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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}
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_irq());
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#else /* CONFIG_PREEMPT_RT */
298
299/*
300 * This one is for softirq.c-internal use, where hardirqs are disabled
301 * legitimately:
302 */
303#ifdef CONFIG_TRACE_IRQFLAGS
304void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
305{
306 unsigned long flags;
307
308 WARN_ON_ONCE(in_irq());
309
310 raw_local_irq_save(flags);
311 /*
312 * The preempt tracer hooks into preempt_count_add and will break
313 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
314 * is set and before current->softirq_enabled is cleared.
315 * We must manually increment preempt_count here and manually
316 * call the trace_preempt_off later.
317 */
318 __preempt_count_add(cnt);
319 /*
320 * Were softirqs turned off above:
321 */
322 if (softirq_count() == (cnt & SOFTIRQ_MASK))
323 lockdep_softirqs_off(ip);
324 raw_local_irq_restore(flags);
325
326 if (preempt_count() == cnt) {
327#ifdef CONFIG_DEBUG_PREEMPT
328 current->preempt_disable_ip = get_lock_parent_ip();
329#endif
330 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
331 }
332}
333EXPORT_SYMBOL(__local_bh_disable_ip);
334#endif /* CONFIG_TRACE_IRQFLAGS */
335
336static void __local_bh_enable(unsigned int cnt)
337{
338 lockdep_assert_irqs_disabled();
339
340 if (preempt_count() == cnt)
341 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
342
343 if (softirq_count() == (cnt & SOFTIRQ_MASK))
344 lockdep_softirqs_on(_RET_IP_);
345
346 __preempt_count_sub(cnt);
347}
348
349/*
350 * Special-case - softirqs can safely be enabled by __do_softirq(),
351 * without processing still-pending softirqs:
352 */
353void _local_bh_enable(void)
354{
355 WARN_ON_ONCE(in_irq());
356 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
357}
358EXPORT_SYMBOL(_local_bh_enable);
359
360void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
361{
362 WARN_ON_ONCE(in_irq());
363 lockdep_assert_irqs_enabled();
364#ifdef CONFIG_TRACE_IRQFLAGS
365 local_irq_disable();
366#endif
367 /*
368 * Are softirqs going to be turned on now:
369 */
370 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
371 lockdep_softirqs_on(ip);
372 /*
373 * Keep preemption disabled until we are done with
374 * softirq processing:
375 */
376 __preempt_count_sub(cnt - 1);
377
378 if (unlikely(!in_interrupt() && local_softirq_pending())) {
379 /*
380 * Run softirq if any pending. And do it in its own stack
381 * as we may be calling this deep in a task call stack already.
382 */
383 do_softirq();
384 }
385
386 preempt_count_dec();
387#ifdef CONFIG_TRACE_IRQFLAGS
388 local_irq_enable();
389#endif
390 preempt_check_resched();
391}
392EXPORT_SYMBOL(__local_bh_enable_ip);
393
394static inline void softirq_handle_begin(void)
395{
396 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
397}
398
399static inline void softirq_handle_end(void)
400{
401 __local_bh_enable(SOFTIRQ_OFFSET);
402 WARN_ON_ONCE(in_interrupt());
403}
404
405static inline void ksoftirqd_run_begin(void)
406{
407 local_irq_disable();
408}
409
410static inline void ksoftirqd_run_end(void)
411{
412 local_irq_enable();
413}
414
415static inline bool should_wake_ksoftirqd(void)
416{
417 return true;
418}
419
420static inline void invoke_softirq(void)
421{
422 if (ksoftirqd_running(local_softirq_pending()))
423 return;
424
425 if (!force_irqthreads || !__this_cpu_read(ksoftirqd)) {
426#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
427 /*
428 * We can safely execute softirq on the current stack if
429 * it is the irq stack, because it should be near empty
430 * at this stage.
431 */
432 __do_softirq();
433#else
434 /*
435 * Otherwise, irq_exit() is called on the task stack that can
436 * be potentially deep already. So call softirq in its own stack
437 * to prevent from any overrun.
438 */
439 do_softirq_own_stack();
440#endif
441 } else {
442 wakeup_softirqd();
443 }
444}
445
446asmlinkage __visible void do_softirq(void)
447{
448 __u32 pending;
449 unsigned long flags;
450
451 if (in_interrupt())
452 return;
453
454 local_irq_save(flags);
455
456 pending = local_softirq_pending();
457
458 if (pending && !ksoftirqd_running(pending))
459 do_softirq_own_stack();
460
461 local_irq_restore(flags);
462}
463
464#endif /* !CONFIG_PREEMPT_RT */
465
466/*
467 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
468 * but break the loop if need_resched() is set or after 2 ms.
469 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
470 * certain cases, such as stop_machine(), jiffies may cease to
471 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
472 * well to make sure we eventually return from this method.
473 *
474 * These limits have been established via experimentation.
475 * The two things to balance is latency against fairness -
476 * we want to handle softirqs as soon as possible, but they
477 * should not be able to lock up the box.
478 */
479#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
480#define MAX_SOFTIRQ_RESTART 10
481
482#ifdef CONFIG_TRACE_IRQFLAGS
483/*
484 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
485 * to keep the lockdep irq context tracking as tight as possible in order to
486 * not miss-qualify lock contexts and miss possible deadlocks.
487 */
488
489static inline bool lockdep_softirq_start(void)
490{
491 bool in_hardirq = false;
492
493 if (lockdep_hardirq_context()) {
494 in_hardirq = true;
495 lockdep_hardirq_exit();
496 }
497
498 lockdep_softirq_enter();
499
500 return in_hardirq;
501}
502
503static inline void lockdep_softirq_end(bool in_hardirq)
504{
505 lockdep_softirq_exit();
506
507 if (in_hardirq)
508 lockdep_hardirq_enter();
509}
510#else
511static inline bool lockdep_softirq_start(void) { return false; }
512static inline void lockdep_softirq_end(bool in_hardirq) { }
513#endif
514
515asmlinkage __visible void __softirq_entry __do_softirq(void)
516{
517 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
518 unsigned long old_flags = current->flags;
519 int max_restart = MAX_SOFTIRQ_RESTART;
520 struct softirq_action *h;
521 bool in_hardirq;
522 __u32 pending;
523 int softirq_bit;
524
525 /*
526 * Mask out PF_MEMALLOC as the current task context is borrowed for the
527 * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
528 * again if the socket is related to swapping.
529 */
530 current->flags &= ~PF_MEMALLOC;
531
532 pending = local_softirq_pending();
533
534 softirq_handle_begin();
535 in_hardirq = lockdep_softirq_start();
536 account_softirq_enter(current);
537
538restart:
539 /* Reset the pending bitmask before enabling irqs */
540 set_softirq_pending(0);
541
542 local_irq_enable();
543
544 h = softirq_vec;
545
546 while ((softirq_bit = ffs(pending))) {
547 unsigned int vec_nr;
548 int prev_count;
549
550 h += softirq_bit - 1;
551
552 vec_nr = h - softirq_vec;
553 prev_count = preempt_count();
554
555 kstat_incr_softirqs_this_cpu(vec_nr);
556
557 trace_softirq_entry(vec_nr);
558 h->action(h);
559 trace_softirq_exit(vec_nr);
560 if (unlikely(prev_count != preempt_count())) {
561 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
562 vec_nr, softirq_to_name[vec_nr], h->action,
563 prev_count, preempt_count());
564 preempt_count_set(prev_count);
565 }
566 h++;
567 pending >>= softirq_bit;
568 }
569
570 if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
571 __this_cpu_read(ksoftirqd) == current)
572 rcu_softirq_qs();
573
574 local_irq_disable();
575
576 pending = local_softirq_pending();
577 if (pending) {
578 if (time_before(jiffies, end) && !need_resched() &&
579 --max_restart)
580 goto restart;
581
582 wakeup_softirqd();
583 }
584
585 account_softirq_exit(current);
586 lockdep_softirq_end(in_hardirq);
587 softirq_handle_end();
588 current_restore_flags(old_flags, PF_MEMALLOC);
589}
590
591/**
592 * irq_enter_rcu - Enter an interrupt context with RCU watching
593 */
594void irq_enter_rcu(void)
595{
596 __irq_enter_raw();
597
598 if (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET))
599 tick_irq_enter();
600
601 account_hardirq_enter(current);
602}
603
604/**
605 * irq_enter - Enter an interrupt context including RCU update
606 */
607void irq_enter(void)
608{
609 rcu_irq_enter();
610 irq_enter_rcu();
611}
612
613static inline void tick_irq_exit(void)
614{
615#ifdef CONFIG_NO_HZ_COMMON
616 int cpu = smp_processor_id();
617
618 /* Make sure that timer wheel updates are propagated */
619 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
620 if (!in_irq())
621 tick_nohz_irq_exit();
622 }
623#endif
624}
625
626static inline void __irq_exit_rcu(void)
627{
628#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
629 local_irq_disable();
630#else
631 lockdep_assert_irqs_disabled();
632#endif
633 account_hardirq_exit(current);
634 preempt_count_sub(HARDIRQ_OFFSET);
635 if (!in_interrupt() && local_softirq_pending())
636 invoke_softirq();
637
638 tick_irq_exit();
639}
640
641/**
642 * irq_exit_rcu() - Exit an interrupt context without updating RCU
643 *
644 * Also processes softirqs if needed and possible.
645 */
646void irq_exit_rcu(void)
647{
648 __irq_exit_rcu();
649 /* must be last! */
650 lockdep_hardirq_exit();
651}
652
653/**
654 * irq_exit - Exit an interrupt context, update RCU and lockdep
655 *
656 * Also processes softirqs if needed and possible.
657 */
658void irq_exit(void)
659{
660 __irq_exit_rcu();
661 rcu_irq_exit();
662 /* must be last! */
663 lockdep_hardirq_exit();
664}
665
666/*
667 * This function must run with irqs disabled!
668 */
669inline void raise_softirq_irqoff(unsigned int nr)
670{
671 __raise_softirq_irqoff(nr);
672
673 /*
674 * If we're in an interrupt or softirq, we're done
675 * (this also catches softirq-disabled code). We will
676 * actually run the softirq once we return from
677 * the irq or softirq.
678 *
679 * Otherwise we wake up ksoftirqd to make sure we
680 * schedule the softirq soon.
681 */
682 if (!in_interrupt() && should_wake_ksoftirqd())
683 wakeup_softirqd();
684}
685
686void raise_softirq(unsigned int nr)
687{
688 unsigned long flags;
689
690 local_irq_save(flags);
691 raise_softirq_irqoff(nr);
692 local_irq_restore(flags);
693}
694
695void __raise_softirq_irqoff(unsigned int nr)
696{
697 lockdep_assert_irqs_disabled();
698 trace_softirq_raise(nr);
699 or_softirq_pending(1UL << nr);
700}
701
702void open_softirq(int nr, void (*action)(struct softirq_action *))
703{
704 softirq_vec[nr].action = action;
705}
706
707/*
708 * Tasklets
709 */
710struct tasklet_head {
711 struct tasklet_struct *head;
712 struct tasklet_struct **tail;
713};
714
715static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
716static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
717
718static void __tasklet_schedule_common(struct tasklet_struct *t,
719 struct tasklet_head __percpu *headp,
720 unsigned int softirq_nr)
721{
722 struct tasklet_head *head;
723 unsigned long flags;
724
725 local_irq_save(flags);
726 head = this_cpu_ptr(headp);
727 t->next = NULL;
728 *head->tail = t;
729 head->tail = &(t->next);
730 raise_softirq_irqoff(softirq_nr);
731 local_irq_restore(flags);
732}
733
734void __tasklet_schedule(struct tasklet_struct *t)
735{
736 __tasklet_schedule_common(t, &tasklet_vec,
737 TASKLET_SOFTIRQ);
738}
739EXPORT_SYMBOL(__tasklet_schedule);
740
741void __tasklet_hi_schedule(struct tasklet_struct *t)
742{
743 __tasklet_schedule_common(t, &tasklet_hi_vec,
744 HI_SOFTIRQ);
745}
746EXPORT_SYMBOL(__tasklet_hi_schedule);
747
748static bool tasklet_clear_sched(struct tasklet_struct *t)
749{
750 if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
751 wake_up_var(&t->state);
752 return true;
753 }
754
755 WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
756 t->use_callback ? "callback" : "func",
757 t->use_callback ? (void *)t->callback : (void *)t->func);
758
759 return false;
760}
761
762static void tasklet_action_common(struct softirq_action *a,
763 struct tasklet_head *tl_head,
764 unsigned int softirq_nr)
765{
766 struct tasklet_struct *list;
767
768 local_irq_disable();
769 list = tl_head->head;
770 tl_head->head = NULL;
771 tl_head->tail = &tl_head->head;
772 local_irq_enable();
773
774 while (list) {
775 struct tasklet_struct *t = list;
776
777 list = list->next;
778
779 if (tasklet_trylock(t)) {
780 if (!atomic_read(&t->count)) {
781 if (tasklet_clear_sched(t)) {
782 if (t->use_callback)
783 t->callback(t);
784 else
785 t->func(t->data);
786 }
787 tasklet_unlock(t);
788 continue;
789 }
790 tasklet_unlock(t);
791 }
792
793 local_irq_disable();
794 t->next = NULL;
795 *tl_head->tail = t;
796 tl_head->tail = &t->next;
797 __raise_softirq_irqoff(softirq_nr);
798 local_irq_enable();
799 }
800}
801
802static __latent_entropy void tasklet_action(struct softirq_action *a)
803{
804 tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
805}
806
807static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
808{
809 tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
810}
811
812void tasklet_setup(struct tasklet_struct *t,
813 void (*callback)(struct tasklet_struct *))
814{
815 t->next = NULL;
816 t->state = 0;
817 atomic_set(&t->count, 0);
818 t->callback = callback;
819 t->use_callback = true;
820 t->data = 0;
821}
822EXPORT_SYMBOL(tasklet_setup);
823
824void tasklet_init(struct tasklet_struct *t,
825 void (*func)(unsigned long), unsigned long data)
826{
827 t->next = NULL;
828 t->state = 0;
829 atomic_set(&t->count, 0);
830 t->func = func;
831 t->use_callback = false;
832 t->data = data;
833}
834EXPORT_SYMBOL(tasklet_init);
835
836#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
837/*
838 * Do not use in new code. Waiting for tasklets from atomic contexts is
839 * error prone and should be avoided.
840 */
841void tasklet_unlock_spin_wait(struct tasklet_struct *t)
842{
843 while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
844 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
845 /*
846 * Prevent a live lock when current preempted soft
847 * interrupt processing or prevents ksoftirqd from
848 * running. If the tasklet runs on a different CPU
849 * then this has no effect other than doing the BH
850 * disable/enable dance for nothing.
851 */
852 local_bh_disable();
853 local_bh_enable();
854 } else {
855 cpu_relax();
856 }
857 }
858}
859EXPORT_SYMBOL(tasklet_unlock_spin_wait);
860#endif
861
862void tasklet_kill(struct tasklet_struct *t)
863{
864 if (in_interrupt())
865 pr_notice("Attempt to kill tasklet from interrupt\n");
866
867 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
868 wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
869
870 tasklet_unlock_wait(t);
871 tasklet_clear_sched(t);
872}
873EXPORT_SYMBOL(tasklet_kill);
874
875#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
876void tasklet_unlock(struct tasklet_struct *t)
877{
878 smp_mb__before_atomic();
879 clear_bit(TASKLET_STATE_RUN, &t->state);
880 smp_mb__after_atomic();
881 wake_up_var(&t->state);
882}
883EXPORT_SYMBOL_GPL(tasklet_unlock);
884
885void tasklet_unlock_wait(struct tasklet_struct *t)
886{
887 wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
888}
889EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
890#endif
891
892void __init softirq_init(void)
893{
894 int cpu;
895
896 for_each_possible_cpu(cpu) {
897 per_cpu(tasklet_vec, cpu).tail =
898 &per_cpu(tasklet_vec, cpu).head;
899 per_cpu(tasklet_hi_vec, cpu).tail =
900 &per_cpu(tasklet_hi_vec, cpu).head;
901 }
902
903 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
904 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
905}
906
907static int ksoftirqd_should_run(unsigned int cpu)
908{
909 return local_softirq_pending();
910}
911
912static void run_ksoftirqd(unsigned int cpu)
913{
914 ksoftirqd_run_begin();
915 if (local_softirq_pending()) {
916 /*
917 * We can safely run softirq on inline stack, as we are not deep
918 * in the task stack here.
919 */
920 __do_softirq();
921 ksoftirqd_run_end();
922 cond_resched();
923 return;
924 }
925 ksoftirqd_run_end();
926}
927
928#ifdef CONFIG_HOTPLUG_CPU
929static int takeover_tasklets(unsigned int cpu)
930{
931 /* CPU is dead, so no lock needed. */
932 local_irq_disable();
933
934 /* Find end, append list for that CPU. */
935 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
936 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
937 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
938 per_cpu(tasklet_vec, cpu).head = NULL;
939 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
940 }
941 raise_softirq_irqoff(TASKLET_SOFTIRQ);
942
943 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
944 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
945 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
946 per_cpu(tasklet_hi_vec, cpu).head = NULL;
947 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
948 }
949 raise_softirq_irqoff(HI_SOFTIRQ);
950
951 local_irq_enable();
952 return 0;
953}
954#else
955#define takeover_tasklets NULL
956#endif /* CONFIG_HOTPLUG_CPU */
957
958static struct smp_hotplug_thread softirq_threads = {
959 .store = &ksoftirqd,
960 .thread_should_run = ksoftirqd_should_run,
961 .thread_fn = run_ksoftirqd,
962 .thread_comm = "ksoftirqd/%u",
963};
964
965static __init int spawn_ksoftirqd(void)
966{
967 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
968 takeover_tasklets);
969 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
970
971 return 0;
972}
973early_initcall(spawn_ksoftirqd);
974
975/*
976 * [ These __weak aliases are kept in a separate compilation unit, so that
977 * GCC does not inline them incorrectly. ]
978 */
979
980int __init __weak early_irq_init(void)
981{
982 return 0;
983}
984
985int __init __weak arch_probe_nr_irqs(void)
986{
987 return NR_IRQS_LEGACY;
988}
989
990int __init __weak arch_early_irq_init(void)
991{
992 return 0;
993}
994
995unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
996{
997 return from;
998}