1/* 2 * linux/kernel/softirq.c 3 * 4 * Copyright (C) 1992 Linus Torvalds 5 * 6 * Distribute under GPLv2. 7 * 8 * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) 9 */ 10 11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 12 13#include <linux/export.h> 14#include <linux/kernel_stat.h> 15#include <linux/interrupt.h> 16#include <linux/init.h> 17#include <linux/mm.h> 18#include <linux/notifier.h> 19#include <linux/percpu.h> 20#include <linux/cpu.h> 21#include <linux/freezer.h> 22#include <linux/kthread.h> 23#include <linux/rcupdate.h> 24#include <linux/ftrace.h> 25#include <linux/smp.h> 26#include <linux/smpboot.h> 27#include <linux/tick.h> 28#include <linux/irq.h> 29 30#define CREATE_TRACE_POINTS 31#include <trace/events/irq.h> 32 33/* 34 - No shared variables, all the data are CPU local. 35 - If a softirq needs serialization, let it serialize itself 36 by its own spinlocks. 37 - Even if softirq is serialized, only local cpu is marked for 38 execution. Hence, we get something sort of weak cpu binding. 39 Though it is still not clear, will it result in better locality 40 or will not. 41 42 Examples: 43 - NET RX softirq. It is multithreaded and does not require 44 any global serialization. 45 - NET TX softirq. It kicks software netdevice queues, hence 46 it is logically serialized per device, but this serialization 47 is invisible to common code. 48 - Tasklets: serialized wrt itself. 49 */ 50 51#ifndef __ARCH_IRQ_STAT 52irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned; 53EXPORT_SYMBOL(irq_stat); 54#endif 55 56static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; 57 58DEFINE_PER_CPU(struct task_struct *, ksoftirqd); 59 60const char * const softirq_to_name[NR_SOFTIRQS] = { 61 "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL", 62 "TASKLET", "SCHED", "HRTIMER", "RCU" 63}; 64 65/* 66 * we cannot loop indefinitely here to avoid userspace starvation, 67 * but we also don't want to introduce a worst case 1/HZ latency 68 * to the pending events, so lets the scheduler to balance 69 * the softirq load for us. 70 */ 71static void wakeup_softirqd(void) 72{ 73 /* Interrupts are disabled: no need to stop preemption */ 74 struct task_struct *tsk = __this_cpu_read(ksoftirqd); 75 76 if (tsk && tsk->state != TASK_RUNNING) 77 wake_up_process(tsk); 78} 79 80/* 81 * preempt_count and SOFTIRQ_OFFSET usage: 82 * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving 83 * softirq processing. 84 * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) 85 * on local_bh_disable or local_bh_enable. 86 * This lets us distinguish between whether we are currently processing 87 * softirq and whether we just have bh disabled. 88 */ 89 90/* 91 * This one is for softirq.c-internal use, 92 * where hardirqs are disabled legitimately: 93 */ 94#ifdef CONFIG_TRACE_IRQFLAGS 95void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) 96{ 97 unsigned long flags; 98 99 WARN_ON_ONCE(in_irq()); 100 101 raw_local_irq_save(flags); 102 /* 103 * The preempt tracer hooks into preempt_count_add and will break 104 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET 105 * is set and before current->softirq_enabled is cleared. 106 * We must manually increment preempt_count here and manually 107 * call the trace_preempt_off later. 108 */ 109 __preempt_count_add(cnt); 110 /* 111 * Were softirqs turned off above: 112 */ 113 if (softirq_count() == (cnt & SOFTIRQ_MASK)) 114 trace_softirqs_off(ip); 115 raw_local_irq_restore(flags); 116 117 if (preempt_count() == cnt) { 118#ifdef CONFIG_DEBUG_PREEMPT 119 current->preempt_disable_ip = get_parent_ip(CALLER_ADDR1); 120#endif 121 trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); 122 } 123} 124EXPORT_SYMBOL(__local_bh_disable_ip); 125#endif /* CONFIG_TRACE_IRQFLAGS */ 126 127static void __local_bh_enable(unsigned int cnt) 128{ 129 WARN_ON_ONCE(!irqs_disabled()); 130 131 if (softirq_count() == (cnt & SOFTIRQ_MASK)) 132 trace_softirqs_on(_RET_IP_); 133 preempt_count_sub(cnt); 134} 135 136/* 137 * Special-case - softirqs can safely be enabled in 138 * cond_resched_softirq(), or by __do_softirq(), 139 * without processing still-pending softirqs: 140 */ 141void _local_bh_enable(void) 142{ 143 WARN_ON_ONCE(in_irq()); 144 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); 145} 146EXPORT_SYMBOL(_local_bh_enable); 147 148void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) 149{ 150 WARN_ON_ONCE(in_irq() || irqs_disabled()); 151#ifdef CONFIG_TRACE_IRQFLAGS 152 local_irq_disable(); 153#endif 154 /* 155 * Are softirqs going to be turned on now: 156 */ 157 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) 158 trace_softirqs_on(ip); 159 /* 160 * Keep preemption disabled until we are done with 161 * softirq processing: 162 */ 163 preempt_count_sub(cnt - 1); 164 165 if (unlikely(!in_interrupt() && local_softirq_pending())) { 166 /* 167 * Run softirq if any pending. And do it in its own stack 168 * as we may be calling this deep in a task call stack already. 169 */ 170 do_softirq(); 171 } 172 173 preempt_count_dec(); 174#ifdef CONFIG_TRACE_IRQFLAGS 175 local_irq_enable(); 176#endif 177 preempt_check_resched(); 178} 179EXPORT_SYMBOL(__local_bh_enable_ip); 180 181/* 182 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, 183 * but break the loop if need_resched() is set or after 2 ms. 184 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in 185 * certain cases, such as stop_machine(), jiffies may cease to 186 * increment and so we need the MAX_SOFTIRQ_RESTART limit as 187 * well to make sure we eventually return from this method. 188 * 189 * These limits have been established via experimentation. 190 * The two things to balance is latency against fairness - 191 * we want to handle softirqs as soon as possible, but they 192 * should not be able to lock up the box. 193 */ 194#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) 195#define MAX_SOFTIRQ_RESTART 10 196 197#ifdef CONFIG_TRACE_IRQFLAGS 198/* 199 * When we run softirqs from irq_exit() and thus on the hardirq stack we need 200 * to keep the lockdep irq context tracking as tight as possible in order to 201 * not miss-qualify lock contexts and miss possible deadlocks. 202 */ 203 204static inline bool lockdep_softirq_start(void) 205{ 206 bool in_hardirq = false; 207 208 if (trace_hardirq_context(current)) { 209 in_hardirq = true; 210 trace_hardirq_exit(); 211 } 212 213 lockdep_softirq_enter(); 214 215 return in_hardirq; 216} 217 218static inline void lockdep_softirq_end(bool in_hardirq) 219{ 220 lockdep_softirq_exit(); 221 222 if (in_hardirq) 223 trace_hardirq_enter(); 224} 225#else 226static inline bool lockdep_softirq_start(void) { return false; } 227static inline void lockdep_softirq_end(bool in_hardirq) { } 228#endif 229 230asmlinkage __visible void __do_softirq(void) 231{ 232 unsigned long end = jiffies + MAX_SOFTIRQ_TIME; 233 unsigned long old_flags = current->flags; 234 int max_restart = MAX_SOFTIRQ_RESTART; 235 struct softirq_action *h; 236 bool in_hardirq; 237 __u32 pending; 238 int softirq_bit; 239 240 /* 241 * Mask out PF_MEMALLOC s current task context is borrowed for the 242 * softirq. A softirq handled such as network RX might set PF_MEMALLOC 243 * again if the socket is related to swap 244 */ 245 current->flags &= ~PF_MEMALLOC; 246 247 pending = local_softirq_pending(); 248 account_irq_enter_time(current); 249 250 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); 251 in_hardirq = lockdep_softirq_start(); 252 253restart: 254 /* Reset the pending bitmask before enabling irqs */ 255 set_softirq_pending(0); 256 257 local_irq_enable(); 258 259 h = softirq_vec; 260 261 while ((softirq_bit = ffs(pending))) { 262 unsigned int vec_nr; 263 int prev_count; 264 265 h += softirq_bit - 1; 266 267 vec_nr = h - softirq_vec; 268 prev_count = preempt_count(); 269 270 kstat_incr_softirqs_this_cpu(vec_nr); 271 272 trace_softirq_entry(vec_nr); 273 h->action(h); 274 trace_softirq_exit(vec_nr); 275 if (unlikely(prev_count != preempt_count())) { 276 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n", 277 vec_nr, softirq_to_name[vec_nr], h->action, 278 prev_count, preempt_count()); 279 preempt_count_set(prev_count); 280 } 281 h++; 282 pending >>= softirq_bit; 283 } 284 285 rcu_bh_qs(); 286 local_irq_disable(); 287 288 pending = local_softirq_pending(); 289 if (pending) { 290 if (time_before(jiffies, end) && !need_resched() && 291 --max_restart) 292 goto restart; 293 294 wakeup_softirqd(); 295 } 296 297 lockdep_softirq_end(in_hardirq); 298 account_irq_exit_time(current); 299 __local_bh_enable(SOFTIRQ_OFFSET); 300 WARN_ON_ONCE(in_interrupt()); 301 tsk_restore_flags(current, old_flags, PF_MEMALLOC); 302} 303 304asmlinkage __visible void do_softirq(void) 305{ 306 __u32 pending; 307 unsigned long flags; 308 309 if (in_interrupt()) 310 return; 311 312 local_irq_save(flags); 313 314 pending = local_softirq_pending(); 315 316 if (pending) 317 do_softirq_own_stack(); 318 319 local_irq_restore(flags); 320} 321 322/* 323 * Enter an interrupt context. 324 */ 325void irq_enter(void) 326{ 327 rcu_irq_enter(); 328 if (is_idle_task(current) && !in_interrupt()) { 329 /* 330 * Prevent raise_softirq from needlessly waking up ksoftirqd 331 * here, as softirq will be serviced on return from interrupt. 332 */ 333 local_bh_disable(); 334 tick_irq_enter(); 335 _local_bh_enable(); 336 } 337 338 __irq_enter(); 339} 340 341static inline void invoke_softirq(void) 342{ 343 if (!force_irqthreads) { 344#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK 345 /* 346 * We can safely execute softirq on the current stack if 347 * it is the irq stack, because it should be near empty 348 * at this stage. 349 */ 350 __do_softirq(); 351#else 352 /* 353 * Otherwise, irq_exit() is called on the task stack that can 354 * be potentially deep already. So call softirq in its own stack 355 * to prevent from any overrun. 356 */ 357 do_softirq_own_stack(); 358#endif 359 } else { 360 wakeup_softirqd(); 361 } 362} 363 364static inline void tick_irq_exit(void) 365{ 366#ifdef CONFIG_NO_HZ_COMMON 367 int cpu = smp_processor_id(); 368 369 /* Make sure that timer wheel updates are propagated */ 370 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { 371 if (!in_interrupt()) 372 tick_nohz_irq_exit(); 373 } 374#endif 375} 376 377/* 378 * Exit an interrupt context. Process softirqs if needed and possible: 379 */ 380void irq_exit(void) 381{ 382#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED 383 local_irq_disable(); 384#else 385 WARN_ON_ONCE(!irqs_disabled()); 386#endif 387 388 account_irq_exit_time(current); 389 preempt_count_sub(HARDIRQ_OFFSET); 390 if (!in_interrupt() && local_softirq_pending()) 391 invoke_softirq(); 392 393 tick_irq_exit(); 394 rcu_irq_exit(); 395 trace_hardirq_exit(); /* must be last! */ 396} 397 398/* 399 * This function must run with irqs disabled! 400 */ 401inline void raise_softirq_irqoff(unsigned int nr) 402{ 403 __raise_softirq_irqoff(nr); 404 405 /* 406 * If we're in an interrupt or softirq, we're done 407 * (this also catches softirq-disabled code). We will 408 * actually run the softirq once we return from 409 * the irq or softirq. 410 * 411 * Otherwise we wake up ksoftirqd to make sure we 412 * schedule the softirq soon. 413 */ 414 if (!in_interrupt()) 415 wakeup_softirqd(); 416} 417 418void raise_softirq(unsigned int nr) 419{ 420 unsigned long flags; 421 422 local_irq_save(flags); 423 raise_softirq_irqoff(nr); 424 local_irq_restore(flags); 425} 426 427void __raise_softirq_irqoff(unsigned int nr) 428{ 429 trace_softirq_raise(nr); 430 or_softirq_pending(1UL << nr); 431} 432 433void open_softirq(int nr, void (*action)(struct softirq_action *)) 434{ 435 softirq_vec[nr].action = action; 436} 437 438/* 439 * Tasklets 440 */ 441struct tasklet_head { 442 struct tasklet_struct *head; 443 struct tasklet_struct **tail; 444}; 445 446static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); 447static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); 448 449void __tasklet_schedule(struct tasklet_struct *t) 450{ 451 unsigned long flags; 452 453 local_irq_save(flags); 454 t->next = NULL; 455 *__this_cpu_read(tasklet_vec.tail) = t; 456 __this_cpu_write(tasklet_vec.tail, &(t->next)); 457 raise_softirq_irqoff(TASKLET_SOFTIRQ); 458 local_irq_restore(flags); 459} 460EXPORT_SYMBOL(__tasklet_schedule); 461 462void __tasklet_hi_schedule(struct tasklet_struct *t) 463{ 464 unsigned long flags; 465 466 local_irq_save(flags); 467 t->next = NULL; 468 *__this_cpu_read(tasklet_hi_vec.tail) = t; 469 __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); 470 raise_softirq_irqoff(HI_SOFTIRQ); 471 local_irq_restore(flags); 472} 473EXPORT_SYMBOL(__tasklet_hi_schedule); 474 475void __tasklet_hi_schedule_first(struct tasklet_struct *t) 476{ 477 BUG_ON(!irqs_disabled()); 478 479 t->next = __this_cpu_read(tasklet_hi_vec.head); 480 __this_cpu_write(tasklet_hi_vec.head, t); 481 __raise_softirq_irqoff(HI_SOFTIRQ); 482} 483EXPORT_SYMBOL(__tasklet_hi_schedule_first); 484 485static void tasklet_action(struct softirq_action *a) 486{ 487 struct tasklet_struct *list; 488 489 local_irq_disable(); 490 list = __this_cpu_read(tasklet_vec.head); 491 __this_cpu_write(tasklet_vec.head, NULL); 492 __this_cpu_write(tasklet_vec.tail, this_cpu_ptr(&tasklet_vec.head)); 493 local_irq_enable(); 494 495 while (list) { 496 struct tasklet_struct *t = list; 497 498 list = list->next; 499 500 if (tasklet_trylock(t)) { 501 if (!atomic_read(&t->count)) { 502 if (!test_and_clear_bit(TASKLET_STATE_SCHED, 503 &t->state)) 504 BUG(); 505 t->func(t->data); 506 tasklet_unlock(t); 507 continue; 508 } 509 tasklet_unlock(t); 510 } 511 512 local_irq_disable(); 513 t->next = NULL; 514 *__this_cpu_read(tasklet_vec.tail) = t; 515 __this_cpu_write(tasklet_vec.tail, &(t->next)); 516 __raise_softirq_irqoff(TASKLET_SOFTIRQ); 517 local_irq_enable(); 518 } 519} 520 521static void tasklet_hi_action(struct softirq_action *a) 522{ 523 struct tasklet_struct *list; 524 525 local_irq_disable(); 526 list = __this_cpu_read(tasklet_hi_vec.head); 527 __this_cpu_write(tasklet_hi_vec.head, NULL); 528 __this_cpu_write(tasklet_hi_vec.tail, this_cpu_ptr(&tasklet_hi_vec.head)); 529 local_irq_enable(); 530 531 while (list) { 532 struct tasklet_struct *t = list; 533 534 list = list->next; 535 536 if (tasklet_trylock(t)) { 537 if (!atomic_read(&t->count)) { 538 if (!test_and_clear_bit(TASKLET_STATE_SCHED, 539 &t->state)) 540 BUG(); 541 t->func(t->data); 542 tasklet_unlock(t); 543 continue; 544 } 545 tasklet_unlock(t); 546 } 547 548 local_irq_disable(); 549 t->next = NULL; 550 *__this_cpu_read(tasklet_hi_vec.tail) = t; 551 __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); 552 __raise_softirq_irqoff(HI_SOFTIRQ); 553 local_irq_enable(); 554 } 555} 556 557void tasklet_init(struct tasklet_struct *t, 558 void (*func)(unsigned long), unsigned long data) 559{ 560 t->next = NULL; 561 t->state = 0; 562 atomic_set(&t->count, 0); 563 t->func = func; 564 t->data = data; 565} 566EXPORT_SYMBOL(tasklet_init); 567 568void tasklet_kill(struct tasklet_struct *t) 569{ 570 if (in_interrupt()) 571 pr_notice("Attempt to kill tasklet from interrupt\n"); 572 573 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { 574 do { 575 yield(); 576 } while (test_bit(TASKLET_STATE_SCHED, &t->state)); 577 } 578 tasklet_unlock_wait(t); 579 clear_bit(TASKLET_STATE_SCHED, &t->state); 580} 581EXPORT_SYMBOL(tasklet_kill); 582 583/* 584 * tasklet_hrtimer 585 */ 586 587/* 588 * The trampoline is called when the hrtimer expires. It schedules a tasklet 589 * to run __tasklet_hrtimer_trampoline() which in turn will call the intended 590 * hrtimer callback, but from softirq context. 591 */ 592static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer) 593{ 594 struct tasklet_hrtimer *ttimer = 595 container_of(timer, struct tasklet_hrtimer, timer); 596 597 tasklet_hi_schedule(&ttimer->tasklet); 598 return HRTIMER_NORESTART; 599} 600 601/* 602 * Helper function which calls the hrtimer callback from 603 * tasklet/softirq context 604 */ 605static void __tasklet_hrtimer_trampoline(unsigned long data) 606{ 607 struct tasklet_hrtimer *ttimer = (void *)data; 608 enum hrtimer_restart restart; 609 610 restart = ttimer->function(&ttimer->timer); 611 if (restart != HRTIMER_NORESTART) 612 hrtimer_restart(&ttimer->timer); 613} 614 615/** 616 * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks 617 * @ttimer: tasklet_hrtimer which is initialized 618 * @function: hrtimer callback function which gets called from softirq context 619 * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME) 620 * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL) 621 */ 622void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer, 623 enum hrtimer_restart (*function)(struct hrtimer *), 624 clockid_t which_clock, enum hrtimer_mode mode) 625{ 626 hrtimer_init(&ttimer->timer, which_clock, mode); 627 ttimer->timer.function = __hrtimer_tasklet_trampoline; 628 tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline, 629 (unsigned long)ttimer); 630 ttimer->function = function; 631} 632EXPORT_SYMBOL_GPL(tasklet_hrtimer_init); 633 634void __init softirq_init(void) 635{ 636 int cpu; 637 638 for_each_possible_cpu(cpu) { 639 per_cpu(tasklet_vec, cpu).tail = 640 &per_cpu(tasklet_vec, cpu).head; 641 per_cpu(tasklet_hi_vec, cpu).tail = 642 &per_cpu(tasklet_hi_vec, cpu).head; 643 } 644 645 open_softirq(TASKLET_SOFTIRQ, tasklet_action); 646 open_softirq(HI_SOFTIRQ, tasklet_hi_action); 647} 648 649static int ksoftirqd_should_run(unsigned int cpu) 650{ 651 return local_softirq_pending(); 652} 653 654static void run_ksoftirqd(unsigned int cpu) 655{ 656 local_irq_disable(); 657 if (local_softirq_pending()) { 658 /* 659 * We can safely run softirq on inline stack, as we are not deep 660 * in the task stack here. 661 */ 662 __do_softirq(); 663 local_irq_enable(); 664 cond_resched_rcu_qs(); 665 return; 666 } 667 local_irq_enable(); 668} 669 670#ifdef CONFIG_HOTPLUG_CPU 671/* 672 * tasklet_kill_immediate is called to remove a tasklet which can already be 673 * scheduled for execution on @cpu. 674 * 675 * Unlike tasklet_kill, this function removes the tasklet 676 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. 677 * 678 * When this function is called, @cpu must be in the CPU_DEAD state. 679 */ 680void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) 681{ 682 struct tasklet_struct **i; 683 684 BUG_ON(cpu_online(cpu)); 685 BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); 686 687 if (!test_bit(TASKLET_STATE_SCHED, &t->state)) 688 return; 689 690 /* CPU is dead, so no lock needed. */ 691 for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { 692 if (*i == t) { 693 *i = t->next; 694 /* If this was the tail element, move the tail ptr */ 695 if (*i == NULL) 696 per_cpu(tasklet_vec, cpu).tail = i; 697 return; 698 } 699 } 700 BUG(); 701} 702 703static void takeover_tasklets(unsigned int cpu) 704{ 705 /* CPU is dead, so no lock needed. */ 706 local_irq_disable(); 707 708 /* Find end, append list for that CPU. */ 709 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { 710 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; 711 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); 712 per_cpu(tasklet_vec, cpu).head = NULL; 713 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; 714 } 715 raise_softirq_irqoff(TASKLET_SOFTIRQ); 716 717 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { 718 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; 719 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); 720 per_cpu(tasklet_hi_vec, cpu).head = NULL; 721 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; 722 } 723 raise_softirq_irqoff(HI_SOFTIRQ); 724 725 local_irq_enable(); 726} 727#endif /* CONFIG_HOTPLUG_CPU */ 728 729static int cpu_callback(struct notifier_block *nfb, unsigned long action, 730 void *hcpu) 731{ 732 switch (action) { 733#ifdef CONFIG_HOTPLUG_CPU 734 case CPU_DEAD: 735 case CPU_DEAD_FROZEN: 736 takeover_tasklets((unsigned long)hcpu); 737 break; 738#endif /* CONFIG_HOTPLUG_CPU */ 739 } 740 return NOTIFY_OK; 741} 742 743static struct notifier_block cpu_nfb = { 744 .notifier_call = cpu_callback 745}; 746 747static struct smp_hotplug_thread softirq_threads = { 748 .store = &ksoftirqd, 749 .thread_should_run = ksoftirqd_should_run, 750 .thread_fn = run_ksoftirqd, 751 .thread_comm = "ksoftirqd/%u", 752}; 753 754static __init int spawn_ksoftirqd(void) 755{ 756 register_cpu_notifier(&cpu_nfb); 757 758 BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); 759 760 return 0; 761} 762early_initcall(spawn_ksoftirqd); 763 764/* 765 * [ These __weak aliases are kept in a separate compilation unit, so that 766 * GCC does not inline them incorrectly. ] 767 */ 768 769int __init __weak early_irq_init(void) 770{ 771 return 0; 772} 773 774int __init __weak arch_probe_nr_irqs(void) 775{ 776 return NR_IRQS_LEGACY; 777} 778 779int __init __weak arch_early_irq_init(void) 780{ 781 return 0; 782} 783 784unsigned int __weak arch_dynirq_lower_bound(unsigned int from) 785{ 786 return from; 787} 788