
 500         struct Qdisc_ops  *ops = qdisc->ops;
 501
 502         if (qdisc->flags & TCQ_F_BUILTIN ||
 503             !atomic_dec_and_test(&qdisc->refcnt))
 504                 return;
 505
 506         list_del(&qdisc->list);
 507         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
 508         if (ops->reset)
 509                 ops->reset(qdisc);
 510         if (ops->destroy)
 511                 ops->destroy(qdisc);
 512
 513         module_put(ops->owner);
 514         dev_put(qdisc->dev);
 515         call_rcu(&qdisc->q_rcu, __qdisc_destroy);
 516 }
 517
 518 void dev_activate(struct net_device *dev)
 519 {
 520         /* No queueing discipline is attached to device;
 521            create default one i.e. pfifo_fast for devices,
 522            which need queueing and noqueue_qdisc for
 523            virtual interfaces
 524          */
 525
 526         if (dev->qdisc_sleeping == &noop_qdisc) {
 527                 struct Qdisc *qdisc;
 528                 if (dev->tx_queue_len) {
 529                         qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops,
 530                                                   TC_H_ROOT);
 531                         if (qdisc == NULL) {
 532                                 printk(KERN_INFO "%s: activation failed\n", dev->name);
 533                                 return;
 534                         }
 535                         list_add_tail(&qdisc->list, &dev->qdisc_list);
 536                 } else {
 537                         qdisc =  &noqueue_qdisc;
 538                 }
 539                 dev->qdisc_sleeping = qdisc;
 540         }
 541
 542         if (!netif_carrier_ok(dev))
 543                 /* Delay activation until next carrier-on event */
 544                 return;
 545
 546         spin_lock_bh(&dev->queue_lock);
 547         rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping);
 548         if (dev->qdisc != &noqueue_qdisc) {
 549                 dev->trans_start = jiffies;
 550                 dev_watchdog_up(dev);
 551         }
 552         spin_unlock_bh(&dev->queue_lock);
 553 }
 554
 555 void dev_deactivate(struct net_device *dev)
 556 {
 557         struct Qdisc *qdisc;
 558         struct sk_buff *skb;
 559         int running;
 560
 561         spin_lock_bh(&dev->queue_lock);
 562         qdisc = dev->qdisc;
 563         dev->qdisc = &noop_qdisc;
 564
 565         qdisc_reset(qdisc);
 566
 567         skb = dev->gso_skb;
 568         dev->gso_skb = NULL;
 569         spin_unlock_bh(&dev->queue_lock);
 570
 571         kfree_skb(skb);
 572
 573         dev_watchdog_down(dev);
 574
 575         /* Wait for outstanding qdisc-less dev_queue_xmit calls. */
 576         synchronize_rcu();
 577
 578         /* Wait for outstanding qdisc_run calls. */
 579         do {
 580                 while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
 581                         yield();
 582
 583                 /*
 584                  * Double-check inside queue lock to ensure that all effects
 585                  * of the queue run are visible when we return.
 586                  */
 587                 spin_lock_bh(&dev->queue_lock);
 588                 running = test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
 589                 spin_unlock_bh(&dev->queue_lock);
 590
 591                 /*
 592                  * The running flag should never be set at this point because
 593                  * we've already set dev->qdisc to noop_qdisc *inside* the same
 594                  * pair of spin locks.  That is, if any qdisc_run starts after
 595                  * our initial test it should see the noop_qdisc and then
 596                  * clear the RUNNING bit before dropping the queue lock.  So
 597                  * if it is set here then we've found a bug.
 598                  */
 599         } while (WARN_ON_ONCE(running));
 600 }
 601
 602 void dev_init_scheduler(struct net_device *dev)
 603 {
 604         qdisc_lock_tree(dev);
 605         dev->qdisc = &noop_qdisc;
 606         dev->qdisc_sleeping = &noop_qdisc;
 607         INIT_LIST_HEAD(&dev->qdisc_list);
 608         qdisc_unlock_tree(dev);
 609
 610         dev_watchdog_init(dev);
 611 }
 612
 613 void dev_shutdown(struct net_device *dev)
 614 {
 615         struct Qdisc *qdisc;
 616
 617         qdisc_lock_tree(dev);
 618         qdisc = dev->qdisc_sleeping;
 619         dev->qdisc = &noop_qdisc;
 620         dev->qdisc_sleeping = &noop_qdisc;
 621         qdisc_destroy(qdisc);
 622 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE)
 623         if ((qdisc = dev->qdisc_ingress) != NULL) {
 624                 dev->qdisc_ingress = NULL;
 625                 qdisc_destroy(qdisc);
 626         }
 627 #endif
 628         BUG_TRAP(!timer_pending(&dev->watchdog_timer));
 629         qdisc_unlock_tree(dev);
 630 }
 631
 632 EXPORT_SYMBOL(netif_carrier_on);
 633 EXPORT_SYMBOL(netif_carrier_off);
 634 EXPORT_SYMBOL(noop_qdisc);
 635 EXPORT_SYMBOL(qdisc_create_dflt);
 636 EXPORT_SYMBOL(qdisc_destroy);
 637 EXPORT_SYMBOL(qdisc_reset);
 638 EXPORT_SYMBOL(qdisc_lock_tree);
 639 EXPORT_SYMBOL(qdisc_unlock_tree);