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 unsigned lockless; 138 int ret; 139 140 /* Dequeue packet */ 141 if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL)) 142 return 0; 143 144 /* 145 * When the driver has LLTX set, it does its own locking in 146 * start_xmit. These checks are worth it because even uncongested 147 * locks can be quite expensive. The driver can do a trylock, as 148 * is being done here; in case of lock contention it should return 149 * NETDEV_TX_LOCKED and the packet will be requeued. 150 */ 151 lockless = (dev->features & NETIF_F_LLTX); 152 153 if (!lockless && !netif_tx_trylock(dev)) { 154 /* Another CPU grabbed the driver tx lock */ 155 return handle_dev_cpu_collision(skb, dev, q); 156 } 157 158 /* And release queue */ 159 spin_unlock(&dev->queue_lock); 160 161 ret = dev_hard_start_xmit(skb, dev); 162 163 if (!lockless) 164 netif_tx_unlock(dev); 165 166 spin_lock(&dev->queue_lock); 167 q = dev->qdisc; 168 169 switch (ret) { 170 case NETDEV_TX_OK: 171 /* Driver sent out skb successfully */ 172 ret = qdisc_qlen(q); 173 break; 174 175 case NETDEV_TX_LOCKED: 176 /* Driver try lock failed */ 177 ret = handle_dev_cpu_collision(skb, dev, q); 178 break; 179 180 default: 181 /* Driver returned NETDEV_TX_BUSY - requeue skb */ 182 if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit())) 183 printk(KERN_WARNING "BUG %s code %d qlen %d\n", 184 dev->name, ret, q->q.qlen); 185 186 ret = dev_requeue_skb(skb, dev, q); 187 break; 188 } 189 190 return ret; 191 } 192 193 void __qdisc_run(struct net_device *dev) 194 { 195 do { 196 if (!qdisc_restart(dev)) 197 break; 198 } while (!netif_queue_stopped(dev)); 199 200 clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state); 201 } 202 203 static void dev_watchdog(unsigned long arg) 204 { 205 struct net_device *dev = (struct net_device *)arg; 206 207 netif_tx_lock(dev); 208 if (dev->qdisc != &noop_qdisc) { 209 if (netif_device_present(dev) && 210 netif_running(dev) && 211 netif_carrier_ok(dev)) { 212 if (netif_queue_stopped(dev) && 213 time_after(jiffies, dev->trans_start + dev->watchdog_timeo)) { 214 215 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n", 216 dev->name); 217 dev->tx_timeout(dev); 218 } 219 if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo))) 220 dev_hold(dev); 221 } 222 } 223 netif_tx_unlock(dev); 224 225 dev_put(dev); 226 } 227 228 static void dev_watchdog_init(struct net_device *dev) 229 { 230 init_timer(&dev->watchdog_timer); 231 dev->watchdog_timer.data = (unsigned long)dev; 232 dev->watchdog_timer.function = dev_watchdog; 233 } 234 235 void __netdev_watchdog_up(struct net_device *dev) 236 { 237 if (dev->tx_timeout) { 238 if (dev->watchdog_timeo <= 0) 239 dev->watchdog_timeo = 5*HZ; 240 if (!mod_timer(&dev->watchdog_timer, 241 round_jiffies(jiffies + dev->watchdog_timeo))) 242 dev_hold(dev); 243 } 244 } 245 246 static void dev_watchdog_up(struct net_device *dev) 247 { 248 __netdev_watchdog_up(dev); 249 } 250 251 static void dev_watchdog_down(struct net_device *dev) 252 { 253 netif_tx_lock_bh(dev); 254 if (del_timer(&dev->watchdog_timer)) 255 dev_put(dev); 256 netif_tx_unlock_bh(dev); 257 } 258 259 void netif_carrier_on(struct net_device *dev) 260 { 261 if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) 262 linkwatch_fire_event(dev); 263 if (netif_running(dev)) 264 __netdev_watchdog_up(dev); 265 } 266 267 void netif_carrier_off(struct net_device *dev) 268 { 269 if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) 270 linkwatch_fire_event(dev); 271 } 272 273 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces 274 under all circumstances. It is difficult to invent anything faster or 275 cheaper. 276 */ 277 278 static int noop_enqueue(struct sk_buff *skb, struct Qdisc * qdisc) 279 { 280 kfree_skb(skb); 281 return NET_XMIT_CN; 282 } 283 284 static struct sk_buff *noop_dequeue(struct Qdisc * qdisc) 285 { 286 return NULL; 287 } 288 289 static int noop_requeue(struct sk_buff *skb, struct Qdisc* qdisc) 290 { 291 if (net_ratelimit()) 292 printk(KERN_DEBUG "%s deferred output. It is buggy.\n", 293 skb->dev->name); 294 kfree_skb(skb); 295 return NET_XMIT_CN; 296 } 297 298 struct Qdisc_ops noop_qdisc_ops = { 299 .id = "noop", 300 .priv_size = 0, 301 .enqueue = noop_enqueue, 302 .dequeue = noop_dequeue, 303 .requeue = noop_requeue, 304 .owner = THIS_MODULE, 305 }; 306 307 struct Qdisc noop_qdisc = { 308 .enqueue = noop_enqueue, 309 .dequeue = noop_dequeue, 310 .flags = TCQ_F_BUILTIN, 311 .ops = &noop_qdisc_ops, 312 .list = LIST_HEAD_INIT(noop_qdisc.list), 313 }; 314 315 static struct Qdisc_ops noqueue_qdisc_ops = { 316 .id = "noqueue", 317 .priv_size = 0, 318 .enqueue = noop_enqueue, 319 .dequeue = noop_dequeue, 320 .requeue = noop_requeue, 321 .owner = THIS_MODULE, 322 }; 323 324 static struct Qdisc noqueue_qdisc = { 325 .enqueue = NULL, 326 .dequeue = noop_dequeue, 327 .flags = TCQ_F_BUILTIN, 328 .ops = &noqueue_qdisc_ops, 329 .list = LIST_HEAD_INIT(noqueue_qdisc.list), 330 }; 331 332 333 static const u8 prio2band[TC_PRIO_MAX+1] = 334 { 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 }; 335 336 /* 3-band FIFO queue: old style, but should be a bit faster than 337 generic prio+fifo combination. 338 */ 339 340 #define PFIFO_FAST_BANDS 3 341 342 static inline struct sk_buff_head *prio2list(struct sk_buff *skb, 343 struct Qdisc *qdisc) 344 { 345 struct sk_buff_head *list = qdisc_priv(qdisc); 346 return list + prio2band[skb->priority & TC_PRIO_MAX]; 347 } 348 349 static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc) 350 { 351 struct sk_buff_head *list = prio2list(skb, qdisc); 352 353 if (skb_queue_len(list) < qdisc->dev->tx_queue_len) { 354 qdisc->q.qlen++; 355 return __qdisc_enqueue_tail(skb, qdisc, list); 356 } 357 358 return qdisc_drop(skb, qdisc); 359 } 360 361 static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc) 362 { 363 int prio; 364 struct sk_buff_head *list = qdisc_priv(qdisc); 365 366 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) { 367 if (!skb_queue_empty(list + prio)) { 368 qdisc->q.qlen--; 369 return __qdisc_dequeue_head(qdisc, list + prio); 370 } 371 } 372 373 return NULL; 374 } 375 376 static int pfifo_fast_requeue(struct sk_buff *skb, struct Qdisc* qdisc) 377 { 378 qdisc->q.qlen++; 379 return __qdisc_requeue(skb, qdisc, prio2list(skb, qdisc)); 380 } 381 382 static void pfifo_fast_reset(struct Qdisc* qdisc) 383 { 384 int prio; 385 struct sk_buff_head *list = qdisc_priv(qdisc); 386 387 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) 388 __qdisc_reset_queue(qdisc, list + prio); 389 390 qdisc->qstats.backlog = 0; 391 qdisc->q.qlen = 0; 392 } 393 394 static int pfifo_fast_dump(struct Qdisc *qdisc, struct sk_buff *skb) 395 { 396 struct tc_prio_qopt opt = { .bands = PFIFO_FAST_BANDS }; 397 398 memcpy(&opt.priomap, prio2band, TC_PRIO_MAX+1); 399 RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt); 400 return skb->len; 401 402 rtattr_failure: 403 return -1; 404 } 405 406 static int pfifo_fast_init(struct Qdisc *qdisc, struct rtattr *opt) 407 { 408 int prio; 409 struct sk_buff_head *list = qdisc_priv(qdisc); 410 411 for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) 412 skb_queue_head_init(list + prio); 413 414 return 0; 415 } 416 417 static struct Qdisc_ops pfifo_fast_ops = { 418 .id = "pfifo_fast", 419 .priv_size = PFIFO_FAST_BANDS * sizeof(struct sk_buff_head), 420 .enqueue = pfifo_fast_enqueue, 421 .dequeue = pfifo_fast_dequeue, 422 .requeue = pfifo_fast_requeue, 423 .init = pfifo_fast_init, 424 .reset = pfifo_fast_reset, 425 .dump = pfifo_fast_dump, 426 .owner = THIS_MODULE, 427 }; 428 429 struct Qdisc *qdisc_alloc(struct net_device *dev, struct Qdisc_ops *ops) 430 { 431 void *p; 432 struct Qdisc *sch; 433 unsigned int size; 434 int err = -ENOBUFS; 435 436 /* ensure that the Qdisc and the private data are 32-byte aligned */ 437 size = QDISC_ALIGN(sizeof(*sch)); 438 size += ops->priv_size + (QDISC_ALIGNTO - 1); 439 440 p = kzalloc(size, GFP_KERNEL); 441 if (!p) 442 goto errout; 443 sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p); 444 sch->padded = (char *) sch - (char *) p; 445 446 INIT_LIST_HEAD(&sch->list); 447 skb_queue_head_init(&sch->q); 448 sch->ops = ops; 449 sch->enqueue = ops->enqueue; 450 sch->dequeue = ops->dequeue; 451 sch->dev = dev; 452 dev_hold(dev); 453 atomic_set(&sch->refcnt, 1); 454 455 return sch; 456 errout: 457 return ERR_PTR(-err); 458 } 459 460 struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops, 461 unsigned int parentid) 462 { 463 struct Qdisc *sch; 464 465 sch = qdisc_alloc(dev, ops); 466 if (IS_ERR(sch)) 467 goto errout; 468 sch->stats_lock = &dev->queue_lock; 469 sch->parent = parentid; 470 471 if (!ops->init || ops->init(sch, NULL) == 0) 472 return sch; 473 474 qdisc_destroy(sch); 475 errout: 476 return NULL; 477 } 478 479 /* Under dev->queue_lock and BH! */ 480 481 void qdisc_reset(struct Qdisc *qdisc) 482 { 483 struct Qdisc_ops *ops = qdisc->ops; 484 485 if (ops->reset) 486 ops->reset(qdisc); 487 } 488 489 /* this is the rcu callback function to clean up a qdisc when there 490 * are no further references to it */ 491 492 static void __qdisc_destroy(struct rcu_head *head) 493 { 494 struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu); 495 kfree((char *) qdisc - qdisc->padded); 496 } 497 498 /* Under dev->queue_lock and BH! */ 499 500 void qdisc_destroy(struct Qdisc *qdisc) 501 { 502 struct Qdisc_ops *ops = qdisc->ops; 503 504 if (qdisc->flags & TCQ_F_BUILTIN || 505 !atomic_dec_and_test(&qdisc->refcnt)) 506 return; 507 508 list_del(&qdisc->list); 509 gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est); 510 if (ops->reset) 511 ops->reset(qdisc); 512 if (ops->destroy) 513 ops->destroy(qdisc); 514 515 module_put(ops->owner); 516 dev_put(qdisc->dev); 517 call_rcu(&qdisc->q_rcu, __qdisc_destroy); 518 } 519 520 void dev_activate(struct net_device *dev) 521 { 522 /* No queueing discipline is attached to device; 523 create default one i.e. pfifo_fast for devices, 524 which need queueing and noqueue_qdisc for 525 virtual interfaces 526 */ 527 528 if (dev->qdisc_sleeping == &noop_qdisc) { 529 struct Qdisc *qdisc; 530 if (dev->tx_queue_len) { 531 qdisc = qdisc_create_dflt(dev, &pfifo_fast_ops, 532 TC_H_ROOT); 533 if (qdisc == NULL) { 534 printk(KERN_INFO "%s: activation failed\n", dev->name); 535 return; 536 } 537 list_add_tail(&qdisc->list, &dev->qdisc_list); 538 } else { 539 qdisc = &noqueue_qdisc; 540 } 541 dev->qdisc_sleeping = qdisc; 542 } 543 544 if (!netif_carrier_ok(dev)) 545 /* Delay activation until next carrier-on event */ 546 return; 547 548 spin_lock_bh(&dev->queue_lock); 549 rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping); 550 if (dev->qdisc != &noqueue_qdisc) { 551 dev->trans_start = jiffies; 552 dev_watchdog_up(dev); 553 } 554 spin_unlock_bh(&dev->queue_lock); 555 } 556 557 void dev_deactivate(struct net_device *dev) 558 { 559 struct Qdisc *qdisc; 560 struct sk_buff *skb; 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 dev_queue_xmit calls. */ 577 synchronize_rcu(); 578 579 /* Wait for outstanding qdisc_run calls. */ 580 while (test_bit(__LINK_STATE_QDISC_RUNNING, &dev->state)) 581 yield(); 582 } 583 584 void dev_init_scheduler(struct net_device *dev) 585 { 586 qdisc_lock_tree(dev); 587 dev->qdisc = &noop_qdisc; 588 dev->qdisc_sleeping = &noop_qdisc; 589 INIT_LIST_HEAD(&dev->qdisc_list); 590 qdisc_unlock_tree(dev); 591 592 dev_watchdog_init(dev); 593 } 594 595 void dev_shutdown(struct net_device *dev) 596 { 597 struct Qdisc *qdisc; 598 599 qdisc_lock_tree(dev); 600 qdisc = dev->qdisc_sleeping; 601 dev->qdisc = &noop_qdisc; 602 dev->qdisc_sleeping = &noop_qdisc; 603 qdisc_destroy(qdisc); 604 #if defined(CONFIG_NET_SCH_INGRESS) || defined(CONFIG_NET_SCH_INGRESS_MODULE) 605 if ((qdisc = dev->qdisc_ingress) != NULL) { 606 dev->qdisc_ingress = NULL; 607 qdisc_destroy(qdisc); 608 } 609 #endif 610 BUG_TRAP(!timer_pending(&dev->watchdog_timer)); 611 qdisc_unlock_tree(dev); 612 } 613 614 EXPORT_SYMBOL(netif_carrier_on); 615 EXPORT_SYMBOL(netif_carrier_off); 616 EXPORT_SYMBOL(noop_qdisc); 617 EXPORT_SYMBOL(qdisc_create_dflt); 618 EXPORT_SYMBOL(qdisc_destroy); 619 EXPORT_SYMBOL(qdisc_reset); 620 EXPORT_SYMBOL(qdisc_lock_tree); 621 EXPORT_SYMBOL(qdisc_unlock_tree); 622