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