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1/*
2 * linux/kernel/softirq.c
3 *
4 * Copyright (C) 1992 Linus Torvalds
5 *
6 * Distribute under GPLv2.
7 *
8 * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/export.h>
14#include <linux/kernel_stat.h>
15#include <linux/interrupt.h>
16#include <linux/init.h>
17#include <linux/mm.h>
18#include <linux/notifier.h>
19#include <linux/percpu.h>
20#include <linux/cpu.h>
21#include <linux/freezer.h>
22#include <linux/kthread.h>
23#include <linux/rcupdate.h>
24#include <linux/ftrace.h>
25#include <linux/smp.h>
26#include <linux/smpboot.h>
27#include <linux/tick.h>
28#include <linux/irq.h>
29
30#define CREATE_TRACE_POINTS
31#include <trace/events/irq.h>
32
33/*
34 - No shared variables, all the data are CPU local.
35 - If a softirq needs serialization, let it serialize itself
36 by its own spinlocks.
37 - Even if softirq is serialized, only local cpu is marked for
38 execution. Hence, we get something sort of weak cpu binding.
39 Though it is still not clear, will it result in better locality
40 or will not.
41
42 Examples:
43 - NET RX softirq. It is multithreaded and does not require
44 any global serialization.
45 - NET TX softirq. It kicks software netdevice queues, hence
46 it is logically serialized per device, but this serialization
47 is invisible to common code.
48 - Tasklets: serialized wrt itself.
49 */
50
51#ifndef __ARCH_IRQ_STAT
52irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
53EXPORT_SYMBOL(irq_stat);
54#endif
55
56static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
57
58DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
59
60const char * const softirq_to_name[NR_SOFTIRQS] = {
61 "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL",
62 "TASKLET", "SCHED", "HRTIMER", "RCU"
63};
64
65/*
66 * we cannot loop indefinitely here to avoid userspace starvation,
67 * but we also don't want to introduce a worst case 1/HZ latency
68 * to the pending events, so lets the scheduler to balance
69 * the softirq load for us.
70 */
71static void wakeup_softirqd(void)
72{
73 /* Interrupts are disabled: no need to stop preemption */
74 struct task_struct *tsk = __this_cpu_read(ksoftirqd);
75
76 if (tsk && tsk->state != TASK_RUNNING)
77 wake_up_process(tsk);
78}
79
80/*
81 * If ksoftirqd is scheduled, we do not want to process pending softirqs
82 * right now. Let ksoftirqd handle this at its own rate, to get fairness.
83 */
84static bool ksoftirqd_running(void)
85{
86 struct task_struct *tsk = __this_cpu_read(ksoftirqd);
87
88 return tsk && (tsk->state == TASK_RUNNING);
89}
90
91/*
92 * preempt_count and SOFTIRQ_OFFSET usage:
93 * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
94 * softirq processing.
95 * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
96 * on local_bh_disable or local_bh_enable.
97 * This lets us distinguish between whether we are currently processing
98 * softirq and whether we just have bh disabled.
99 */
100
101/*
102 * This one is for softirq.c-internal use,
103 * where hardirqs are disabled legitimately:
104 */
105#ifdef CONFIG_TRACE_IRQFLAGS
106void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
107{
108 unsigned long flags;
109
110 WARN_ON_ONCE(in_irq());
111
112 raw_local_irq_save(flags);
113 /*
114 * The preempt tracer hooks into preempt_count_add and will break
115 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
116 * is set and before current->softirq_enabled is cleared.
117 * We must manually increment preempt_count here and manually
118 * call the trace_preempt_off later.
119 */
120 __preempt_count_add(cnt);
121 /*
122 * Were softirqs turned off above:
123 */
124 if (softirq_count() == (cnt & SOFTIRQ_MASK))
125 trace_softirqs_off(ip);
126 raw_local_irq_restore(flags);
127
128 if (preempt_count() == cnt) {
129#ifdef CONFIG_DEBUG_PREEMPT
130 current->preempt_disable_ip = get_lock_parent_ip();
131#endif
132 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
133 }
134}
135EXPORT_SYMBOL(__local_bh_disable_ip);
136#endif /* CONFIG_TRACE_IRQFLAGS */
137
138static void __local_bh_enable(unsigned int cnt)
139{
140 WARN_ON_ONCE(!irqs_disabled());
141
142 if (softirq_count() == (cnt & SOFTIRQ_MASK))
143 trace_softirqs_on(_RET_IP_);
144 preempt_count_sub(cnt);
145}
146
147/*
148 * Special-case - softirqs can safely be enabled in
149 * cond_resched_softirq(), or by __do_softirq(),
150 * without processing still-pending softirqs:
151 */
152void _local_bh_enable(void)
153{
154 WARN_ON_ONCE(in_irq());
155 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
156}
157EXPORT_SYMBOL(_local_bh_enable);
158
159void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
160{
161 WARN_ON_ONCE(in_irq() || irqs_disabled());
162#ifdef CONFIG_TRACE_IRQFLAGS
163 local_irq_disable();
164#endif
165 /*
166 * Are softirqs going to be turned on now:
167 */
168 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
169 trace_softirqs_on(ip);
170 /*
171 * Keep preemption disabled until we are done with
172 * softirq processing:
173 */
174 preempt_count_sub(cnt - 1);
175
176 if (unlikely(!in_interrupt() && local_softirq_pending())) {
177 /*
178 * Run softirq if any pending. And do it in its own stack
179 * as we may be calling this deep in a task call stack already.
180 */
181 do_softirq();
182 }
183
184 preempt_count_dec();
185#ifdef CONFIG_TRACE_IRQFLAGS
186 local_irq_enable();
187#endif
188 preempt_check_resched();
189}
190EXPORT_SYMBOL(__local_bh_enable_ip);
191
192/*
193 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
194 * but break the loop if need_resched() is set or after 2 ms.
195 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
196 * certain cases, such as stop_machine(), jiffies may cease to
197 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
198 * well to make sure we eventually return from this method.
199 *
200 * These limits have been established via experimentation.
201 * The two things to balance is latency against fairness -
202 * we want to handle softirqs as soon as possible, but they
203 * should not be able to lock up the box.
204 */
205#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
206#define MAX_SOFTIRQ_RESTART 10
207
208#ifdef CONFIG_TRACE_IRQFLAGS
209/*
210 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
211 * to keep the lockdep irq context tracking as tight as possible in order to
212 * not miss-qualify lock contexts and miss possible deadlocks.
213 */
214
215static inline bool lockdep_softirq_start(void)
216{
217 bool in_hardirq = false;
218
219 if (trace_hardirq_context(current)) {
220 in_hardirq = true;
221 trace_hardirq_exit();
222 }
223
224 lockdep_softirq_enter();
225
226 return in_hardirq;
227}
228
229static inline void lockdep_softirq_end(bool in_hardirq)
230{
231 lockdep_softirq_exit();
232
233 if (in_hardirq)
234 trace_hardirq_enter();
235}
236#else
237static inline bool lockdep_softirq_start(void) { return false; }
238static inline void lockdep_softirq_end(bool in_hardirq) { }
239#endif
240
241asmlinkage __visible void __softirq_entry __do_softirq(void)
242{
243 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
244 unsigned long old_flags = current->flags;
245 int max_restart = MAX_SOFTIRQ_RESTART;
246 struct softirq_action *h;
247 bool in_hardirq;
248 __u32 pending;
249 int softirq_bit;
250
251 /*
252 * Mask out PF_MEMALLOC s current task context is borrowed for the
253 * softirq. A softirq handled such as network RX might set PF_MEMALLOC
254 * again if the socket is related to swap
255 */
256 current->flags &= ~PF_MEMALLOC;
257
258 pending = local_softirq_pending();
259 account_irq_enter_time(current);
260
261 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
262 in_hardirq = lockdep_softirq_start();
263
264restart:
265 /* Reset the pending bitmask before enabling irqs */
266 set_softirq_pending(0);
267
268 local_irq_enable();
269
270 h = softirq_vec;
271
272 while ((softirq_bit = ffs(pending))) {
273 unsigned int vec_nr;
274 int prev_count;
275
276 h += softirq_bit - 1;
277
278 vec_nr = h - softirq_vec;
279 prev_count = preempt_count();
280
281 kstat_incr_softirqs_this_cpu(vec_nr);
282
283 trace_softirq_entry(vec_nr);
284 h->action(h);
285 trace_softirq_exit(vec_nr);
286 if (unlikely(prev_count != preempt_count())) {
287 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
288 vec_nr, softirq_to_name[vec_nr], h->action,
289 prev_count, preempt_count());
290 preempt_count_set(prev_count);
291 }
292 h++;
293 pending >>= softirq_bit;
294 }
295
296 rcu_bh_qs();
297 local_irq_disable();
298
299 pending = local_softirq_pending();
300 if (pending) {
301 if (time_before(jiffies, end) && !need_resched() &&
302 --max_restart)
303 goto restart;
304
305 wakeup_softirqd();
306 }
307
308 lockdep_softirq_end(in_hardirq);
309 account_irq_exit_time(current);
310 __local_bh_enable(SOFTIRQ_OFFSET);
311 WARN_ON_ONCE(in_interrupt());
312 tsk_restore_flags(current, old_flags, PF_MEMALLOC);
313}
314
315asmlinkage __visible void do_softirq(void)
316{
317 __u32 pending;
318 unsigned long flags;
319
320 if (in_interrupt())
321 return;
322
323 local_irq_save(flags);
324
325 pending = local_softirq_pending();
326
327 if (pending && !ksoftirqd_running())
328 do_softirq_own_stack();
329
330 local_irq_restore(flags);
331}
332
333/*
334 * Enter an interrupt context.
335 */
336void irq_enter(void)
337{
338 rcu_irq_enter();
339 if (is_idle_task(current) && !in_interrupt()) {
340 /*
341 * Prevent raise_softirq from needlessly waking up ksoftirqd
342 * here, as softirq will be serviced on return from interrupt.
343 */
344 local_bh_disable();
345 tick_irq_enter();
346 _local_bh_enable();
347 }
348
349 __irq_enter();
350}
351
352static inline void invoke_softirq(void)
353{
354 if (ksoftirqd_running())
355 return;
356
357 if (!force_irqthreads) {
358#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
359 /*
360 * We can safely execute softirq on the current stack if
361 * it is the irq stack, because it should be near empty
362 * at this stage.
363 */
364 __do_softirq();
365#else
366 /*
367 * Otherwise, irq_exit() is called on the task stack that can
368 * be potentially deep already. So call softirq in its own stack
369 * to prevent from any overrun.
370 */
371 do_softirq_own_stack();
372#endif
373 } else {
374 wakeup_softirqd();
375 }
376}
377
378static inline void tick_irq_exit(void)
379{
380#ifdef CONFIG_NO_HZ_COMMON
381 int cpu = smp_processor_id();
382
383 /* Make sure that timer wheel updates are propagated */
384 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
385 if (!in_interrupt())
386 tick_nohz_irq_exit();
387 }
388#endif
389}
390
391/*
392 * Exit an interrupt context. Process softirqs if needed and possible:
393 */
394void irq_exit(void)
395{
396#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
397 local_irq_disable();
398#else
399 WARN_ON_ONCE(!irqs_disabled());
400#endif
401
402 account_irq_exit_time(current);
403 preempt_count_sub(HARDIRQ_OFFSET);
404 if (!in_interrupt() && local_softirq_pending())
405 invoke_softirq();
406
407 tick_irq_exit();
408 rcu_irq_exit();
409 trace_hardirq_exit(); /* must be last! */
410}
411
412/*
413 * This function must run with irqs disabled!
414 */
415inline void raise_softirq_irqoff(unsigned int nr)
416{
417 __raise_softirq_irqoff(nr);
418
419 /*
420 * If we're in an interrupt or softirq, we're done
421 * (this also catches softirq-disabled code). We will
422 * actually run the softirq once we return from
423 * the irq or softirq.
424 *
425 * Otherwise we wake up ksoftirqd to make sure we
426 * schedule the softirq soon.
427 */
428 if (!in_interrupt())
429 wakeup_softirqd();
430}
431
432void raise_softirq(unsigned int nr)
433{
434 unsigned long flags;
435
436 local_irq_save(flags);
437 raise_softirq_irqoff(nr);
438 local_irq_restore(flags);
439}
440
441void __raise_softirq_irqoff(unsigned int nr)
442{
443 trace_softirq_raise(nr);
444 or_softirq_pending(1UL << nr);
445}
446
447void open_softirq(int nr, void (*action)(struct softirq_action *))
448{
449 softirq_vec[nr].action = action;
450}
451
452/*
453 * Tasklets
454 */
455struct tasklet_head {
456 struct tasklet_struct *head;
457 struct tasklet_struct **tail;
458};
459
460static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
461static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
462
463void __tasklet_schedule(struct tasklet_struct *t)
464{
465 unsigned long flags;
466
467 local_irq_save(flags);
468 t->next = NULL;
469 *__this_cpu_read(tasklet_vec.tail) = t;
470 __this_cpu_write(tasklet_vec.tail, &(t->next));
471 raise_softirq_irqoff(TASKLET_SOFTIRQ);
472 local_irq_restore(flags);
473}
474EXPORT_SYMBOL(__tasklet_schedule);
475
476void __tasklet_hi_schedule(struct tasklet_struct *t)
477{
478 unsigned long flags;
479
480 local_irq_save(flags);
481 t->next = NULL;
482 *__this_cpu_read(tasklet_hi_vec.tail) = t;
483 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
484 raise_softirq_irqoff(HI_SOFTIRQ);
485 local_irq_restore(flags);
486}
487EXPORT_SYMBOL(__tasklet_hi_schedule);
488
489void __tasklet_hi_schedule_first(struct tasklet_struct *t)
490{
491 BUG_ON(!irqs_disabled());
492
493 t->next = __this_cpu_read(tasklet_hi_vec.head);
494 __this_cpu_write(tasklet_hi_vec.head, t);
495 __raise_softirq_irqoff(HI_SOFTIRQ);
496}
497EXPORT_SYMBOL(__tasklet_hi_schedule_first);
498
499static __latent_entropy void tasklet_action(struct softirq_action *a)
500{
501 struct tasklet_struct *list;
502
503 local_irq_disable();
504 list = __this_cpu_read(tasklet_vec.head);
505 __this_cpu_write(tasklet_vec.head, NULL);
506 __this_cpu_write(tasklet_vec.tail, this_cpu_ptr(&tasklet_vec.head));
507 local_irq_enable();
508
509 while (list) {
510 struct tasklet_struct *t = list;
511
512 list = list->next;
513
514 if (tasklet_trylock(t)) {
515 if (!atomic_read(&t->count)) {
516 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
517 &t->state))
518 BUG();
519 t->func(t->data);
520 tasklet_unlock(t);
521 continue;
522 }
523 tasklet_unlock(t);
524 }
525
526 local_irq_disable();
527 t->next = NULL;
528 *__this_cpu_read(tasklet_vec.tail) = t;
529 __this_cpu_write(tasklet_vec.tail, &(t->next));
530 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
531 local_irq_enable();
532 }
533}
534
535static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
536{
537 struct tasklet_struct *list;
538
539 local_irq_disable();
540 list = __this_cpu_read(tasklet_hi_vec.head);
541 __this_cpu_write(tasklet_hi_vec.head, NULL);
542 __this_cpu_write(tasklet_hi_vec.tail, this_cpu_ptr(&tasklet_hi_vec.head));
543 local_irq_enable();
544
545 while (list) {
546 struct tasklet_struct *t = list;
547
548 list = list->next;
549
550 if (tasklet_trylock(t)) {
551 if (!atomic_read(&t->count)) {
552 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
553 &t->state))
554 BUG();
555 t->func(t->data);
556 tasklet_unlock(t);
557 continue;
558 }
559 tasklet_unlock(t);
560 }
561
562 local_irq_disable();
563 t->next = NULL;
564 *__this_cpu_read(tasklet_hi_vec.tail) = t;
565 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
566 __raise_softirq_irqoff(HI_SOFTIRQ);
567 local_irq_enable();
568 }
569}
570
571void tasklet_init(struct tasklet_struct *t,
572 void (*func)(unsigned long), unsigned long data)
573{
574 t->next = NULL;
575 t->state = 0;
576 atomic_set(&t->count, 0);
577 t->func = func;
578 t->data = data;
579}
580EXPORT_SYMBOL(tasklet_init);
581
582void tasklet_kill(struct tasklet_struct *t)
583{
584 if (in_interrupt())
585 pr_notice("Attempt to kill tasklet from interrupt\n");
586
587 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
588 do {
589 yield();
590 } while (test_bit(TASKLET_STATE_SCHED, &t->state));
591 }
592 tasklet_unlock_wait(t);
593 clear_bit(TASKLET_STATE_SCHED, &t->state);
594}
595EXPORT_SYMBOL(tasklet_kill);
596
597/*
598 * tasklet_hrtimer
599 */
600
601/*
602 * The trampoline is called when the hrtimer expires. It schedules a tasklet
603 * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
604 * hrtimer callback, but from softirq context.
605 */
606static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
607{
608 struct tasklet_hrtimer *ttimer =
609 container_of(timer, struct tasklet_hrtimer, timer);
610
611 tasklet_hi_schedule(&ttimer->tasklet);
612 return HRTIMER_NORESTART;
613}
614
615/*
616 * Helper function which calls the hrtimer callback from
617 * tasklet/softirq context
618 */
619static void __tasklet_hrtimer_trampoline(unsigned long data)
620{
621 struct tasklet_hrtimer *ttimer = (void *)data;
622 enum hrtimer_restart restart;
623
624 restart = ttimer->function(&ttimer->timer);
625 if (restart != HRTIMER_NORESTART)
626 hrtimer_restart(&ttimer->timer);
627}
628
629/**
630 * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
631 * @ttimer: tasklet_hrtimer which is initialized
632 * @function: hrtimer callback function which gets called from softirq context
633 * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
634 * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
635 */
636void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
637 enum hrtimer_restart (*function)(struct hrtimer *),
638 clockid_t which_clock, enum hrtimer_mode mode)
639{
640 hrtimer_init(&ttimer->timer, which_clock, mode);
641 ttimer->timer.function = __hrtimer_tasklet_trampoline;
642 tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
643 (unsigned long)ttimer);
644 ttimer->function = function;
645}
646EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
647
648void __init softirq_init(void)
649{
650 int cpu;
651
652 for_each_possible_cpu(cpu) {
653 per_cpu(tasklet_vec, cpu).tail =
654 &per_cpu(tasklet_vec, cpu).head;
655 per_cpu(tasklet_hi_vec, cpu).tail =
656 &per_cpu(tasklet_hi_vec, cpu).head;
657 }
658
659 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
660 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
661}
662
663static int ksoftirqd_should_run(unsigned int cpu)
664{
665 return local_softirq_pending();
666}
667
668static void run_ksoftirqd(unsigned int cpu)
669{
670 local_irq_disable();
671 if (local_softirq_pending()) {
672 /*
673 * We can safely run softirq on inline stack, as we are not deep
674 * in the task stack here.
675 */
676 __do_softirq();
677 local_irq_enable();
678 cond_resched_rcu_qs();
679 return;
680 }
681 local_irq_enable();
682}
683
684#ifdef CONFIG_HOTPLUG_CPU
685/*
686 * tasklet_kill_immediate is called to remove a tasklet which can already be
687 * scheduled for execution on @cpu.
688 *
689 * Unlike tasklet_kill, this function removes the tasklet
690 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
691 *
692 * When this function is called, @cpu must be in the CPU_DEAD state.
693 */
694void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
695{
696 struct tasklet_struct **i;
697
698 BUG_ON(cpu_online(cpu));
699 BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
700
701 if (!test_bit(TASKLET_STATE_SCHED, &t->state))
702 return;
703
704 /* CPU is dead, so no lock needed. */
705 for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
706 if (*i == t) {
707 *i = t->next;
708 /* If this was the tail element, move the tail ptr */
709 if (*i == NULL)
710 per_cpu(tasklet_vec, cpu).tail = i;
711 return;
712 }
713 }
714 BUG();
715}
716
717static int takeover_tasklets(unsigned int cpu)
718{
719 /* CPU is dead, so no lock needed. */
720 local_irq_disable();
721
722 /* Find end, append list for that CPU. */
723 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
724 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
725 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
726 per_cpu(tasklet_vec, cpu).head = NULL;
727 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
728 }
729 raise_softirq_irqoff(TASKLET_SOFTIRQ);
730
731 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
732 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
733 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
734 per_cpu(tasklet_hi_vec, cpu).head = NULL;
735 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
736 }
737 raise_softirq_irqoff(HI_SOFTIRQ);
738
739 local_irq_enable();
740 return 0;
741}
742#else
743#define takeover_tasklets NULL
744#endif /* CONFIG_HOTPLUG_CPU */
745
746static struct smp_hotplug_thread softirq_threads = {
747 .store = &ksoftirqd,
748 .thread_should_run = ksoftirqd_should_run,
749 .thread_fn = run_ksoftirqd,
750 .thread_comm = "ksoftirqd/%u",
751};
752
753static __init int spawn_ksoftirqd(void)
754{
755 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
756 takeover_tasklets);
757 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
758
759 return 0;
760}
761early_initcall(spawn_ksoftirqd);
762
763/*
764 * [ These __weak aliases are kept in a separate compilation unit, so that
765 * GCC does not inline them incorrectly. ]
766 */
767
768int __init __weak early_irq_init(void)
769{
770 return 0;
771}
772
773int __init __weak arch_probe_nr_irqs(void)
774{
775 return NR_IRQS_LEGACY;
776}
777
778int __init __weak arch_early_irq_init(void)
779{
780 return 0;
781}
782
783unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
784{
785 return from;
786}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/softirq.c
4 *
5 * Copyright (C) 1992 Linus Torvalds
6 *
7 * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
8 */
9
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12#include <linux/export.h>
13#include <linux/kernel_stat.h>
14#include <linux/interrupt.h>
15#include <linux/init.h>
16#include <linux/local_lock.h>
17#include <linux/mm.h>
18#include <linux/notifier.h>
19#include <linux/percpu.h>
20#include <linux/cpu.h>
21#include <linux/freezer.h>
22#include <linux/kthread.h>
23#include <linux/rcupdate.h>
24#include <linux/ftrace.h>
25#include <linux/smp.h>
26#include <linux/smpboot.h>
27#include <linux/tick.h>
28#include <linux/irq.h>
29#include <linux/wait_bit.h>
30#include <linux/workqueue.h>
31
32#include <asm/softirq_stack.h>
33
34#define CREATE_TRACE_POINTS
35#include <trace/events/irq.h>
36
37/*
38 - No shared variables, all the data are CPU local.
39 - If a softirq needs serialization, let it serialize itself
40 by its own spinlocks.
41 - Even if softirq is serialized, only local cpu is marked for
42 execution. Hence, we get something sort of weak cpu binding.
43 Though it is still not clear, will it result in better locality
44 or will not.
45
46 Examples:
47 - NET RX softirq. It is multithreaded and does not require
48 any global serialization.
49 - NET TX softirq. It kicks software netdevice queues, hence
50 it is logically serialized per device, but this serialization
51 is invisible to common code.
52 - Tasklets: serialized wrt itself.
53 */
54
55#ifndef __ARCH_IRQ_STAT
56DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat);
57EXPORT_PER_CPU_SYMBOL(irq_stat);
58#endif
59
60static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
61
62DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
63
64const char * const softirq_to_name[NR_SOFTIRQS] = {
65 "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL",
66 "TASKLET", "SCHED", "HRTIMER", "RCU"
67};
68
69/*
70 * we cannot loop indefinitely here to avoid userspace starvation,
71 * but we also don't want to introduce a worst case 1/HZ latency
72 * to the pending events, so lets the scheduler to balance
73 * the softirq load for us.
74 */
75static void wakeup_softirqd(void)
76{
77 /* Interrupts are disabled: no need to stop preemption */
78 struct task_struct *tsk = __this_cpu_read(ksoftirqd);
79
80 if (tsk)
81 wake_up_process(tsk);
82}
83
84#ifdef CONFIG_TRACE_IRQFLAGS
85DEFINE_PER_CPU(int, hardirqs_enabled);
86DEFINE_PER_CPU(int, hardirq_context);
87EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled);
88EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context);
89#endif
90
91/*
92 * SOFTIRQ_OFFSET usage:
93 *
94 * On !RT kernels 'count' is the preempt counter, on RT kernels this applies
95 * to a per CPU counter and to task::softirqs_disabled_cnt.
96 *
97 * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq
98 * processing.
99 *
100 * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
101 * on local_bh_disable or local_bh_enable.
102 *
103 * This lets us distinguish between whether we are currently processing
104 * softirq and whether we just have bh disabled.
105 */
106#ifdef CONFIG_PREEMPT_RT
107
108/*
109 * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and
110 * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a
111 * softirq disabled section to be preempted.
112 *
113 * The per task counter is used for softirq_count(), in_softirq() and
114 * in_serving_softirqs() because these counts are only valid when the task
115 * holding softirq_ctrl::lock is running.
116 *
117 * The per CPU counter prevents pointless wakeups of ksoftirqd in case that
118 * the task which is in a softirq disabled section is preempted or blocks.
119 */
120struct softirq_ctrl {
121 local_lock_t lock;
122 int cnt;
123};
124
125static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = {
126 .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock),
127};
128
129/**
130 * local_bh_blocked() - Check for idle whether BH processing is blocked
131 *
132 * Returns false if the per CPU softirq::cnt is 0 otherwise true.
133 *
134 * This is invoked from the idle task to guard against false positive
135 * softirq pending warnings, which would happen when the task which holds
136 * softirq_ctrl::lock was the only running task on the CPU and blocks on
137 * some other lock.
138 */
139bool local_bh_blocked(void)
140{
141 return __this_cpu_read(softirq_ctrl.cnt) != 0;
142}
143
144void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
145{
146 unsigned long flags;
147 int newcnt;
148
149 WARN_ON_ONCE(in_hardirq());
150
151 /* First entry of a task into a BH disabled section? */
152 if (!current->softirq_disable_cnt) {
153 if (preemptible()) {
154 local_lock(&softirq_ctrl.lock);
155 /* Required to meet the RCU bottomhalf requirements. */
156 rcu_read_lock();
157 } else {
158 DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt));
159 }
160 }
161
162 /*
163 * Track the per CPU softirq disabled state. On RT this is per CPU
164 * state to allow preemption of bottom half disabled sections.
165 */
166 newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt);
167 /*
168 * Reflect the result in the task state to prevent recursion on the
169 * local lock and to make softirq_count() & al work.
170 */
171 current->softirq_disable_cnt = newcnt;
172
173 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) {
174 raw_local_irq_save(flags);
175 lockdep_softirqs_off(ip);
176 raw_local_irq_restore(flags);
177 }
178}
179EXPORT_SYMBOL(__local_bh_disable_ip);
180
181static void __local_bh_enable(unsigned int cnt, bool unlock)
182{
183 unsigned long flags;
184 int newcnt;
185
186 DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=
187 this_cpu_read(softirq_ctrl.cnt));
188
189 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) {
190 raw_local_irq_save(flags);
191 lockdep_softirqs_on(_RET_IP_);
192 raw_local_irq_restore(flags);
193 }
194
195 newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt);
196 current->softirq_disable_cnt = newcnt;
197
198 if (!newcnt && unlock) {
199 rcu_read_unlock();
200 local_unlock(&softirq_ctrl.lock);
201 }
202}
203
204void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
205{
206 bool preempt_on = preemptible();
207 unsigned long flags;
208 u32 pending;
209 int curcnt;
210
211 WARN_ON_ONCE(in_hardirq());
212 lockdep_assert_irqs_enabled();
213
214 local_irq_save(flags);
215 curcnt = __this_cpu_read(softirq_ctrl.cnt);
216
217 /*
218 * If this is not reenabling soft interrupts, no point in trying to
219 * run pending ones.
220 */
221 if (curcnt != cnt)
222 goto out;
223
224 pending = local_softirq_pending();
225 if (!pending)
226 goto out;
227
228 /*
229 * If this was called from non preemptible context, wake up the
230 * softirq daemon.
231 */
232 if (!preempt_on) {
233 wakeup_softirqd();
234 goto out;
235 }
236
237 /*
238 * Adjust softirq count to SOFTIRQ_OFFSET which makes
239 * in_serving_softirq() become true.
240 */
241 cnt = SOFTIRQ_OFFSET;
242 __local_bh_enable(cnt, false);
243 __do_softirq();
244
245out:
246 __local_bh_enable(cnt, preempt_on);
247 local_irq_restore(flags);
248}
249EXPORT_SYMBOL(__local_bh_enable_ip);
250
251/*
252 * Invoked from ksoftirqd_run() outside of the interrupt disabled section
253 * to acquire the per CPU local lock for reentrancy protection.
254 */
255static inline void ksoftirqd_run_begin(void)
256{
257 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
258 local_irq_disable();
259}
260
261/* Counterpart to ksoftirqd_run_begin() */
262static inline void ksoftirqd_run_end(void)
263{
264 __local_bh_enable(SOFTIRQ_OFFSET, true);
265 WARN_ON_ONCE(in_interrupt());
266 local_irq_enable();
267}
268
269static inline void softirq_handle_begin(void) { }
270static inline void softirq_handle_end(void) { }
271
272static inline bool should_wake_ksoftirqd(void)
273{
274 return !this_cpu_read(softirq_ctrl.cnt);
275}
276
277static inline void invoke_softirq(void)
278{
279 if (should_wake_ksoftirqd())
280 wakeup_softirqd();
281}
282
283#define SCHED_SOFTIRQ_MASK BIT(SCHED_SOFTIRQ)
284
285/*
286 * flush_smp_call_function_queue() can raise a soft interrupt in a function
287 * call. On RT kernels this is undesired and the only known functionalities
288 * are in the block layer which is disabled on RT, and in the scheduler for
289 * idle load balancing. If soft interrupts get raised which haven't been
290 * raised before the flush, warn if it is not a SCHED_SOFTIRQ so it can be
291 * investigated.
292 */
293void do_softirq_post_smp_call_flush(unsigned int was_pending)
294{
295 unsigned int is_pending = local_softirq_pending();
296
297 if (unlikely(was_pending != is_pending)) {
298 WARN_ON_ONCE(was_pending != (is_pending & ~SCHED_SOFTIRQ_MASK));
299 invoke_softirq();
300 }
301}
302
303#else /* CONFIG_PREEMPT_RT */
304
305/*
306 * This one is for softirq.c-internal use, where hardirqs are disabled
307 * legitimately:
308 */
309#ifdef CONFIG_TRACE_IRQFLAGS
310void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
311{
312 unsigned long flags;
313
314 WARN_ON_ONCE(in_hardirq());
315
316 raw_local_irq_save(flags);
317 /*
318 * The preempt tracer hooks into preempt_count_add and will break
319 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
320 * is set and before current->softirq_enabled is cleared.
321 * We must manually increment preempt_count here and manually
322 * call the trace_preempt_off later.
323 */
324 __preempt_count_add(cnt);
325 /*
326 * Were softirqs turned off above:
327 */
328 if (softirq_count() == (cnt & SOFTIRQ_MASK))
329 lockdep_softirqs_off(ip);
330 raw_local_irq_restore(flags);
331
332 if (preempt_count() == cnt) {
333#ifdef CONFIG_DEBUG_PREEMPT
334 current->preempt_disable_ip = get_lock_parent_ip();
335#endif
336 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
337 }
338}
339EXPORT_SYMBOL(__local_bh_disable_ip);
340#endif /* CONFIG_TRACE_IRQFLAGS */
341
342static void __local_bh_enable(unsigned int cnt)
343{
344 lockdep_assert_irqs_disabled();
345
346 if (preempt_count() == cnt)
347 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
348
349 if (softirq_count() == (cnt & SOFTIRQ_MASK))
350 lockdep_softirqs_on(_RET_IP_);
351
352 __preempt_count_sub(cnt);
353}
354
355/*
356 * Special-case - softirqs can safely be enabled by __do_softirq(),
357 * without processing still-pending softirqs:
358 */
359void _local_bh_enable(void)
360{
361 WARN_ON_ONCE(in_hardirq());
362 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
363}
364EXPORT_SYMBOL(_local_bh_enable);
365
366void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
367{
368 WARN_ON_ONCE(in_hardirq());
369 lockdep_assert_irqs_enabled();
370#ifdef CONFIG_TRACE_IRQFLAGS
371 local_irq_disable();
372#endif
373 /*
374 * Are softirqs going to be turned on now:
375 */
376 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
377 lockdep_softirqs_on(ip);
378 /*
379 * Keep preemption disabled until we are done with
380 * softirq processing:
381 */
382 __preempt_count_sub(cnt - 1);
383
384 if (unlikely(!in_interrupt() && local_softirq_pending())) {
385 /*
386 * Run softirq if any pending. And do it in its own stack
387 * as we may be calling this deep in a task call stack already.
388 */
389 do_softirq();
390 }
391
392 preempt_count_dec();
393#ifdef CONFIG_TRACE_IRQFLAGS
394 local_irq_enable();
395#endif
396 preempt_check_resched();
397}
398EXPORT_SYMBOL(__local_bh_enable_ip);
399
400static inline void softirq_handle_begin(void)
401{
402 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
403}
404
405static inline void softirq_handle_end(void)
406{
407 __local_bh_enable(SOFTIRQ_OFFSET);
408 WARN_ON_ONCE(in_interrupt());
409}
410
411static inline void ksoftirqd_run_begin(void)
412{
413 local_irq_disable();
414}
415
416static inline void ksoftirqd_run_end(void)
417{
418 local_irq_enable();
419}
420
421static inline bool should_wake_ksoftirqd(void)
422{
423 return true;
424}
425
426static inline void invoke_softirq(void)
427{
428 if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
429#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
430 /*
431 * We can safely execute softirq on the current stack if
432 * it is the irq stack, because it should be near empty
433 * at this stage.
434 */
435 __do_softirq();
436#else
437 /*
438 * Otherwise, irq_exit() is called on the task stack that can
439 * be potentially deep already. So call softirq in its own stack
440 * to prevent from any overrun.
441 */
442 do_softirq_own_stack();
443#endif
444 } else {
445 wakeup_softirqd();
446 }
447}
448
449asmlinkage __visible void do_softirq(void)
450{
451 __u32 pending;
452 unsigned long flags;
453
454 if (in_interrupt())
455 return;
456
457 local_irq_save(flags);
458
459 pending = local_softirq_pending();
460
461 if (pending)
462 do_softirq_own_stack();
463
464 local_irq_restore(flags);
465}
466
467#endif /* !CONFIG_PREEMPT_RT */
468
469/*
470 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
471 * but break the loop if need_resched() is set or after 2 ms.
472 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
473 * certain cases, such as stop_machine(), jiffies may cease to
474 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
475 * well to make sure we eventually return from this method.
476 *
477 * These limits have been established via experimentation.
478 * The two things to balance is latency against fairness -
479 * we want to handle softirqs as soon as possible, but they
480 * should not be able to lock up the box.
481 */
482#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
483#define MAX_SOFTIRQ_RESTART 10
484
485#ifdef CONFIG_TRACE_IRQFLAGS
486/*
487 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
488 * to keep the lockdep irq context tracking as tight as possible in order to
489 * not miss-qualify lock contexts and miss possible deadlocks.
490 */
491
492static inline bool lockdep_softirq_start(void)
493{
494 bool in_hardirq = false;
495
496 if (lockdep_hardirq_context()) {
497 in_hardirq = true;
498 lockdep_hardirq_exit();
499 }
500
501 lockdep_softirq_enter();
502
503 return in_hardirq;
504}
505
506static inline void lockdep_softirq_end(bool in_hardirq)
507{
508 lockdep_softirq_exit();
509
510 if (in_hardirq)
511 lockdep_hardirq_enter();
512}
513#else
514static inline bool lockdep_softirq_start(void) { return false; }
515static inline void lockdep_softirq_end(bool in_hardirq) { }
516#endif
517
518static void handle_softirqs(bool ksirqd)
519{
520 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
521 unsigned long old_flags = current->flags;
522 int max_restart = MAX_SOFTIRQ_RESTART;
523 struct softirq_action *h;
524 bool in_hardirq;
525 __u32 pending;
526 int softirq_bit;
527
528 /*
529 * Mask out PF_MEMALLOC as the current task context is borrowed for the
530 * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
531 * again if the socket is related to swapping.
532 */
533 current->flags &= ~PF_MEMALLOC;
534
535 pending = local_softirq_pending();
536
537 softirq_handle_begin();
538 in_hardirq = lockdep_softirq_start();
539 account_softirq_enter(current);
540
541restart:
542 /* Reset the pending bitmask before enabling irqs */
543 set_softirq_pending(0);
544
545 local_irq_enable();
546
547 h = softirq_vec;
548
549 while ((softirq_bit = ffs(pending))) {
550 unsigned int vec_nr;
551 int prev_count;
552
553 h += softirq_bit - 1;
554
555 vec_nr = h - softirq_vec;
556 prev_count = preempt_count();
557
558 kstat_incr_softirqs_this_cpu(vec_nr);
559
560 trace_softirq_entry(vec_nr);
561 h->action();
562 trace_softirq_exit(vec_nr);
563 if (unlikely(prev_count != preempt_count())) {
564 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
565 vec_nr, softirq_to_name[vec_nr], h->action,
566 prev_count, preempt_count());
567 preempt_count_set(prev_count);
568 }
569 h++;
570 pending >>= softirq_bit;
571 }
572
573 if (!IS_ENABLED(CONFIG_PREEMPT_RT) && ksirqd)
574 rcu_softirq_qs();
575
576 local_irq_disable();
577
578 pending = local_softirq_pending();
579 if (pending) {
580 if (time_before(jiffies, end) && !need_resched() &&
581 --max_restart)
582 goto restart;
583
584 wakeup_softirqd();
585 }
586
587 account_softirq_exit(current);
588 lockdep_softirq_end(in_hardirq);
589 softirq_handle_end();
590 current_restore_flags(old_flags, PF_MEMALLOC);
591}
592
593asmlinkage __visible void __softirq_entry __do_softirq(void)
594{
595 handle_softirqs(false);
596}
597
598/**
599 * irq_enter_rcu - Enter an interrupt context with RCU watching
600 */
601void irq_enter_rcu(void)
602{
603 __irq_enter_raw();
604
605 if (tick_nohz_full_cpu(smp_processor_id()) ||
606 (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)))
607 tick_irq_enter();
608
609 account_hardirq_enter(current);
610}
611
612/**
613 * irq_enter - Enter an interrupt context including RCU update
614 */
615void irq_enter(void)
616{
617 ct_irq_enter();
618 irq_enter_rcu();
619}
620
621static inline void tick_irq_exit(void)
622{
623#ifdef CONFIG_NO_HZ_COMMON
624 int cpu = smp_processor_id();
625
626 /* Make sure that timer wheel updates are propagated */
627 if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
628 if (!in_hardirq())
629 tick_nohz_irq_exit();
630 }
631#endif
632}
633
634#ifdef CONFIG_IRQ_FORCED_THREADING
635DEFINE_PER_CPU(struct task_struct *, ktimerd);
636DEFINE_PER_CPU(unsigned long, pending_timer_softirq);
637
638static void wake_timersd(void)
639{
640 struct task_struct *tsk = __this_cpu_read(ktimerd);
641
642 if (tsk)
643 wake_up_process(tsk);
644}
645
646#else
647
648static inline void wake_timersd(void) { }
649
650#endif
651
652static inline void __irq_exit_rcu(void)
653{
654#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
655 local_irq_disable();
656#else
657 lockdep_assert_irqs_disabled();
658#endif
659 account_hardirq_exit(current);
660 preempt_count_sub(HARDIRQ_OFFSET);
661 if (!in_interrupt() && local_softirq_pending())
662 invoke_softirq();
663
664 if (IS_ENABLED(CONFIG_IRQ_FORCED_THREADING) && force_irqthreads() &&
665 local_timers_pending_force_th() && !(in_nmi() | in_hardirq()))
666 wake_timersd();
667
668 tick_irq_exit();
669}
670
671/**
672 * irq_exit_rcu() - Exit an interrupt context without updating RCU
673 *
674 * Also processes softirqs if needed and possible.
675 */
676void irq_exit_rcu(void)
677{
678 __irq_exit_rcu();
679 /* must be last! */
680 lockdep_hardirq_exit();
681}
682
683/**
684 * irq_exit - Exit an interrupt context, update RCU and lockdep
685 *
686 * Also processes softirqs if needed and possible.
687 */
688void irq_exit(void)
689{
690 __irq_exit_rcu();
691 ct_irq_exit();
692 /* must be last! */
693 lockdep_hardirq_exit();
694}
695
696/*
697 * This function must run with irqs disabled!
698 */
699inline void raise_softirq_irqoff(unsigned int nr)
700{
701 __raise_softirq_irqoff(nr);
702
703 /*
704 * If we're in an interrupt or softirq, we're done
705 * (this also catches softirq-disabled code). We will
706 * actually run the softirq once we return from
707 * the irq or softirq.
708 *
709 * Otherwise we wake up ksoftirqd to make sure we
710 * schedule the softirq soon.
711 */
712 if (!in_interrupt() && should_wake_ksoftirqd())
713 wakeup_softirqd();
714}
715
716void raise_softirq(unsigned int nr)
717{
718 unsigned long flags;
719
720 local_irq_save(flags);
721 raise_softirq_irqoff(nr);
722 local_irq_restore(flags);
723}
724
725void __raise_softirq_irqoff(unsigned int nr)
726{
727 lockdep_assert_irqs_disabled();
728 trace_softirq_raise(nr);
729 or_softirq_pending(1UL << nr);
730}
731
732void open_softirq(int nr, void (*action)(void))
733{
734 softirq_vec[nr].action = action;
735}
736
737/*
738 * Tasklets
739 */
740struct tasklet_head {
741 struct tasklet_struct *head;
742 struct tasklet_struct **tail;
743};
744
745static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
746static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
747
748static void __tasklet_schedule_common(struct tasklet_struct *t,
749 struct tasklet_head __percpu *headp,
750 unsigned int softirq_nr)
751{
752 struct tasklet_head *head;
753 unsigned long flags;
754
755 local_irq_save(flags);
756 head = this_cpu_ptr(headp);
757 t->next = NULL;
758 *head->tail = t;
759 head->tail = &(t->next);
760 raise_softirq_irqoff(softirq_nr);
761 local_irq_restore(flags);
762}
763
764void __tasklet_schedule(struct tasklet_struct *t)
765{
766 __tasklet_schedule_common(t, &tasklet_vec,
767 TASKLET_SOFTIRQ);
768}
769EXPORT_SYMBOL(__tasklet_schedule);
770
771void __tasklet_hi_schedule(struct tasklet_struct *t)
772{
773 __tasklet_schedule_common(t, &tasklet_hi_vec,
774 HI_SOFTIRQ);
775}
776EXPORT_SYMBOL(__tasklet_hi_schedule);
777
778static bool tasklet_clear_sched(struct tasklet_struct *t)
779{
780 if (test_and_clear_wake_up_bit(TASKLET_STATE_SCHED, &t->state))
781 return true;
782
783 WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
784 t->use_callback ? "callback" : "func",
785 t->use_callback ? (void *)t->callback : (void *)t->func);
786
787 return false;
788}
789
790static void tasklet_action_common(struct tasklet_head *tl_head,
791 unsigned int softirq_nr)
792{
793 struct tasklet_struct *list;
794
795 local_irq_disable();
796 list = tl_head->head;
797 tl_head->head = NULL;
798 tl_head->tail = &tl_head->head;
799 local_irq_enable();
800
801 while (list) {
802 struct tasklet_struct *t = list;
803
804 list = list->next;
805
806 if (tasklet_trylock(t)) {
807 if (!atomic_read(&t->count)) {
808 if (tasklet_clear_sched(t)) {
809 if (t->use_callback) {
810 trace_tasklet_entry(t, t->callback);
811 t->callback(t);
812 trace_tasklet_exit(t, t->callback);
813 } else {
814 trace_tasklet_entry(t, t->func);
815 t->func(t->data);
816 trace_tasklet_exit(t, t->func);
817 }
818 }
819 tasklet_unlock(t);
820 continue;
821 }
822 tasklet_unlock(t);
823 }
824
825 local_irq_disable();
826 t->next = NULL;
827 *tl_head->tail = t;
828 tl_head->tail = &t->next;
829 __raise_softirq_irqoff(softirq_nr);
830 local_irq_enable();
831 }
832}
833
834static __latent_entropy void tasklet_action(void)
835{
836 workqueue_softirq_action(false);
837 tasklet_action_common(this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
838}
839
840static __latent_entropy void tasklet_hi_action(void)
841{
842 workqueue_softirq_action(true);
843 tasklet_action_common(this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
844}
845
846void tasklet_setup(struct tasklet_struct *t,
847 void (*callback)(struct tasklet_struct *))
848{
849 t->next = NULL;
850 t->state = 0;
851 atomic_set(&t->count, 0);
852 t->callback = callback;
853 t->use_callback = true;
854 t->data = 0;
855}
856EXPORT_SYMBOL(tasklet_setup);
857
858void tasklet_init(struct tasklet_struct *t,
859 void (*func)(unsigned long), unsigned long data)
860{
861 t->next = NULL;
862 t->state = 0;
863 atomic_set(&t->count, 0);
864 t->func = func;
865 t->use_callback = false;
866 t->data = data;
867}
868EXPORT_SYMBOL(tasklet_init);
869
870#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
871/*
872 * Do not use in new code. Waiting for tasklets from atomic contexts is
873 * error prone and should be avoided.
874 */
875void tasklet_unlock_spin_wait(struct tasklet_struct *t)
876{
877 while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
878 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
879 /*
880 * Prevent a live lock when current preempted soft
881 * interrupt processing or prevents ksoftirqd from
882 * running. If the tasklet runs on a different CPU
883 * then this has no effect other than doing the BH
884 * disable/enable dance for nothing.
885 */
886 local_bh_disable();
887 local_bh_enable();
888 } else {
889 cpu_relax();
890 }
891 }
892}
893EXPORT_SYMBOL(tasklet_unlock_spin_wait);
894#endif
895
896void tasklet_kill(struct tasklet_struct *t)
897{
898 if (in_interrupt())
899 pr_notice("Attempt to kill tasklet from interrupt\n");
900
901 wait_on_bit_lock(&t->state, TASKLET_STATE_SCHED, TASK_UNINTERRUPTIBLE);
902
903 tasklet_unlock_wait(t);
904 tasklet_clear_sched(t);
905}
906EXPORT_SYMBOL(tasklet_kill);
907
908#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
909void tasklet_unlock(struct tasklet_struct *t)
910{
911 clear_and_wake_up_bit(TASKLET_STATE_RUN, &t->state);
912}
913EXPORT_SYMBOL_GPL(tasklet_unlock);
914
915void tasklet_unlock_wait(struct tasklet_struct *t)
916{
917 wait_on_bit(&t->state, TASKLET_STATE_RUN, TASK_UNINTERRUPTIBLE);
918}
919EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
920#endif
921
922void __init softirq_init(void)
923{
924 int cpu;
925
926 for_each_possible_cpu(cpu) {
927 per_cpu(tasklet_vec, cpu).tail =
928 &per_cpu(tasklet_vec, cpu).head;
929 per_cpu(tasklet_hi_vec, cpu).tail =
930 &per_cpu(tasklet_hi_vec, cpu).head;
931 }
932
933 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
934 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
935}
936
937static int ksoftirqd_should_run(unsigned int cpu)
938{
939 return local_softirq_pending();
940}
941
942static void run_ksoftirqd(unsigned int cpu)
943{
944 ksoftirqd_run_begin();
945 if (local_softirq_pending()) {
946 /*
947 * We can safely run softirq on inline stack, as we are not deep
948 * in the task stack here.
949 */
950 handle_softirqs(true);
951 ksoftirqd_run_end();
952 cond_resched();
953 return;
954 }
955 ksoftirqd_run_end();
956}
957
958#ifdef CONFIG_HOTPLUG_CPU
959static int takeover_tasklets(unsigned int cpu)
960{
961 workqueue_softirq_dead(cpu);
962
963 /* CPU is dead, so no lock needed. */
964 local_irq_disable();
965
966 /* Find end, append list for that CPU. */
967 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
968 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
969 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
970 per_cpu(tasklet_vec, cpu).head = NULL;
971 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
972 }
973 raise_softirq_irqoff(TASKLET_SOFTIRQ);
974
975 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
976 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
977 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
978 per_cpu(tasklet_hi_vec, cpu).head = NULL;
979 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
980 }
981 raise_softirq_irqoff(HI_SOFTIRQ);
982
983 local_irq_enable();
984 return 0;
985}
986#else
987#define takeover_tasklets NULL
988#endif /* CONFIG_HOTPLUG_CPU */
989
990static struct smp_hotplug_thread softirq_threads = {
991 .store = &ksoftirqd,
992 .thread_should_run = ksoftirqd_should_run,
993 .thread_fn = run_ksoftirqd,
994 .thread_comm = "ksoftirqd/%u",
995};
996
997#ifdef CONFIG_IRQ_FORCED_THREADING
998static void ktimerd_setup(unsigned int cpu)
999{
1000 /* Above SCHED_NORMAL to handle timers before regular tasks. */
1001 sched_set_fifo_low(current);
1002}
1003
1004static int ktimerd_should_run(unsigned int cpu)
1005{
1006 return local_timers_pending_force_th();
1007}
1008
1009void raise_ktimers_thread(unsigned int nr)
1010{
1011 trace_softirq_raise(nr);
1012 __this_cpu_or(pending_timer_softirq, BIT(nr));
1013}
1014
1015static void run_ktimerd(unsigned int cpu)
1016{
1017 unsigned int timer_si;
1018
1019 ksoftirqd_run_begin();
1020
1021 timer_si = local_timers_pending_force_th();
1022 __this_cpu_write(pending_timer_softirq, 0);
1023 or_softirq_pending(timer_si);
1024
1025 __do_softirq();
1026
1027 ksoftirqd_run_end();
1028}
1029
1030static struct smp_hotplug_thread timer_thread = {
1031 .store = &ktimerd,
1032 .setup = ktimerd_setup,
1033 .thread_should_run = ktimerd_should_run,
1034 .thread_fn = run_ktimerd,
1035 .thread_comm = "ktimers/%u",
1036};
1037#endif
1038
1039static __init int spawn_ksoftirqd(void)
1040{
1041 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
1042 takeover_tasklets);
1043 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
1044#ifdef CONFIG_IRQ_FORCED_THREADING
1045 if (force_irqthreads())
1046 BUG_ON(smpboot_register_percpu_thread(&timer_thread));
1047#endif
1048 return 0;
1049}
1050early_initcall(spawn_ksoftirqd);
1051
1052/*
1053 * [ These __weak aliases are kept in a separate compilation unit, so that
1054 * GCC does not inline them incorrectly. ]
1055 */
1056
1057int __init __weak early_irq_init(void)
1058{
1059 return 0;
1060}
1061
1062int __init __weak arch_probe_nr_irqs(void)
1063{
1064 return NR_IRQS_LEGACY;
1065}
1066
1067int __init __weak arch_early_irq_init(void)
1068{
1069 return 0;
1070}
1071
1072unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
1073{
1074 return from;
1075}