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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#ifdef CONFIG_DEBUG_PREEMPT
119 current->preempt_disable_ip = get_lock_parent_ip();
120#endif
121 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
122 }
123}
124EXPORT_SYMBOL(__local_bh_disable_ip);
125#endif /* CONFIG_TRACE_IRQFLAGS */
126
127static void __local_bh_enable(unsigned int cnt)
128{
129 WARN_ON_ONCE(!irqs_disabled());
130
131 if (softirq_count() == (cnt & SOFTIRQ_MASK))
132 trace_softirqs_on(_RET_IP_);
133 preempt_count_sub(cnt);
134}
135
136/*
137 * Special-case - softirqs can safely be enabled in
138 * cond_resched_softirq(), or by __do_softirq(),
139 * without processing still-pending softirqs:
140 */
141void _local_bh_enable(void)
142{
143 WARN_ON_ONCE(in_irq());
144 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
145}
146EXPORT_SYMBOL(_local_bh_enable);
147
148void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
149{
150 WARN_ON_ONCE(in_irq() || irqs_disabled());
151#ifdef CONFIG_TRACE_IRQFLAGS
152 local_irq_disable();
153#endif
154 /*
155 * Are softirqs going to be turned on now:
156 */
157 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
158 trace_softirqs_on(ip);
159 /*
160 * Keep preemption disabled until we are done with
161 * softirq processing:
162 */
163 preempt_count_sub(cnt - 1);
164
165 if (unlikely(!in_interrupt() && local_softirq_pending())) {
166 /*
167 * Run softirq if any pending. And do it in its own stack
168 * as we may be calling this deep in a task call stack already.
169 */
170 do_softirq();
171 }
172
173 preempt_count_dec();
174#ifdef CONFIG_TRACE_IRQFLAGS
175 local_irq_enable();
176#endif
177 preempt_check_resched();
178}
179EXPORT_SYMBOL(__local_bh_enable_ip);
180
181/*
182 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
183 * but break the loop if need_resched() is set or after 2 ms.
184 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
185 * certain cases, such as stop_machine(), jiffies may cease to
186 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
187 * well to make sure we eventually return from this method.
188 *
189 * These limits have been established via experimentation.
190 * The two things to balance is latency against fairness -
191 * we want to handle softirqs as soon as possible, but they
192 * should not be able to lock up the box.
193 */
194#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
195#define MAX_SOFTIRQ_RESTART 10
196
197#ifdef CONFIG_TRACE_IRQFLAGS
198/*
199 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
200 * to keep the lockdep irq context tracking as tight as possible in order to
201 * not miss-qualify lock contexts and miss possible deadlocks.
202 */
203
204static inline bool lockdep_softirq_start(void)
205{
206 bool in_hardirq = false;
207
208 if (trace_hardirq_context(current)) {
209 in_hardirq = true;
210 trace_hardirq_exit();
211 }
212
213 lockdep_softirq_enter();
214
215 return in_hardirq;
216}
217
218static inline void lockdep_softirq_end(bool in_hardirq)
219{
220 lockdep_softirq_exit();
221
222 if (in_hardirq)
223 trace_hardirq_enter();
224}
225#else
226static inline bool lockdep_softirq_start(void) { return false; }
227static inline void lockdep_softirq_end(bool in_hardirq) { }
228#endif
229
230asmlinkage __visible void __softirq_entry __do_softirq(void)
231{
232 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
233 unsigned long old_flags = current->flags;
234 int max_restart = MAX_SOFTIRQ_RESTART;
235 struct softirq_action *h;
236 bool in_hardirq;
237 __u32 pending;
238 int softirq_bit;
239
240 /*
241 * Mask out PF_MEMALLOC s current task context is borrowed for the
242 * softirq. A softirq handled such as network RX might set PF_MEMALLOC
243 * again if the socket is related to swap
244 */
245 current->flags &= ~PF_MEMALLOC;
246
247 pending = local_softirq_pending();
248 account_irq_enter_time(current);
249
250 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
251 in_hardirq = lockdep_softirq_start();
252
253restart:
254 /* Reset the pending bitmask before enabling irqs */
255 set_softirq_pending(0);
256
257 local_irq_enable();
258
259 h = softirq_vec;
260
261 while ((softirq_bit = ffs(pending))) {
262 unsigned int vec_nr;
263 int prev_count;
264
265 h += softirq_bit - 1;
266
267 vec_nr = h - softirq_vec;
268 prev_count = preempt_count();
269
270 kstat_incr_softirqs_this_cpu(vec_nr);
271
272 trace_softirq_entry(vec_nr);
273 h->action(h);
274 trace_softirq_exit(vec_nr);
275 if (unlikely(prev_count != preempt_count())) {
276 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
277 vec_nr, softirq_to_name[vec_nr], h->action,
278 prev_count, preempt_count());
279 preempt_count_set(prev_count);
280 }
281 h++;
282 pending >>= softirq_bit;
283 }
284
285 rcu_bh_qs();
286 local_irq_disable();
287
288 pending = local_softirq_pending();
289 if (pending) {
290 if (time_before(jiffies, end) && !need_resched() &&
291 --max_restart)
292 goto restart;
293
294 wakeup_softirqd();
295 }
296
297 lockdep_softirq_end(in_hardirq);
298 account_irq_exit_time(current);
299 __local_bh_enable(SOFTIRQ_OFFSET);
300 WARN_ON_ONCE(in_interrupt());
301 tsk_restore_flags(current, old_flags, PF_MEMALLOC);
302}
303
304asmlinkage __visible void do_softirq(void)
305{
306 __u32 pending;
307 unsigned long flags;
308
309 if (in_interrupt())
310 return;
311
312 local_irq_save(flags);
313
314 pending = local_softirq_pending();
315
316 if (pending)
317 do_softirq_own_stack();
318
319 local_irq_restore(flags);
320}
321
322/*
323 * Enter an interrupt context.
324 */
325void irq_enter(void)
326{
327 rcu_irq_enter();
328 if (is_idle_task(current) && !in_interrupt()) {
329 /*
330 * Prevent raise_softirq from needlessly waking up ksoftirqd
331 * here, as softirq will be serviced on return from interrupt.
332 */
333 local_bh_disable();
334 tick_irq_enter();
335 _local_bh_enable();
336 }
337
338 __irq_enter();
339}
340
341static inline void invoke_softirq(void)
342{
343 if (!force_irqthreads) {
344#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
345 /*
346 * We can safely execute softirq on the current stack if
347 * it is the irq stack, because it should be near empty
348 * at this stage.
349 */
350 __do_softirq();
351#else
352 /*
353 * Otherwise, irq_exit() is called on the task stack that can
354 * be potentially deep already. So call softirq in its own stack
355 * to prevent from any overrun.
356 */
357 do_softirq_own_stack();
358#endif
359 } else {
360 wakeup_softirqd();
361 }
362}
363
364static inline void tick_irq_exit(void)
365{
366#ifdef CONFIG_NO_HZ_COMMON
367 int cpu = smp_processor_id();
368
369 /* Make sure that timer wheel updates are propagated */
370 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
371 if (!in_interrupt())
372 tick_nohz_irq_exit();
373 }
374#endif
375}
376
377/*
378 * Exit an interrupt context. Process softirqs if needed and possible:
379 */
380void irq_exit(void)
381{
382#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
383 local_irq_disable();
384#else
385 WARN_ON_ONCE(!irqs_disabled());
386#endif
387
388 account_irq_exit_time(current);
389 preempt_count_sub(HARDIRQ_OFFSET);
390 if (!in_interrupt() && local_softirq_pending())
391 invoke_softirq();
392
393 tick_irq_exit();
394 rcu_irq_exit();
395 trace_hardirq_exit(); /* must be last! */
396}
397
398/*
399 * This function must run with irqs disabled!
400 */
401inline void raise_softirq_irqoff(unsigned int nr)
402{
403 __raise_softirq_irqoff(nr);
404
405 /*
406 * If we're in an interrupt or softirq, we're done
407 * (this also catches softirq-disabled code). We will
408 * actually run the softirq once we return from
409 * the irq or softirq.
410 *
411 * Otherwise we wake up ksoftirqd to make sure we
412 * schedule the softirq soon.
413 */
414 if (!in_interrupt())
415 wakeup_softirqd();
416}
417
418void raise_softirq(unsigned int nr)
419{
420 unsigned long flags;
421
422 local_irq_save(flags);
423 raise_softirq_irqoff(nr);
424 local_irq_restore(flags);
425}
426
427void __raise_softirq_irqoff(unsigned int nr)
428{
429 trace_softirq_raise(nr);
430 or_softirq_pending(1UL << nr);
431}
432
433void open_softirq(int nr, void (*action)(struct softirq_action *))
434{
435 softirq_vec[nr].action = action;
436}
437
438/*
439 * Tasklets
440 */
441struct tasklet_head {
442 struct tasklet_struct *head;
443 struct tasklet_struct **tail;
444};
445
446static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
447static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
448
449void __tasklet_schedule(struct tasklet_struct *t)
450{
451 unsigned long flags;
452
453 local_irq_save(flags);
454 t->next = NULL;
455 *__this_cpu_read(tasklet_vec.tail) = t;
456 __this_cpu_write(tasklet_vec.tail, &(t->next));
457 raise_softirq_irqoff(TASKLET_SOFTIRQ);
458 local_irq_restore(flags);
459}
460EXPORT_SYMBOL(__tasklet_schedule);
461
462void __tasklet_hi_schedule(struct tasklet_struct *t)
463{
464 unsigned long flags;
465
466 local_irq_save(flags);
467 t->next = NULL;
468 *__this_cpu_read(tasklet_hi_vec.tail) = t;
469 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
470 raise_softirq_irqoff(HI_SOFTIRQ);
471 local_irq_restore(flags);
472}
473EXPORT_SYMBOL(__tasklet_hi_schedule);
474
475void __tasklet_hi_schedule_first(struct tasklet_struct *t)
476{
477 BUG_ON(!irqs_disabled());
478
479 t->next = __this_cpu_read(tasklet_hi_vec.head);
480 __this_cpu_write(tasklet_hi_vec.head, t);
481 __raise_softirq_irqoff(HI_SOFTIRQ);
482}
483EXPORT_SYMBOL(__tasklet_hi_schedule_first);
484
485static void tasklet_action(struct softirq_action *a)
486{
487 struct tasklet_struct *list;
488
489 local_irq_disable();
490 list = __this_cpu_read(tasklet_vec.head);
491 __this_cpu_write(tasklet_vec.head, NULL);
492 __this_cpu_write(tasklet_vec.tail, this_cpu_ptr(&tasklet_vec.head));
493 local_irq_enable();
494
495 while (list) {
496 struct tasklet_struct *t = list;
497
498 list = list->next;
499
500 if (tasklet_trylock(t)) {
501 if (!atomic_read(&t->count)) {
502 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
503 &t->state))
504 BUG();
505 t->func(t->data);
506 tasklet_unlock(t);
507 continue;
508 }
509 tasklet_unlock(t);
510 }
511
512 local_irq_disable();
513 t->next = NULL;
514 *__this_cpu_read(tasklet_vec.tail) = t;
515 __this_cpu_write(tasklet_vec.tail, &(t->next));
516 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
517 local_irq_enable();
518 }
519}
520
521static void tasklet_hi_action(struct softirq_action *a)
522{
523 struct tasklet_struct *list;
524
525 local_irq_disable();
526 list = __this_cpu_read(tasklet_hi_vec.head);
527 __this_cpu_write(tasklet_hi_vec.head, NULL);
528 __this_cpu_write(tasklet_hi_vec.tail, this_cpu_ptr(&tasklet_hi_vec.head));
529 local_irq_enable();
530
531 while (list) {
532 struct tasklet_struct *t = list;
533
534 list = list->next;
535
536 if (tasklet_trylock(t)) {
537 if (!atomic_read(&t->count)) {
538 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
539 &t->state))
540 BUG();
541 t->func(t->data);
542 tasklet_unlock(t);
543 continue;
544 }
545 tasklet_unlock(t);
546 }
547
548 local_irq_disable();
549 t->next = NULL;
550 *__this_cpu_read(tasklet_hi_vec.tail) = t;
551 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
552 __raise_softirq_irqoff(HI_SOFTIRQ);
553 local_irq_enable();
554 }
555}
556
557void tasklet_init(struct tasklet_struct *t,
558 void (*func)(unsigned long), unsigned long data)
559{
560 t->next = NULL;
561 t->state = 0;
562 atomic_set(&t->count, 0);
563 t->func = func;
564 t->data = data;
565}
566EXPORT_SYMBOL(tasklet_init);
567
568void tasklet_kill(struct tasklet_struct *t)
569{
570 if (in_interrupt())
571 pr_notice("Attempt to kill tasklet from interrupt\n");
572
573 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
574 do {
575 yield();
576 } while (test_bit(TASKLET_STATE_SCHED, &t->state));
577 }
578 tasklet_unlock_wait(t);
579 clear_bit(TASKLET_STATE_SCHED, &t->state);
580}
581EXPORT_SYMBOL(tasklet_kill);
582
583/*
584 * tasklet_hrtimer
585 */
586
587/*
588 * The trampoline is called when the hrtimer expires. It schedules a tasklet
589 * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
590 * hrtimer callback, but from softirq context.
591 */
592static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
593{
594 struct tasklet_hrtimer *ttimer =
595 container_of(timer, struct tasklet_hrtimer, timer);
596
597 tasklet_hi_schedule(&ttimer->tasklet);
598 return HRTIMER_NORESTART;
599}
600
601/*
602 * Helper function which calls the hrtimer callback from
603 * tasklet/softirq context
604 */
605static void __tasklet_hrtimer_trampoline(unsigned long data)
606{
607 struct tasklet_hrtimer *ttimer = (void *)data;
608 enum hrtimer_restart restart;
609
610 restart = ttimer->function(&ttimer->timer);
611 if (restart != HRTIMER_NORESTART)
612 hrtimer_restart(&ttimer->timer);
613}
614
615/**
616 * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
617 * @ttimer: tasklet_hrtimer which is initialized
618 * @function: hrtimer callback function which gets called from softirq context
619 * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
620 * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
621 */
622void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
623 enum hrtimer_restart (*function)(struct hrtimer *),
624 clockid_t which_clock, enum hrtimer_mode mode)
625{
626 hrtimer_init(&ttimer->timer, which_clock, mode);
627 ttimer->timer.function = __hrtimer_tasklet_trampoline;
628 tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
629 (unsigned long)ttimer);
630 ttimer->function = function;
631}
632EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
633
634void __init softirq_init(void)
635{
636 int cpu;
637
638 for_each_possible_cpu(cpu) {
639 per_cpu(tasklet_vec, cpu).tail =
640 &per_cpu(tasklet_vec, cpu).head;
641 per_cpu(tasklet_hi_vec, cpu).tail =
642 &per_cpu(tasklet_hi_vec, cpu).head;
643 }
644
645 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
646 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
647}
648
649static int ksoftirqd_should_run(unsigned int cpu)
650{
651 return local_softirq_pending();
652}
653
654static void run_ksoftirqd(unsigned int cpu)
655{
656 local_irq_disable();
657 if (local_softirq_pending()) {
658 /*
659 * We can safely run softirq on inline stack, as we are not deep
660 * in the task stack here.
661 */
662 __do_softirq();
663 local_irq_enable();
664 cond_resched_rcu_qs();
665 return;
666 }
667 local_irq_enable();
668}
669
670#ifdef CONFIG_HOTPLUG_CPU
671/*
672 * tasklet_kill_immediate is called to remove a tasklet which can already be
673 * scheduled for execution on @cpu.
674 *
675 * Unlike tasklet_kill, this function removes the tasklet
676 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
677 *
678 * When this function is called, @cpu must be in the CPU_DEAD state.
679 */
680void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
681{
682 struct tasklet_struct **i;
683
684 BUG_ON(cpu_online(cpu));
685 BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
686
687 if (!test_bit(TASKLET_STATE_SCHED, &t->state))
688 return;
689
690 /* CPU is dead, so no lock needed. */
691 for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
692 if (*i == t) {
693 *i = t->next;
694 /* If this was the tail element, move the tail ptr */
695 if (*i == NULL)
696 per_cpu(tasklet_vec, cpu).tail = i;
697 return;
698 }
699 }
700 BUG();
701}
702
703static void takeover_tasklets(unsigned int cpu)
704{
705 /* CPU is dead, so no lock needed. */
706 local_irq_disable();
707
708 /* Find end, append list for that CPU. */
709 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
710 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
711 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
712 per_cpu(tasklet_vec, cpu).head = NULL;
713 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
714 }
715 raise_softirq_irqoff(TASKLET_SOFTIRQ);
716
717 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
718 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
719 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
720 per_cpu(tasklet_hi_vec, cpu).head = NULL;
721 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
722 }
723 raise_softirq_irqoff(HI_SOFTIRQ);
724
725 local_irq_enable();
726}
727#endif /* CONFIG_HOTPLUG_CPU */
728
729static int cpu_callback(struct notifier_block *nfb, unsigned long action,
730 void *hcpu)
731{
732 switch (action) {
733#ifdef CONFIG_HOTPLUG_CPU
734 case CPU_DEAD:
735 case CPU_DEAD_FROZEN:
736 takeover_tasklets((unsigned long)hcpu);
737 break;
738#endif /* CONFIG_HOTPLUG_CPU */
739 }
740 return NOTIFY_OK;
741}
742
743static struct notifier_block cpu_nfb = {
744 .notifier_call = cpu_callback
745};
746
747static struct smp_hotplug_thread softirq_threads = {
748 .store = &ksoftirqd,
749 .thread_should_run = ksoftirqd_should_run,
750 .thread_fn = run_ksoftirqd,
751 .thread_comm = "ksoftirqd/%u",
752};
753
754static __init int spawn_ksoftirqd(void)
755{
756 register_cpu_notifier(&cpu_nfb);
757
758 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
759
760 return 0;
761}
762early_initcall(spawn_ksoftirqd);
763
764/*
765 * [ These __weak aliases are kept in a separate compilation unit, so that
766 * GCC does not inline them incorrectly. ]
767 */
768
769int __init __weak early_irq_init(void)
770{
771 return 0;
772}
773
774int __init __weak arch_probe_nr_irqs(void)
775{
776 return NR_IRQS_LEGACY;
777}
778
779int __init __weak arch_early_irq_init(void)
780{
781 return 0;
782}
783
784unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
785{
786 return from;
787}
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
31#include <asm/softirq_stack.h>
32
33#define CREATE_TRACE_POINTS
34#include <trace/events/irq.h>
35
36/*
37 - No shared variables, all the data are CPU local.
38 - If a softirq needs serialization, let it serialize itself
39 by its own spinlocks.
40 - Even if softirq is serialized, only local cpu is marked for
41 execution. Hence, we get something sort of weak cpu binding.
42 Though it is still not clear, will it result in better locality
43 or will not.
44
45 Examples:
46 - NET RX softirq. It is multithreaded and does not require
47 any global serialization.
48 - NET TX softirq. It kicks software netdevice queues, hence
49 it is logically serialized per device, but this serialization
50 is invisible to common code.
51 - Tasklets: serialized wrt itself.
52 */
53
54#ifndef __ARCH_IRQ_STAT
55DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat);
56EXPORT_PER_CPU_SYMBOL(irq_stat);
57#endif
58
59static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
60
61DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
62
63const char * const softirq_to_name[NR_SOFTIRQS] = {
64 "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL",
65 "TASKLET", "SCHED", "HRTIMER", "RCU"
66};
67
68/*
69 * we cannot loop indefinitely here to avoid userspace starvation,
70 * but we also don't want to introduce a worst case 1/HZ latency
71 * to the pending events, so lets the scheduler to balance
72 * the softirq load for us.
73 */
74static void wakeup_softirqd(void)
75{
76 /* Interrupts are disabled: no need to stop preemption */
77 struct task_struct *tsk = __this_cpu_read(ksoftirqd);
78
79 if (tsk)
80 wake_up_process(tsk);
81}
82
83/*
84 * If ksoftirqd is scheduled, we do not want to process pending softirqs
85 * right now. Let ksoftirqd handle this at its own rate, to get fairness,
86 * unless we're doing some of the synchronous softirqs.
87 */
88#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ))
89static bool ksoftirqd_running(unsigned long pending)
90{
91 struct task_struct *tsk = __this_cpu_read(ksoftirqd);
92
93 if (pending & SOFTIRQ_NOW_MASK)
94 return false;
95 return tsk && task_is_running(tsk) && !__kthread_should_park(tsk);
96}
97
98#ifdef CONFIG_TRACE_IRQFLAGS
99DEFINE_PER_CPU(int, hardirqs_enabled);
100DEFINE_PER_CPU(int, hardirq_context);
101EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled);
102EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context);
103#endif
104
105/*
106 * SOFTIRQ_OFFSET usage:
107 *
108 * On !RT kernels 'count' is the preempt counter, on RT kernels this applies
109 * to a per CPU counter and to task::softirqs_disabled_cnt.
110 *
111 * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq
112 * processing.
113 *
114 * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
115 * on local_bh_disable or local_bh_enable.
116 *
117 * This lets us distinguish between whether we are currently processing
118 * softirq and whether we just have bh disabled.
119 */
120#ifdef CONFIG_PREEMPT_RT
121
122/*
123 * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and
124 * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a
125 * softirq disabled section to be preempted.
126 *
127 * The per task counter is used for softirq_count(), in_softirq() and
128 * in_serving_softirqs() because these counts are only valid when the task
129 * holding softirq_ctrl::lock is running.
130 *
131 * The per CPU counter prevents pointless wakeups of ksoftirqd in case that
132 * the task which is in a softirq disabled section is preempted or blocks.
133 */
134struct softirq_ctrl {
135 local_lock_t lock;
136 int cnt;
137};
138
139static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = {
140 .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock),
141};
142
143/**
144 * local_bh_blocked() - Check for idle whether BH processing is blocked
145 *
146 * Returns false if the per CPU softirq::cnt is 0 otherwise true.
147 *
148 * This is invoked from the idle task to guard against false positive
149 * softirq pending warnings, which would happen when the task which holds
150 * softirq_ctrl::lock was the only running task on the CPU and blocks on
151 * some other lock.
152 */
153bool local_bh_blocked(void)
154{
155 return __this_cpu_read(softirq_ctrl.cnt) != 0;
156}
157
158void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
159{
160 unsigned long flags;
161 int newcnt;
162
163 WARN_ON_ONCE(in_hardirq());
164
165 /* First entry of a task into a BH disabled section? */
166 if (!current->softirq_disable_cnt) {
167 if (preemptible()) {
168 local_lock(&softirq_ctrl.lock);
169 /* Required to meet the RCU bottomhalf requirements. */
170 rcu_read_lock();
171 } else {
172 DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt));
173 }
174 }
175
176 /*
177 * Track the per CPU softirq disabled state. On RT this is per CPU
178 * state to allow preemption of bottom half disabled sections.
179 */
180 newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt);
181 /*
182 * Reflect the result in the task state to prevent recursion on the
183 * local lock and to make softirq_count() & al work.
184 */
185 current->softirq_disable_cnt = newcnt;
186
187 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) {
188 raw_local_irq_save(flags);
189 lockdep_softirqs_off(ip);
190 raw_local_irq_restore(flags);
191 }
192}
193EXPORT_SYMBOL(__local_bh_disable_ip);
194
195static void __local_bh_enable(unsigned int cnt, bool unlock)
196{
197 unsigned long flags;
198 int newcnt;
199
200 DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=
201 this_cpu_read(softirq_ctrl.cnt));
202
203 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) {
204 raw_local_irq_save(flags);
205 lockdep_softirqs_on(_RET_IP_);
206 raw_local_irq_restore(flags);
207 }
208
209 newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt);
210 current->softirq_disable_cnt = newcnt;
211
212 if (!newcnt && unlock) {
213 rcu_read_unlock();
214 local_unlock(&softirq_ctrl.lock);
215 }
216}
217
218void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
219{
220 bool preempt_on = preemptible();
221 unsigned long flags;
222 u32 pending;
223 int curcnt;
224
225 WARN_ON_ONCE(in_hardirq());
226 lockdep_assert_irqs_enabled();
227
228 local_irq_save(flags);
229 curcnt = __this_cpu_read(softirq_ctrl.cnt);
230
231 /*
232 * If this is not reenabling soft interrupts, no point in trying to
233 * run pending ones.
234 */
235 if (curcnt != cnt)
236 goto out;
237
238 pending = local_softirq_pending();
239 if (!pending || ksoftirqd_running(pending))
240 goto out;
241
242 /*
243 * If this was called from non preemptible context, wake up the
244 * softirq daemon.
245 */
246 if (!preempt_on) {
247 wakeup_softirqd();
248 goto out;
249 }
250
251 /*
252 * Adjust softirq count to SOFTIRQ_OFFSET which makes
253 * in_serving_softirq() become true.
254 */
255 cnt = SOFTIRQ_OFFSET;
256 __local_bh_enable(cnt, false);
257 __do_softirq();
258
259out:
260 __local_bh_enable(cnt, preempt_on);
261 local_irq_restore(flags);
262}
263EXPORT_SYMBOL(__local_bh_enable_ip);
264
265/*
266 * Invoked from ksoftirqd_run() outside of the interrupt disabled section
267 * to acquire the per CPU local lock for reentrancy protection.
268 */
269static inline void ksoftirqd_run_begin(void)
270{
271 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
272 local_irq_disable();
273}
274
275/* Counterpart to ksoftirqd_run_begin() */
276static inline void ksoftirqd_run_end(void)
277{
278 __local_bh_enable(SOFTIRQ_OFFSET, true);
279 WARN_ON_ONCE(in_interrupt());
280 local_irq_enable();
281}
282
283static inline void softirq_handle_begin(void) { }
284static inline void softirq_handle_end(void) { }
285
286static inline bool should_wake_ksoftirqd(void)
287{
288 return !this_cpu_read(softirq_ctrl.cnt);
289}
290
291static inline void invoke_softirq(void)
292{
293 if (should_wake_ksoftirqd())
294 wakeup_softirqd();
295}
296
297/*
298 * flush_smp_call_function_queue() can raise a soft interrupt in a function
299 * call. On RT kernels this is undesired and the only known functionality
300 * in the block layer which does this is disabled on RT. If soft interrupts
301 * get raised which haven't been raised before the flush, warn so it can be
302 * investigated.
303 */
304void do_softirq_post_smp_call_flush(unsigned int was_pending)
305{
306 if (WARN_ON_ONCE(was_pending != local_softirq_pending()))
307 invoke_softirq();
308}
309
310#else /* CONFIG_PREEMPT_RT */
311
312/*
313 * This one is for softirq.c-internal use, where hardirqs are disabled
314 * legitimately:
315 */
316#ifdef CONFIG_TRACE_IRQFLAGS
317void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
318{
319 unsigned long flags;
320
321 WARN_ON_ONCE(in_hardirq());
322
323 raw_local_irq_save(flags);
324 /*
325 * The preempt tracer hooks into preempt_count_add and will break
326 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
327 * is set and before current->softirq_enabled is cleared.
328 * We must manually increment preempt_count here and manually
329 * call the trace_preempt_off later.
330 */
331 __preempt_count_add(cnt);
332 /*
333 * Were softirqs turned off above:
334 */
335 if (softirq_count() == (cnt & SOFTIRQ_MASK))
336 lockdep_softirqs_off(ip);
337 raw_local_irq_restore(flags);
338
339 if (preempt_count() == cnt) {
340#ifdef CONFIG_DEBUG_PREEMPT
341 current->preempt_disable_ip = get_lock_parent_ip();
342#endif
343 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
344 }
345}
346EXPORT_SYMBOL(__local_bh_disable_ip);
347#endif /* CONFIG_TRACE_IRQFLAGS */
348
349static void __local_bh_enable(unsigned int cnt)
350{
351 lockdep_assert_irqs_disabled();
352
353 if (preempt_count() == cnt)
354 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
355
356 if (softirq_count() == (cnt & SOFTIRQ_MASK))
357 lockdep_softirqs_on(_RET_IP_);
358
359 __preempt_count_sub(cnt);
360}
361
362/*
363 * Special-case - softirqs can safely be enabled by __do_softirq(),
364 * without processing still-pending softirqs:
365 */
366void _local_bh_enable(void)
367{
368 WARN_ON_ONCE(in_hardirq());
369 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
370}
371EXPORT_SYMBOL(_local_bh_enable);
372
373void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
374{
375 WARN_ON_ONCE(in_hardirq());
376 lockdep_assert_irqs_enabled();
377#ifdef CONFIG_TRACE_IRQFLAGS
378 local_irq_disable();
379#endif
380 /*
381 * Are softirqs going to be turned on now:
382 */
383 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
384 lockdep_softirqs_on(ip);
385 /*
386 * Keep preemption disabled until we are done with
387 * softirq processing:
388 */
389 __preempt_count_sub(cnt - 1);
390
391 if (unlikely(!in_interrupt() && local_softirq_pending())) {
392 /*
393 * Run softirq if any pending. And do it in its own stack
394 * as we may be calling this deep in a task call stack already.
395 */
396 do_softirq();
397 }
398
399 preempt_count_dec();
400#ifdef CONFIG_TRACE_IRQFLAGS
401 local_irq_enable();
402#endif
403 preempt_check_resched();
404}
405EXPORT_SYMBOL(__local_bh_enable_ip);
406
407static inline void softirq_handle_begin(void)
408{
409 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
410}
411
412static inline void softirq_handle_end(void)
413{
414 __local_bh_enable(SOFTIRQ_OFFSET);
415 WARN_ON_ONCE(in_interrupt());
416}
417
418static inline void ksoftirqd_run_begin(void)
419{
420 local_irq_disable();
421}
422
423static inline void ksoftirqd_run_end(void)
424{
425 local_irq_enable();
426}
427
428static inline bool should_wake_ksoftirqd(void)
429{
430 return true;
431}
432
433static inline void invoke_softirq(void)
434{
435 if (ksoftirqd_running(local_softirq_pending()))
436 return;
437
438 if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
439#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
440 /*
441 * We can safely execute softirq on the current stack if
442 * it is the irq stack, because it should be near empty
443 * at this stage.
444 */
445 __do_softirq();
446#else
447 /*
448 * Otherwise, irq_exit() is called on the task stack that can
449 * be potentially deep already. So call softirq in its own stack
450 * to prevent from any overrun.
451 */
452 do_softirq_own_stack();
453#endif
454 } else {
455 wakeup_softirqd();
456 }
457}
458
459asmlinkage __visible void do_softirq(void)
460{
461 __u32 pending;
462 unsigned long flags;
463
464 if (in_interrupt())
465 return;
466
467 local_irq_save(flags);
468
469 pending = local_softirq_pending();
470
471 if (pending && !ksoftirqd_running(pending))
472 do_softirq_own_stack();
473
474 local_irq_restore(flags);
475}
476
477#endif /* !CONFIG_PREEMPT_RT */
478
479/*
480 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
481 * but break the loop if need_resched() is set or after 2 ms.
482 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
483 * certain cases, such as stop_machine(), jiffies may cease to
484 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
485 * well to make sure we eventually return from this method.
486 *
487 * These limits have been established via experimentation.
488 * The two things to balance is latency against fairness -
489 * we want to handle softirqs as soon as possible, but they
490 * should not be able to lock up the box.
491 */
492#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
493#define MAX_SOFTIRQ_RESTART 10
494
495#ifdef CONFIG_TRACE_IRQFLAGS
496/*
497 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
498 * to keep the lockdep irq context tracking as tight as possible in order to
499 * not miss-qualify lock contexts and miss possible deadlocks.
500 */
501
502static inline bool lockdep_softirq_start(void)
503{
504 bool in_hardirq = false;
505
506 if (lockdep_hardirq_context()) {
507 in_hardirq = true;
508 lockdep_hardirq_exit();
509 }
510
511 lockdep_softirq_enter();
512
513 return in_hardirq;
514}
515
516static inline void lockdep_softirq_end(bool in_hardirq)
517{
518 lockdep_softirq_exit();
519
520 if (in_hardirq)
521 lockdep_hardirq_enter();
522}
523#else
524static inline bool lockdep_softirq_start(void) { return false; }
525static inline void lockdep_softirq_end(bool in_hardirq) { }
526#endif
527
528asmlinkage __visible void __softirq_entry __do_softirq(void)
529{
530 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
531 unsigned long old_flags = current->flags;
532 int max_restart = MAX_SOFTIRQ_RESTART;
533 struct softirq_action *h;
534 bool in_hardirq;
535 __u32 pending;
536 int softirq_bit;
537
538 /*
539 * Mask out PF_MEMALLOC as the current task context is borrowed for the
540 * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
541 * again if the socket is related to swapping.
542 */
543 current->flags &= ~PF_MEMALLOC;
544
545 pending = local_softirq_pending();
546
547 softirq_handle_begin();
548 in_hardirq = lockdep_softirq_start();
549 account_softirq_enter(current);
550
551restart:
552 /* Reset the pending bitmask before enabling irqs */
553 set_softirq_pending(0);
554
555 local_irq_enable();
556
557 h = softirq_vec;
558
559 while ((softirq_bit = ffs(pending))) {
560 unsigned int vec_nr;
561 int prev_count;
562
563 h += softirq_bit - 1;
564
565 vec_nr = h - softirq_vec;
566 prev_count = preempt_count();
567
568 kstat_incr_softirqs_this_cpu(vec_nr);
569
570 trace_softirq_entry(vec_nr);
571 h->action(h);
572 trace_softirq_exit(vec_nr);
573 if (unlikely(prev_count != preempt_count())) {
574 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
575 vec_nr, softirq_to_name[vec_nr], h->action,
576 prev_count, preempt_count());
577 preempt_count_set(prev_count);
578 }
579 h++;
580 pending >>= softirq_bit;
581 }
582
583 if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
584 __this_cpu_read(ksoftirqd) == current)
585 rcu_softirq_qs();
586
587 local_irq_disable();
588
589 pending = local_softirq_pending();
590 if (pending) {
591 if (time_before(jiffies, end) && !need_resched() &&
592 --max_restart)
593 goto restart;
594
595 wakeup_softirqd();
596 }
597
598 account_softirq_exit(current);
599 lockdep_softirq_end(in_hardirq);
600 softirq_handle_end();
601 current_restore_flags(old_flags, PF_MEMALLOC);
602}
603
604/**
605 * irq_enter_rcu - Enter an interrupt context with RCU watching
606 */
607void irq_enter_rcu(void)
608{
609 __irq_enter_raw();
610
611 if (tick_nohz_full_cpu(smp_processor_id()) ||
612 (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)))
613 tick_irq_enter();
614
615 account_hardirq_enter(current);
616}
617
618/**
619 * irq_enter - Enter an interrupt context including RCU update
620 */
621void irq_enter(void)
622{
623 ct_irq_enter();
624 irq_enter_rcu();
625}
626
627static inline void tick_irq_exit(void)
628{
629#ifdef CONFIG_NO_HZ_COMMON
630 int cpu = smp_processor_id();
631
632 /* Make sure that timer wheel updates are propagated */
633 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
634 if (!in_hardirq())
635 tick_nohz_irq_exit();
636 }
637#endif
638}
639
640static inline void __irq_exit_rcu(void)
641{
642#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
643 local_irq_disable();
644#else
645 lockdep_assert_irqs_disabled();
646#endif
647 account_hardirq_exit(current);
648 preempt_count_sub(HARDIRQ_OFFSET);
649 if (!in_interrupt() && local_softirq_pending())
650 invoke_softirq();
651
652 tick_irq_exit();
653}
654
655/**
656 * irq_exit_rcu() - Exit an interrupt context without updating RCU
657 *
658 * Also processes softirqs if needed and possible.
659 */
660void irq_exit_rcu(void)
661{
662 __irq_exit_rcu();
663 /* must be last! */
664 lockdep_hardirq_exit();
665}
666
667/**
668 * irq_exit - Exit an interrupt context, update RCU and lockdep
669 *
670 * Also processes softirqs if needed and possible.
671 */
672void irq_exit(void)
673{
674 __irq_exit_rcu();
675 ct_irq_exit();
676 /* must be last! */
677 lockdep_hardirq_exit();
678}
679
680/*
681 * This function must run with irqs disabled!
682 */
683inline void raise_softirq_irqoff(unsigned int nr)
684{
685 __raise_softirq_irqoff(nr);
686
687 /*
688 * If we're in an interrupt or softirq, we're done
689 * (this also catches softirq-disabled code). We will
690 * actually run the softirq once we return from
691 * the irq or softirq.
692 *
693 * Otherwise we wake up ksoftirqd to make sure we
694 * schedule the softirq soon.
695 */
696 if (!in_interrupt() && should_wake_ksoftirqd())
697 wakeup_softirqd();
698}
699
700void raise_softirq(unsigned int nr)
701{
702 unsigned long flags;
703
704 local_irq_save(flags);
705 raise_softirq_irqoff(nr);
706 local_irq_restore(flags);
707}
708
709void __raise_softirq_irqoff(unsigned int nr)
710{
711 lockdep_assert_irqs_disabled();
712 trace_softirq_raise(nr);
713 or_softirq_pending(1UL << nr);
714}
715
716void open_softirq(int nr, void (*action)(struct softirq_action *))
717{
718 softirq_vec[nr].action = action;
719}
720
721/*
722 * Tasklets
723 */
724struct tasklet_head {
725 struct tasklet_struct *head;
726 struct tasklet_struct **tail;
727};
728
729static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
730static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
731
732static void __tasklet_schedule_common(struct tasklet_struct *t,
733 struct tasklet_head __percpu *headp,
734 unsigned int softirq_nr)
735{
736 struct tasklet_head *head;
737 unsigned long flags;
738
739 local_irq_save(flags);
740 head = this_cpu_ptr(headp);
741 t->next = NULL;
742 *head->tail = t;
743 head->tail = &(t->next);
744 raise_softirq_irqoff(softirq_nr);
745 local_irq_restore(flags);
746}
747
748void __tasklet_schedule(struct tasklet_struct *t)
749{
750 __tasklet_schedule_common(t, &tasklet_vec,
751 TASKLET_SOFTIRQ);
752}
753EXPORT_SYMBOL(__tasklet_schedule);
754
755void __tasklet_hi_schedule(struct tasklet_struct *t)
756{
757 __tasklet_schedule_common(t, &tasklet_hi_vec,
758 HI_SOFTIRQ);
759}
760EXPORT_SYMBOL(__tasklet_hi_schedule);
761
762static bool tasklet_clear_sched(struct tasklet_struct *t)
763{
764 if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
765 wake_up_var(&t->state);
766 return true;
767 }
768
769 WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
770 t->use_callback ? "callback" : "func",
771 t->use_callback ? (void *)t->callback : (void *)t->func);
772
773 return false;
774}
775
776static void tasklet_action_common(struct softirq_action *a,
777 struct tasklet_head *tl_head,
778 unsigned int softirq_nr)
779{
780 struct tasklet_struct *list;
781
782 local_irq_disable();
783 list = tl_head->head;
784 tl_head->head = NULL;
785 tl_head->tail = &tl_head->head;
786 local_irq_enable();
787
788 while (list) {
789 struct tasklet_struct *t = list;
790
791 list = list->next;
792
793 if (tasklet_trylock(t)) {
794 if (!atomic_read(&t->count)) {
795 if (tasklet_clear_sched(t)) {
796 if (t->use_callback)
797 t->callback(t);
798 else
799 t->func(t->data);
800 }
801 tasklet_unlock(t);
802 continue;
803 }
804 tasklet_unlock(t);
805 }
806
807 local_irq_disable();
808 t->next = NULL;
809 *tl_head->tail = t;
810 tl_head->tail = &t->next;
811 __raise_softirq_irqoff(softirq_nr);
812 local_irq_enable();
813 }
814}
815
816static __latent_entropy void tasklet_action(struct softirq_action *a)
817{
818 tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
819}
820
821static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
822{
823 tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
824}
825
826void tasklet_setup(struct tasklet_struct *t,
827 void (*callback)(struct tasklet_struct *))
828{
829 t->next = NULL;
830 t->state = 0;
831 atomic_set(&t->count, 0);
832 t->callback = callback;
833 t->use_callback = true;
834 t->data = 0;
835}
836EXPORT_SYMBOL(tasklet_setup);
837
838void tasklet_init(struct tasklet_struct *t,
839 void (*func)(unsigned long), unsigned long data)
840{
841 t->next = NULL;
842 t->state = 0;
843 atomic_set(&t->count, 0);
844 t->func = func;
845 t->use_callback = false;
846 t->data = data;
847}
848EXPORT_SYMBOL(tasklet_init);
849
850#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
851/*
852 * Do not use in new code. Waiting for tasklets from atomic contexts is
853 * error prone and should be avoided.
854 */
855void tasklet_unlock_spin_wait(struct tasklet_struct *t)
856{
857 while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
858 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
859 /*
860 * Prevent a live lock when current preempted soft
861 * interrupt processing or prevents ksoftirqd from
862 * running. If the tasklet runs on a different CPU
863 * then this has no effect other than doing the BH
864 * disable/enable dance for nothing.
865 */
866 local_bh_disable();
867 local_bh_enable();
868 } else {
869 cpu_relax();
870 }
871 }
872}
873EXPORT_SYMBOL(tasklet_unlock_spin_wait);
874#endif
875
876void tasklet_kill(struct tasklet_struct *t)
877{
878 if (in_interrupt())
879 pr_notice("Attempt to kill tasklet from interrupt\n");
880
881 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
882 wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
883
884 tasklet_unlock_wait(t);
885 tasklet_clear_sched(t);
886}
887EXPORT_SYMBOL(tasklet_kill);
888
889#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
890void tasklet_unlock(struct tasklet_struct *t)
891{
892 smp_mb__before_atomic();
893 clear_bit(TASKLET_STATE_RUN, &t->state);
894 smp_mb__after_atomic();
895 wake_up_var(&t->state);
896}
897EXPORT_SYMBOL_GPL(tasklet_unlock);
898
899void tasklet_unlock_wait(struct tasklet_struct *t)
900{
901 wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
902}
903EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
904#endif
905
906void __init softirq_init(void)
907{
908 int cpu;
909
910 for_each_possible_cpu(cpu) {
911 per_cpu(tasklet_vec, cpu).tail =
912 &per_cpu(tasklet_vec, cpu).head;
913 per_cpu(tasklet_hi_vec, cpu).tail =
914 &per_cpu(tasklet_hi_vec, cpu).head;
915 }
916
917 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
918 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
919}
920
921static int ksoftirqd_should_run(unsigned int cpu)
922{
923 return local_softirq_pending();
924}
925
926static void run_ksoftirqd(unsigned int cpu)
927{
928 ksoftirqd_run_begin();
929 if (local_softirq_pending()) {
930 /*
931 * We can safely run softirq on inline stack, as we are not deep
932 * in the task stack here.
933 */
934 __do_softirq();
935 ksoftirqd_run_end();
936 cond_resched();
937 return;
938 }
939 ksoftirqd_run_end();
940}
941
942#ifdef CONFIG_HOTPLUG_CPU
943static int takeover_tasklets(unsigned int cpu)
944{
945 /* CPU is dead, so no lock needed. */
946 local_irq_disable();
947
948 /* Find end, append list for that CPU. */
949 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
950 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
951 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
952 per_cpu(tasklet_vec, cpu).head = NULL;
953 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
954 }
955 raise_softirq_irqoff(TASKLET_SOFTIRQ);
956
957 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
958 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
959 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
960 per_cpu(tasklet_hi_vec, cpu).head = NULL;
961 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
962 }
963 raise_softirq_irqoff(HI_SOFTIRQ);
964
965 local_irq_enable();
966 return 0;
967}
968#else
969#define takeover_tasklets NULL
970#endif /* CONFIG_HOTPLUG_CPU */
971
972static struct smp_hotplug_thread softirq_threads = {
973 .store = &ksoftirqd,
974 .thread_should_run = ksoftirqd_should_run,
975 .thread_fn = run_ksoftirqd,
976 .thread_comm = "ksoftirqd/%u",
977};
978
979static __init int spawn_ksoftirqd(void)
980{
981 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
982 takeover_tasklets);
983 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
984
985 return 0;
986}
987early_initcall(spawn_ksoftirqd);
988
989/*
990 * [ These __weak aliases are kept in a separate compilation unit, so that
991 * GCC does not inline them incorrectly. ]
992 */
993
994int __init __weak early_irq_init(void)
995{
996 return 0;
997}
998
999int __init __weak arch_probe_nr_irqs(void)
1000{
1001 return NR_IRQS_LEGACY;
1002}
1003
1004int __init __weak arch_early_irq_init(void)
1005{
1006 return 0;
1007}
1008
1009unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
1010{
1011 return from;
1012}