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