1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * linux/kernel/softirq.c 4 * 5 * Copyright (C) 1992 Linus Torvalds 6 * 7 * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) 8 */ 9 10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 11 12#include <linux/export.h> 13#include <linux/kernel_stat.h> 14#include <linux/interrupt.h> 15#include <linux/init.h> 16#include <linux/local_lock.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#include <linux/wait_bit.h> 30#include <linux/workqueue.h> 31 32#include <asm/softirq_stack.h> 33 34#define CREATE_TRACE_POINTS 35#include <trace/events/irq.h> 36 37/* 38 - No shared variables, all the data are CPU local. 39 - If a softirq needs serialization, let it serialize itself 40 by its own spinlocks. 41 - Even if softirq is serialized, only local cpu is marked for 42 execution. Hence, we get something sort of weak cpu binding. 43 Though it is still not clear, will it result in better locality 44 or will not. 45 46 Examples: 47 - NET RX softirq. It is multithreaded and does not require 48 any global serialization. 49 - NET TX softirq. It kicks software netdevice queues, hence 50 it is logically serialized per device, but this serialization 51 is invisible to common code. 52 - Tasklets: serialized wrt itself. 53 */ 54 55#ifndef __ARCH_IRQ_STAT 56DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat); 57EXPORT_PER_CPU_SYMBOL(irq_stat); 58#endif 59 60static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; 61 62DEFINE_PER_CPU(struct task_struct *, ksoftirqd); 63 64const char * const softirq_to_name[NR_SOFTIRQS] = { 65 "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL", 66 "TASKLET", "SCHED", "HRTIMER", "RCU" 67}; 68 69/* 70 * we cannot loop indefinitely here to avoid userspace starvation, 71 * but we also don't want to introduce a worst case 1/HZ latency 72 * to the pending events, so lets the scheduler to balance 73 * the softirq load for us. 74 */ 75static void wakeup_softirqd(void) 76{ 77 /* Interrupts are disabled: no need to stop preemption */ 78 struct task_struct *tsk = __this_cpu_read(ksoftirqd); 79 80 if (tsk) 81 wake_up_process(tsk); 82} 83 84#ifdef CONFIG_TRACE_IRQFLAGS 85DEFINE_PER_CPU(int, hardirqs_enabled); 86DEFINE_PER_CPU(int, hardirq_context); 87EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled); 88EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context); 89#endif 90 91/* 92 * SOFTIRQ_OFFSET usage: 93 * 94 * On !RT kernels 'count' is the preempt counter, on RT kernels this applies 95 * to a per CPU counter and to task::softirqs_disabled_cnt. 96 * 97 * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq 98 * processing. 99 * 100 * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) 101 * on local_bh_disable or local_bh_enable. 102 * 103 * This lets us distinguish between whether we are currently processing 104 * softirq and whether we just have bh disabled. 105 */ 106#ifdef CONFIG_PREEMPT_RT 107 108/* 109 * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and 110 * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a 111 * softirq disabled section to be preempted. 112 * 113 * The per task counter is used for softirq_count(), in_softirq() and 114 * in_serving_softirqs() because these counts are only valid when the task 115 * holding softirq_ctrl::lock is running. 116 * 117 * The per CPU counter prevents pointless wakeups of ksoftirqd in case that 118 * the task which is in a softirq disabled section is preempted or blocks. 119 */ 120struct softirq_ctrl { 121 local_lock_t lock; 122 int cnt; 123}; 124 125static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { 126 .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock), 127}; 128 129/** 130 * local_bh_blocked() - Check for idle whether BH processing is blocked 131 * 132 * Returns false if the per CPU softirq::cnt is 0 otherwise true. 133 * 134 * This is invoked from the idle task to guard against false positive 135 * softirq pending warnings, which would happen when the task which holds 136 * softirq_ctrl::lock was the only running task on the CPU and blocks on 137 * some other lock. 138 */ 139bool local_bh_blocked(void) 140{ 141 return __this_cpu_read(softirq_ctrl.cnt) != 0; 142} 143 144void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) 145{ 146 unsigned long flags; 147 int newcnt; 148 149 WARN_ON_ONCE(in_hardirq()); 150 151 /* First entry of a task into a BH disabled section? */ 152 if (!current->softirq_disable_cnt) { 153 if (preemptible()) { 154 local_lock(&softirq_ctrl.lock); 155 /* Required to meet the RCU bottomhalf requirements. */ 156 rcu_read_lock(); 157 } else { 158 DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)); 159 } 160 } 161 162 /* 163 * Track the per CPU softirq disabled state. On RT this is per CPU 164 * state to allow preemption of bottom half disabled sections. 165 */ 166 newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt); 167 /* 168 * Reflect the result in the task state to prevent recursion on the 169 * local lock and to make softirq_count() & al work. 170 */ 171 current->softirq_disable_cnt = newcnt; 172 173 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) { 174 raw_local_irq_save(flags); 175 lockdep_softirqs_off(ip); 176 raw_local_irq_restore(flags); 177 } 178} 179EXPORT_SYMBOL(__local_bh_disable_ip); 180 181static void __local_bh_enable(unsigned int cnt, bool unlock) 182{ 183 unsigned long flags; 184 int newcnt; 185 186 DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt != 187 this_cpu_read(softirq_ctrl.cnt)); 188 189 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) { 190 raw_local_irq_save(flags); 191 lockdep_softirqs_on(_RET_IP_); 192 raw_local_irq_restore(flags); 193 } 194 195 newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt); 196 current->softirq_disable_cnt = newcnt; 197 198 if (!newcnt && unlock) { 199 rcu_read_unlock(); 200 local_unlock(&softirq_ctrl.lock); 201 } 202} 203 204void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) 205{ 206 bool preempt_on = preemptible(); 207 unsigned long flags; 208 u32 pending; 209 int curcnt; 210 211 WARN_ON_ONCE(in_hardirq()); 212 lockdep_assert_irqs_enabled(); 213 214 local_irq_save(flags); 215 curcnt = __this_cpu_read(softirq_ctrl.cnt); 216 217 /* 218 * If this is not reenabling soft interrupts, no point in trying to 219 * run pending ones. 220 */ 221 if (curcnt != cnt) 222 goto out; 223 224 pending = local_softirq_pending(); 225 if (!pending) 226 goto out; 227 228 /* 229 * If this was called from non preemptible context, wake up the 230 * softirq daemon. 231 */ 232 if (!preempt_on) { 233 wakeup_softirqd(); 234 goto out; 235 } 236 237 /* 238 * Adjust softirq count to SOFTIRQ_OFFSET which makes 239 * in_serving_softirq() become true. 240 */ 241 cnt = SOFTIRQ_OFFSET; 242 __local_bh_enable(cnt, false); 243 __do_softirq(); 244 245out: 246 __local_bh_enable(cnt, preempt_on); 247 local_irq_restore(flags); 248} 249EXPORT_SYMBOL(__local_bh_enable_ip); 250 251/* 252 * Invoked from ksoftirqd_run() outside of the interrupt disabled section 253 * to acquire the per CPU local lock for reentrancy protection. 254 */ 255static inline void ksoftirqd_run_begin(void) 256{ 257 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); 258 local_irq_disable(); 259} 260 261/* Counterpart to ksoftirqd_run_begin() */ 262static inline void ksoftirqd_run_end(void) 263{ 264 __local_bh_enable(SOFTIRQ_OFFSET, true); 265 WARN_ON_ONCE(in_interrupt()); 266 local_irq_enable(); 267} 268 269static inline void softirq_handle_begin(void) { } 270static inline void softirq_handle_end(void) { } 271 272static inline bool should_wake_ksoftirqd(void) 273{ 274 return !this_cpu_read(softirq_ctrl.cnt); 275} 276 277static inline void invoke_softirq(void) 278{ 279 if (should_wake_ksoftirqd()) 280 wakeup_softirqd(); 281} 282 283/* 284 * flush_smp_call_function_queue() can raise a soft interrupt in a function 285 * call. On RT kernels this is undesired and the only known functionality 286 * in the block layer which does this is disabled on RT. If soft interrupts 287 * get raised which haven't been raised before the flush, warn so it can be 288 * investigated. 289 */ 290void do_softirq_post_smp_call_flush(unsigned int was_pending) 291{ 292 if (WARN_ON_ONCE(was_pending != local_softirq_pending())) 293 invoke_softirq(); 294} 295 296#else /* CONFIG_PREEMPT_RT */ 297 298/* 299 * This one is for softirq.c-internal use, where hardirqs are disabled 300 * legitimately: 301 */ 302#ifdef CONFIG_TRACE_IRQFLAGS 303void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) 304{ 305 unsigned long flags; 306 307 WARN_ON_ONCE(in_hardirq()); 308 309 raw_local_irq_save(flags); 310 /* 311 * The preempt tracer hooks into preempt_count_add and will break 312 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET 313 * is set and before current->softirq_enabled is cleared. 314 * We must manually increment preempt_count here and manually 315 * call the trace_preempt_off later. 316 */ 317 __preempt_count_add(cnt); 318 /* 319 * Were softirqs turned off above: 320 */ 321 if (softirq_count() == (cnt & SOFTIRQ_MASK)) 322 lockdep_softirqs_off(ip); 323 raw_local_irq_restore(flags); 324 325 if (preempt_count() == cnt) { 326#ifdef CONFIG_DEBUG_PREEMPT 327 current->preempt_disable_ip = get_lock_parent_ip(); 328#endif 329 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip()); 330 } 331} 332EXPORT_SYMBOL(__local_bh_disable_ip); 333#endif /* CONFIG_TRACE_IRQFLAGS */ 334 335static void __local_bh_enable(unsigned int cnt) 336{ 337 lockdep_assert_irqs_disabled(); 338 339 if (preempt_count() == cnt) 340 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); 341 342 if (softirq_count() == (cnt & SOFTIRQ_MASK)) 343 lockdep_softirqs_on(_RET_IP_); 344 345 __preempt_count_sub(cnt); 346} 347 348/* 349 * Special-case - softirqs can safely be enabled by __do_softirq(), 350 * without processing still-pending softirqs: 351 */ 352void _local_bh_enable(void) 353{ 354 WARN_ON_ONCE(in_hardirq()); 355 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); 356} 357EXPORT_SYMBOL(_local_bh_enable); 358 359void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) 360{ 361 WARN_ON_ONCE(in_hardirq()); 362 lockdep_assert_irqs_enabled(); 363#ifdef CONFIG_TRACE_IRQFLAGS 364 local_irq_disable(); 365#endif 366 /* 367 * Are softirqs going to be turned on now: 368 */ 369 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) 370 lockdep_softirqs_on(ip); 371 /* 372 * Keep preemption disabled until we are done with 373 * softirq processing: 374 */ 375 __preempt_count_sub(cnt - 1); 376 377 if (unlikely(!in_interrupt() && local_softirq_pending())) { 378 /* 379 * Run softirq if any pending. And do it in its own stack 380 * as we may be calling this deep in a task call stack already. 381 */ 382 do_softirq(); 383 } 384 385 preempt_count_dec(); 386#ifdef CONFIG_TRACE_IRQFLAGS 387 local_irq_enable(); 388#endif 389 preempt_check_resched(); 390} 391EXPORT_SYMBOL(__local_bh_enable_ip); 392 393static inline void softirq_handle_begin(void) 394{ 395 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); 396} 397 398static inline void softirq_handle_end(void) 399{ 400 __local_bh_enable(SOFTIRQ_OFFSET); 401 WARN_ON_ONCE(in_interrupt()); 402} 403 404static inline void ksoftirqd_run_begin(void) 405{ 406 local_irq_disable(); 407} 408 409static inline void ksoftirqd_run_end(void) 410{ 411 local_irq_enable(); 412} 413 414static inline bool should_wake_ksoftirqd(void) 415{ 416 return true; 417} 418 419static inline void invoke_softirq(void) 420{ 421 if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) { 422#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK 423 /* 424 * We can safely execute softirq on the current stack if 425 * it is the irq stack, because it should be near empty 426 * at this stage. 427 */ 428 __do_softirq(); 429#else 430 /* 431 * Otherwise, irq_exit() is called on the task stack that can 432 * be potentially deep already. So call softirq in its own stack 433 * to prevent from any overrun. 434 */ 435 do_softirq_own_stack(); 436#endif 437 } else { 438 wakeup_softirqd(); 439 } 440} 441 442asmlinkage __visible void do_softirq(void) 443{ 444 __u32 pending; 445 unsigned long flags; 446 447 if (in_interrupt()) 448 return; 449 450 local_irq_save(flags); 451 452 pending = local_softirq_pending(); 453 454 if (pending) 455 do_softirq_own_stack(); 456 457 local_irq_restore(flags); 458} 459 460#endif /* !CONFIG_PREEMPT_RT */ 461 462/* 463 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, 464 * but break the loop if need_resched() is set or after 2 ms. 465 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in 466 * certain cases, such as stop_machine(), jiffies may cease to 467 * increment and so we need the MAX_SOFTIRQ_RESTART limit as 468 * well to make sure we eventually return from this method. 469 * 470 * These limits have been established via experimentation. 471 * The two things to balance is latency against fairness - 472 * we want to handle softirqs as soon as possible, but they 473 * should not be able to lock up the box. 474 */ 475#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) 476#define MAX_SOFTIRQ_RESTART 10 477 478#ifdef CONFIG_TRACE_IRQFLAGS 479/* 480 * When we run softirqs from irq_exit() and thus on the hardirq stack we need 481 * to keep the lockdep irq context tracking as tight as possible in order to 482 * not miss-qualify lock contexts and miss possible deadlocks. 483 */ 484 485static inline bool lockdep_softirq_start(void) 486{ 487 bool in_hardirq = false; 488 489 if (lockdep_hardirq_context()) { 490 in_hardirq = true; 491 lockdep_hardirq_exit(); 492 } 493 494 lockdep_softirq_enter(); 495 496 return in_hardirq; 497} 498 499static inline void lockdep_softirq_end(bool in_hardirq) 500{ 501 lockdep_softirq_exit(); 502 503 if (in_hardirq) 504 lockdep_hardirq_enter(); 505} 506#else 507static inline bool lockdep_softirq_start(void) { return false; } 508static inline void lockdep_softirq_end(bool in_hardirq) { } 509#endif 510 511static void handle_softirqs(bool ksirqd) 512{ 513 unsigned long end = jiffies + MAX_SOFTIRQ_TIME; 514 unsigned long old_flags = current->flags; 515 int max_restart = MAX_SOFTIRQ_RESTART; 516 struct softirq_action *h; 517 bool in_hardirq; 518 __u32 pending; 519 int softirq_bit; 520 521 /* 522 * Mask out PF_MEMALLOC as the current task context is borrowed for the 523 * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC 524 * again if the socket is related to swapping. 525 */ 526 current->flags &= ~PF_MEMALLOC; 527 528 pending = local_softirq_pending(); 529 530 softirq_handle_begin(); 531 in_hardirq = lockdep_softirq_start(); 532 account_softirq_enter(current); 533 534restart: 535 /* Reset the pending bitmask before enabling irqs */ 536 set_softirq_pending(0); 537 538 local_irq_enable(); 539 540 h = softirq_vec; 541 542 while ((softirq_bit = ffs(pending))) { 543 unsigned int vec_nr; 544 int prev_count; 545 546 h += softirq_bit - 1; 547 548 vec_nr = h - softirq_vec; 549 prev_count = preempt_count(); 550 551 kstat_incr_softirqs_this_cpu(vec_nr); 552 553 trace_softirq_entry(vec_nr); 554 h->action(h); 555 trace_softirq_exit(vec_nr); 556 if (unlikely(prev_count != preempt_count())) { 557 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n", 558 vec_nr, softirq_to_name[vec_nr], h->action, 559 prev_count, preempt_count()); 560 preempt_count_set(prev_count); 561 } 562 h++; 563 pending >>= softirq_bit; 564 } 565 566 if (!IS_ENABLED(CONFIG_PREEMPT_RT) && ksirqd) 567 rcu_softirq_qs(); 568 569 local_irq_disable(); 570 571 pending = local_softirq_pending(); 572 if (pending) { 573 if (time_before(jiffies, end) && !need_resched() && 574 --max_restart) 575 goto restart; 576 577 wakeup_softirqd(); 578 } 579 580 account_softirq_exit(current); 581 lockdep_softirq_end(in_hardirq); 582 softirq_handle_end(); 583 current_restore_flags(old_flags, PF_MEMALLOC); 584} 585 586asmlinkage __visible void __softirq_entry __do_softirq(void) 587{ 588 handle_softirqs(false); 589} 590 591/** 592 * irq_enter_rcu - Enter an interrupt context with RCU watching 593 */ 594void irq_enter_rcu(void) 595{ 596 __irq_enter_raw(); 597 598 if (tick_nohz_full_cpu(smp_processor_id()) || 599 (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET))) 600 tick_irq_enter(); 601 602 account_hardirq_enter(current); 603} 604 605/** 606 * irq_enter - Enter an interrupt context including RCU update 607 */ 608void irq_enter(void) 609{ 610 ct_irq_enter(); 611 irq_enter_rcu(); 612} 613 614static inline void tick_irq_exit(void) 615{ 616#ifdef CONFIG_NO_HZ_COMMON 617 int cpu = smp_processor_id(); 618 619 /* Make sure that timer wheel updates are propagated */ 620 if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { 621 if (!in_hardirq()) 622 tick_nohz_irq_exit(); 623 } 624#endif 625} 626 627static inline void __irq_exit_rcu(void) 628{ 629#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED 630 local_irq_disable(); 631#else 632 lockdep_assert_irqs_disabled(); 633#endif 634 account_hardirq_exit(current); 635 preempt_count_sub(HARDIRQ_OFFSET); 636 if (!in_interrupt() && local_softirq_pending()) 637 invoke_softirq(); 638 639 tick_irq_exit(); 640} 641 642/** 643 * irq_exit_rcu() - Exit an interrupt context without updating RCU 644 * 645 * Also processes softirqs if needed and possible. 646 */ 647void irq_exit_rcu(void) 648{ 649 __irq_exit_rcu(); 650 /* must be last! */ 651 lockdep_hardirq_exit(); 652} 653 654/** 655 * irq_exit - Exit an interrupt context, update RCU and lockdep 656 * 657 * Also processes softirqs if needed and possible. 658 */ 659void irq_exit(void) 660{ 661 __irq_exit_rcu(); 662 ct_irq_exit(); 663 /* must be last! */ 664 lockdep_hardirq_exit(); 665} 666 667/* 668 * This function must run with irqs disabled! 669 */ 670inline void raise_softirq_irqoff(unsigned int nr) 671{ 672 __raise_softirq_irqoff(nr); 673 674 /* 675 * If we're in an interrupt or softirq, we're done 676 * (this also catches softirq-disabled code). We will 677 * actually run the softirq once we return from 678 * the irq or softirq. 679 * 680 * Otherwise we wake up ksoftirqd to make sure we 681 * schedule the softirq soon. 682 */ 683 if (!in_interrupt() && should_wake_ksoftirqd()) 684 wakeup_softirqd(); 685} 686 687void raise_softirq(unsigned int nr) 688{ 689 unsigned long flags; 690 691 local_irq_save(flags); 692 raise_softirq_irqoff(nr); 693 local_irq_restore(flags); 694} 695 696void __raise_softirq_irqoff(unsigned int nr) 697{ 698 lockdep_assert_irqs_disabled(); 699 trace_softirq_raise(nr); 700 or_softirq_pending(1UL << nr); 701} 702 703void open_softirq(int nr, void (*action)(struct softirq_action *)) 704{ 705 softirq_vec[nr].action = action; 706} 707 708/* 709 * Tasklets 710 */ 711struct tasklet_head { 712 struct tasklet_struct *head; 713 struct tasklet_struct **tail; 714}; 715 716static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); 717static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); 718 719static void __tasklet_schedule_common(struct tasklet_struct *t, 720 struct tasklet_head __percpu *headp, 721 unsigned int softirq_nr) 722{ 723 struct tasklet_head *head; 724 unsigned long flags; 725 726 local_irq_save(flags); 727 head = this_cpu_ptr(headp); 728 t->next = NULL; 729 *head->tail = t; 730 head->tail = &(t->next); 731 raise_softirq_irqoff(softirq_nr); 732 local_irq_restore(flags); 733} 734 735void __tasklet_schedule(struct tasklet_struct *t) 736{ 737 __tasklet_schedule_common(t, &tasklet_vec, 738 TASKLET_SOFTIRQ); 739} 740EXPORT_SYMBOL(__tasklet_schedule); 741 742void __tasklet_hi_schedule(struct tasklet_struct *t) 743{ 744 __tasklet_schedule_common(t, &tasklet_hi_vec, 745 HI_SOFTIRQ); 746} 747EXPORT_SYMBOL(__tasklet_hi_schedule); 748 749static bool tasklet_clear_sched(struct tasklet_struct *t) 750{ 751 if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) { 752 wake_up_var(&t->state); 753 return true; 754 } 755 756 WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n", 757 t->use_callback ? "callback" : "func", 758 t->use_callback ? (void *)t->callback : (void *)t->func); 759 760 return false; 761} 762 763static void tasklet_action_common(struct softirq_action *a, 764 struct tasklet_head *tl_head, 765 unsigned int softirq_nr) 766{ 767 struct tasklet_struct *list; 768 769 local_irq_disable(); 770 list = tl_head->head; 771 tl_head->head = NULL; 772 tl_head->tail = &tl_head->head; 773 local_irq_enable(); 774 775 while (list) { 776 struct tasklet_struct *t = list; 777 778 list = list->next; 779 780 if (tasklet_trylock(t)) { 781 if (!atomic_read(&t->count)) { 782 if (tasklet_clear_sched(t)) { 783 if (t->use_callback) { 784 trace_tasklet_entry(t, t->callback); 785 t->callback(t); 786 trace_tasklet_exit(t, t->callback); 787 } else { 788 trace_tasklet_entry(t, t->func); 789 t->func(t->data); 790 trace_tasklet_exit(t, t->func); 791 } 792 } 793 tasklet_unlock(t); 794 continue; 795 } 796 tasklet_unlock(t); 797 } 798 799 local_irq_disable(); 800 t->next = NULL; 801 *tl_head->tail = t; 802 tl_head->tail = &t->next; 803 __raise_softirq_irqoff(softirq_nr); 804 local_irq_enable(); 805 } 806} 807 808static __latent_entropy void tasklet_action(struct softirq_action *a) 809{ 810 workqueue_softirq_action(false); 811 tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ); 812} 813 814static __latent_entropy void tasklet_hi_action(struct softirq_action *a) 815{ 816 workqueue_softirq_action(true); 817 tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ); 818} 819 820void tasklet_setup(struct tasklet_struct *t, 821 void (*callback)(struct tasklet_struct *)) 822{ 823 t->next = NULL; 824 t->state = 0; 825 atomic_set(&t->count, 0); 826 t->callback = callback; 827 t->use_callback = true; 828 t->data = 0; 829} 830EXPORT_SYMBOL(tasklet_setup); 831 832void tasklet_init(struct tasklet_struct *t, 833 void (*func)(unsigned long), unsigned long data) 834{ 835 t->next = NULL; 836 t->state = 0; 837 atomic_set(&t->count, 0); 838 t->func = func; 839 t->use_callback = false; 840 t->data = data; 841} 842EXPORT_SYMBOL(tasklet_init); 843 844#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) 845/* 846 * Do not use in new code. Waiting for tasklets from atomic contexts is 847 * error prone and should be avoided. 848 */ 849void tasklet_unlock_spin_wait(struct tasklet_struct *t) 850{ 851 while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { 852 if (IS_ENABLED(CONFIG_PREEMPT_RT)) { 853 /* 854 * Prevent a live lock when current preempted soft 855 * interrupt processing or prevents ksoftirqd from 856 * running. If the tasklet runs on a different CPU 857 * then this has no effect other than doing the BH 858 * disable/enable dance for nothing. 859 */ 860 local_bh_disable(); 861 local_bh_enable(); 862 } else { 863 cpu_relax(); 864 } 865 } 866} 867EXPORT_SYMBOL(tasklet_unlock_spin_wait); 868#endif 869 870void tasklet_kill(struct tasklet_struct *t) 871{ 872 if (in_interrupt()) 873 pr_notice("Attempt to kill tasklet from interrupt\n"); 874 875 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) 876 wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state)); 877 878 tasklet_unlock_wait(t); 879 tasklet_clear_sched(t); 880} 881EXPORT_SYMBOL(tasklet_kill); 882 883#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) 884void tasklet_unlock(struct tasklet_struct *t) 885{ 886 smp_mb__before_atomic(); 887 clear_bit(TASKLET_STATE_RUN, &t->state); 888 smp_mb__after_atomic(); 889 wake_up_var(&t->state); 890} 891EXPORT_SYMBOL_GPL(tasklet_unlock); 892 893void tasklet_unlock_wait(struct tasklet_struct *t) 894{ 895 wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state)); 896} 897EXPORT_SYMBOL_GPL(tasklet_unlock_wait); 898#endif 899 900void __init softirq_init(void) 901{ 902 int cpu; 903 904 for_each_possible_cpu(cpu) { 905 per_cpu(tasklet_vec, cpu).tail = 906 &per_cpu(tasklet_vec, cpu).head; 907 per_cpu(tasklet_hi_vec, cpu).tail = 908 &per_cpu(tasklet_hi_vec, cpu).head; 909 } 910 911 open_softirq(TASKLET_SOFTIRQ, tasklet_action); 912 open_softirq(HI_SOFTIRQ, tasklet_hi_action); 913} 914 915static int ksoftirqd_should_run(unsigned int cpu) 916{ 917 return local_softirq_pending(); 918} 919 920static void run_ksoftirqd(unsigned int cpu) 921{ 922 ksoftirqd_run_begin(); 923 if (local_softirq_pending()) { 924 /* 925 * We can safely run softirq on inline stack, as we are not deep 926 * in the task stack here. 927 */ 928 handle_softirqs(true); 929 ksoftirqd_run_end(); 930 cond_resched(); 931 return; 932 } 933 ksoftirqd_run_end(); 934} 935 936#ifdef CONFIG_HOTPLUG_CPU 937static int takeover_tasklets(unsigned int cpu) 938{ 939 workqueue_softirq_dead(cpu); 940 941 /* CPU is dead, so no lock needed. */ 942 local_irq_disable(); 943 944 /* Find end, append list for that CPU. */ 945 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { 946 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; 947 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); 948 per_cpu(tasklet_vec, cpu).head = NULL; 949 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; 950 } 951 raise_softirq_irqoff(TASKLET_SOFTIRQ); 952 953 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { 954 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; 955 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); 956 per_cpu(tasklet_hi_vec, cpu).head = NULL; 957 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; 958 } 959 raise_softirq_irqoff(HI_SOFTIRQ); 960 961 local_irq_enable(); 962 return 0; 963} 964#else 965#define takeover_tasklets NULL 966#endif /* CONFIG_HOTPLUG_CPU */ 967 968static struct smp_hotplug_thread softirq_threads = { 969 .store = &ksoftirqd, 970 .thread_should_run = ksoftirqd_should_run, 971 .thread_fn = run_ksoftirqd, 972 .thread_comm = "ksoftirqd/%u", 973}; 974 975static __init int spawn_ksoftirqd(void) 976{ 977 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL, 978 takeover_tasklets); 979 BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); 980 981 return 0; 982} 983early_initcall(spawn_ksoftirqd); 984 985/* 986 * [ These __weak aliases are kept in a separate compilation unit, so that 987 * GCC does not inline them incorrectly. ] 988 */ 989 990int __init __weak early_irq_init(void) 991{ 992 return 0; 993} 994 995int __init __weak arch_probe_nr_irqs(void) 996{ 997 return NR_IRQS_LEGACY; 998} 999 1000int __init __weak arch_early_irq_init(void) 1001{ 1002 return 0; 1003} 1004 1005unsigned int __weak arch_dynirq_lower_bound(unsigned int from) 1006{ 1007 return from; 1008} 1009