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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 lockdep_assert_irqs_disabled();
141
142 if (softirq_count() == (cnt & SOFTIRQ_MASK))
143 trace_softirqs_on(_RET_IP_);
144 preempt_count_sub(cnt);
145}
146
147/*
148 * Special-case - softirqs can safely be enabled in
149 * cond_resched_softirq(), or by __do_softirq(),
150 * without processing still-pending softirqs:
151 */
152void _local_bh_enable(void)
153{
154 WARN_ON_ONCE(in_irq());
155 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
156}
157EXPORT_SYMBOL(_local_bh_enable);
158
159void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
160{
161 WARN_ON_ONCE(in_irq());
162 lockdep_assert_irqs_enabled();
163#ifdef CONFIG_TRACE_IRQFLAGS
164 local_irq_disable();
165#endif
166 /*
167 * Are softirqs going to be turned on now:
168 */
169 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
170 trace_softirqs_on(ip);
171 /*
172 * Keep preemption disabled until we are done with
173 * softirq processing:
174 */
175 preempt_count_sub(cnt - 1);
176
177 if (unlikely(!in_interrupt() && local_softirq_pending())) {
178 /*
179 * Run softirq if any pending. And do it in its own stack
180 * as we may be calling this deep in a task call stack already.
181 */
182 do_softirq();
183 }
184
185 preempt_count_dec();
186#ifdef CONFIG_TRACE_IRQFLAGS
187 local_irq_enable();
188#endif
189 preempt_check_resched();
190}
191EXPORT_SYMBOL(__local_bh_enable_ip);
192
193/*
194 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
195 * but break the loop if need_resched() is set or after 2 ms.
196 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
197 * certain cases, such as stop_machine(), jiffies may cease to
198 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
199 * well to make sure we eventually return from this method.
200 *
201 * These limits have been established via experimentation.
202 * The two things to balance is latency against fairness -
203 * we want to handle softirqs as soon as possible, but they
204 * should not be able to lock up the box.
205 */
206#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
207#define MAX_SOFTIRQ_RESTART 10
208
209#ifdef CONFIG_TRACE_IRQFLAGS
210/*
211 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
212 * to keep the lockdep irq context tracking as tight as possible in order to
213 * not miss-qualify lock contexts and miss possible deadlocks.
214 */
215
216static inline bool lockdep_softirq_start(void)
217{
218 bool in_hardirq = false;
219
220 if (trace_hardirq_context(current)) {
221 in_hardirq = true;
222 trace_hardirq_exit();
223 }
224
225 lockdep_softirq_enter();
226
227 return in_hardirq;
228}
229
230static inline void lockdep_softirq_end(bool in_hardirq)
231{
232 lockdep_softirq_exit();
233
234 if (in_hardirq)
235 trace_hardirq_enter();
236}
237#else
238static inline bool lockdep_softirq_start(void) { return false; }
239static inline void lockdep_softirq_end(bool in_hardirq) { }
240#endif
241
242asmlinkage __visible void __softirq_entry __do_softirq(void)
243{
244 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
245 unsigned long old_flags = current->flags;
246 int max_restart = MAX_SOFTIRQ_RESTART;
247 struct softirq_action *h;
248 bool in_hardirq;
249 __u32 pending;
250 int softirq_bit;
251
252 /*
253 * Mask out PF_MEMALLOC s current task context is borrowed for the
254 * softirq. A softirq handled such as network RX might set PF_MEMALLOC
255 * again if the socket is related to swap
256 */
257 current->flags &= ~PF_MEMALLOC;
258
259 pending = local_softirq_pending();
260 account_irq_enter_time(current);
261
262 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
263 in_hardirq = lockdep_softirq_start();
264
265restart:
266 /* Reset the pending bitmask before enabling irqs */
267 set_softirq_pending(0);
268
269 local_irq_enable();
270
271 h = softirq_vec;
272
273 while ((softirq_bit = ffs(pending))) {
274 unsigned int vec_nr;
275 int prev_count;
276
277 h += softirq_bit - 1;
278
279 vec_nr = h - softirq_vec;
280 prev_count = preempt_count();
281
282 kstat_incr_softirqs_this_cpu(vec_nr);
283
284 trace_softirq_entry(vec_nr);
285 h->action(h);
286 trace_softirq_exit(vec_nr);
287 if (unlikely(prev_count != preempt_count())) {
288 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
289 vec_nr, softirq_to_name[vec_nr], h->action,
290 prev_count, preempt_count());
291 preempt_count_set(prev_count);
292 }
293 h++;
294 pending >>= softirq_bit;
295 }
296
297 rcu_bh_qs();
298 local_irq_disable();
299
300 pending = local_softirq_pending();
301 if (pending) {
302 if (time_before(jiffies, end) && !need_resched() &&
303 --max_restart)
304 goto restart;
305
306 wakeup_softirqd();
307 }
308
309 lockdep_softirq_end(in_hardirq);
310 account_irq_exit_time(current);
311 __local_bh_enable(SOFTIRQ_OFFSET);
312 WARN_ON_ONCE(in_interrupt());
313 current_restore_flags(old_flags, PF_MEMALLOC);
314}
315
316asmlinkage __visible void do_softirq(void)
317{
318 __u32 pending;
319 unsigned long flags;
320
321 if (in_interrupt())
322 return;
323
324 local_irq_save(flags);
325
326 pending = local_softirq_pending();
327
328 if (pending && !ksoftirqd_running())
329 do_softirq_own_stack();
330
331 local_irq_restore(flags);
332}
333
334/*
335 * Enter an interrupt context.
336 */
337void irq_enter(void)
338{
339 rcu_irq_enter();
340 if (is_idle_task(current) && !in_interrupt()) {
341 /*
342 * Prevent raise_softirq from needlessly waking up ksoftirqd
343 * here, as softirq will be serviced on return from interrupt.
344 */
345 local_bh_disable();
346 tick_irq_enter();
347 _local_bh_enable();
348 }
349
350 __irq_enter();
351}
352
353static inline void invoke_softirq(void)
354{
355 if (ksoftirqd_running())
356 return;
357
358 if (!force_irqthreads) {
359#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
360 /*
361 * We can safely execute softirq on the current stack if
362 * it is the irq stack, because it should be near empty
363 * at this stage.
364 */
365 __do_softirq();
366#else
367 /*
368 * Otherwise, irq_exit() is called on the task stack that can
369 * be potentially deep already. So call softirq in its own stack
370 * to prevent from any overrun.
371 */
372 do_softirq_own_stack();
373#endif
374 } else {
375 wakeup_softirqd();
376 }
377}
378
379static inline void tick_irq_exit(void)
380{
381#ifdef CONFIG_NO_HZ_COMMON
382 int cpu = smp_processor_id();
383
384 /* Make sure that timer wheel updates are propagated */
385 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
386 if (!in_interrupt())
387 tick_nohz_irq_exit();
388 }
389#endif
390}
391
392/*
393 * Exit an interrupt context. Process softirqs if needed and possible:
394 */
395void irq_exit(void)
396{
397#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
398 local_irq_disable();
399#else
400 lockdep_assert_irqs_disabled();
401#endif
402 account_irq_exit_time(current);
403 preempt_count_sub(HARDIRQ_OFFSET);
404 if (!in_interrupt() && local_softirq_pending())
405 invoke_softirq();
406
407 tick_irq_exit();
408 rcu_irq_exit();
409 trace_hardirq_exit(); /* must be last! */
410}
411
412/*
413 * This function must run with irqs disabled!
414 */
415inline void raise_softirq_irqoff(unsigned int nr)
416{
417 __raise_softirq_irqoff(nr);
418
419 /*
420 * If we're in an interrupt or softirq, we're done
421 * (this also catches softirq-disabled code). We will
422 * actually run the softirq once we return from
423 * the irq or softirq.
424 *
425 * Otherwise we wake up ksoftirqd to make sure we
426 * schedule the softirq soon.
427 */
428 if (!in_interrupt())
429 wakeup_softirqd();
430}
431
432void raise_softirq(unsigned int nr)
433{
434 unsigned long flags;
435
436 local_irq_save(flags);
437 raise_softirq_irqoff(nr);
438 local_irq_restore(flags);
439}
440
441void __raise_softirq_irqoff(unsigned int nr)
442{
443 trace_softirq_raise(nr);
444 or_softirq_pending(1UL << nr);
445}
446
447void open_softirq(int nr, void (*action)(struct softirq_action *))
448{
449 softirq_vec[nr].action = action;
450}
451
452/*
453 * Tasklets
454 */
455struct tasklet_head {
456 struct tasklet_struct *head;
457 struct tasklet_struct **tail;
458};
459
460static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
461static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
462
463static void __tasklet_schedule_common(struct tasklet_struct *t,
464 struct tasklet_head __percpu *headp,
465 unsigned int softirq_nr)
466{
467 struct tasklet_head *head;
468 unsigned long flags;
469
470 local_irq_save(flags);
471 head = this_cpu_ptr(headp);
472 t->next = NULL;
473 *head->tail = t;
474 head->tail = &(t->next);
475 raise_softirq_irqoff(softirq_nr);
476 local_irq_restore(flags);
477}
478
479void __tasklet_schedule(struct tasklet_struct *t)
480{
481 __tasklet_schedule_common(t, &tasklet_vec,
482 TASKLET_SOFTIRQ);
483}
484EXPORT_SYMBOL(__tasklet_schedule);
485
486void __tasklet_hi_schedule(struct tasklet_struct *t)
487{
488 __tasklet_schedule_common(t, &tasklet_hi_vec,
489 HI_SOFTIRQ);
490}
491EXPORT_SYMBOL(__tasklet_hi_schedule);
492
493static void tasklet_action_common(struct softirq_action *a,
494 struct tasklet_head *tl_head,
495 unsigned int softirq_nr)
496{
497 struct tasklet_struct *list;
498
499 local_irq_disable();
500 list = tl_head->head;
501 tl_head->head = NULL;
502 tl_head->tail = &tl_head->head;
503 local_irq_enable();
504
505 while (list) {
506 struct tasklet_struct *t = list;
507
508 list = list->next;
509
510 if (tasklet_trylock(t)) {
511 if (!atomic_read(&t->count)) {
512 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
513 &t->state))
514 BUG();
515 t->func(t->data);
516 tasklet_unlock(t);
517 continue;
518 }
519 tasklet_unlock(t);
520 }
521
522 local_irq_disable();
523 t->next = NULL;
524 *tl_head->tail = t;
525 tl_head->tail = &t->next;
526 __raise_softirq_irqoff(softirq_nr);
527 local_irq_enable();
528 }
529}
530
531static __latent_entropy void tasklet_action(struct softirq_action *a)
532{
533 tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
534}
535
536static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
537{
538 tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
539}
540
541void tasklet_init(struct tasklet_struct *t,
542 void (*func)(unsigned long), unsigned long data)
543{
544 t->next = NULL;
545 t->state = 0;
546 atomic_set(&t->count, 0);
547 t->func = func;
548 t->data = data;
549}
550EXPORT_SYMBOL(tasklet_init);
551
552void tasklet_kill(struct tasklet_struct *t)
553{
554 if (in_interrupt())
555 pr_notice("Attempt to kill tasklet from interrupt\n");
556
557 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
558 do {
559 yield();
560 } while (test_bit(TASKLET_STATE_SCHED, &t->state));
561 }
562 tasklet_unlock_wait(t);
563 clear_bit(TASKLET_STATE_SCHED, &t->state);
564}
565EXPORT_SYMBOL(tasklet_kill);
566
567/*
568 * tasklet_hrtimer
569 */
570
571/*
572 * The trampoline is called when the hrtimer expires. It schedules a tasklet
573 * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
574 * hrtimer callback, but from softirq context.
575 */
576static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
577{
578 struct tasklet_hrtimer *ttimer =
579 container_of(timer, struct tasklet_hrtimer, timer);
580
581 tasklet_hi_schedule(&ttimer->tasklet);
582 return HRTIMER_NORESTART;
583}
584
585/*
586 * Helper function which calls the hrtimer callback from
587 * tasklet/softirq context
588 */
589static void __tasklet_hrtimer_trampoline(unsigned long data)
590{
591 struct tasklet_hrtimer *ttimer = (void *)data;
592 enum hrtimer_restart restart;
593
594 restart = ttimer->function(&ttimer->timer);
595 if (restart != HRTIMER_NORESTART)
596 hrtimer_restart(&ttimer->timer);
597}
598
599/**
600 * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
601 * @ttimer: tasklet_hrtimer which is initialized
602 * @function: hrtimer callback function which gets called from softirq context
603 * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
604 * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
605 */
606void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
607 enum hrtimer_restart (*function)(struct hrtimer *),
608 clockid_t which_clock, enum hrtimer_mode mode)
609{
610 hrtimer_init(&ttimer->timer, which_clock, mode);
611 ttimer->timer.function = __hrtimer_tasklet_trampoline;
612 tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
613 (unsigned long)ttimer);
614 ttimer->function = function;
615}
616EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
617
618void __init softirq_init(void)
619{
620 int cpu;
621
622 for_each_possible_cpu(cpu) {
623 per_cpu(tasklet_vec, cpu).tail =
624 &per_cpu(tasklet_vec, cpu).head;
625 per_cpu(tasklet_hi_vec, cpu).tail =
626 &per_cpu(tasklet_hi_vec, cpu).head;
627 }
628
629 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
630 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
631}
632
633static int ksoftirqd_should_run(unsigned int cpu)
634{
635 return local_softirq_pending();
636}
637
638static void run_ksoftirqd(unsigned int cpu)
639{
640 local_irq_disable();
641 if (local_softirq_pending()) {
642 /*
643 * We can safely run softirq on inline stack, as we are not deep
644 * in the task stack here.
645 */
646 __do_softirq();
647 local_irq_enable();
648 cond_resched();
649 return;
650 }
651 local_irq_enable();
652}
653
654#ifdef CONFIG_HOTPLUG_CPU
655/*
656 * tasklet_kill_immediate is called to remove a tasklet which can already be
657 * scheduled for execution on @cpu.
658 *
659 * Unlike tasklet_kill, this function removes the tasklet
660 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
661 *
662 * When this function is called, @cpu must be in the CPU_DEAD state.
663 */
664void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
665{
666 struct tasklet_struct **i;
667
668 BUG_ON(cpu_online(cpu));
669 BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
670
671 if (!test_bit(TASKLET_STATE_SCHED, &t->state))
672 return;
673
674 /* CPU is dead, so no lock needed. */
675 for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
676 if (*i == t) {
677 *i = t->next;
678 /* If this was the tail element, move the tail ptr */
679 if (*i == NULL)
680 per_cpu(tasklet_vec, cpu).tail = i;
681 return;
682 }
683 }
684 BUG();
685}
686
687static int takeover_tasklets(unsigned int cpu)
688{
689 /* CPU is dead, so no lock needed. */
690 local_irq_disable();
691
692 /* Find end, append list for that CPU. */
693 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
694 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
695 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
696 per_cpu(tasklet_vec, cpu).head = NULL;
697 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
698 }
699 raise_softirq_irqoff(TASKLET_SOFTIRQ);
700
701 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
702 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
703 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
704 per_cpu(tasklet_hi_vec, cpu).head = NULL;
705 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
706 }
707 raise_softirq_irqoff(HI_SOFTIRQ);
708
709 local_irq_enable();
710 return 0;
711}
712#else
713#define takeover_tasklets NULL
714#endif /* CONFIG_HOTPLUG_CPU */
715
716static struct smp_hotplug_thread softirq_threads = {
717 .store = &ksoftirqd,
718 .thread_should_run = ksoftirqd_should_run,
719 .thread_fn = run_ksoftirqd,
720 .thread_comm = "ksoftirqd/%u",
721};
722
723static __init int spawn_ksoftirqd(void)
724{
725 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
726 takeover_tasklets);
727 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
728
729 return 0;
730}
731early_initcall(spawn_ksoftirqd);
732
733/*
734 * [ These __weak aliases are kept in a separate compilation unit, so that
735 * GCC does not inline them incorrectly. ]
736 */
737
738int __init __weak early_irq_init(void)
739{
740 return 0;
741}
742
743int __init __weak arch_probe_nr_irqs(void)
744{
745 return NR_IRQS_LEGACY;
746}
747
748int __init __weak arch_early_irq_init(void)
749{
750 return 0;
751}
752
753unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
754{
755 return from;
756}
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 * Remote softirq infrastructure is by Jens Axboe.
11 */
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/tick.h>
27
28#define CREATE_TRACE_POINTS
29#include <trace/events/irq.h>
30
31#include <asm/irq.h>
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
51irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
52EXPORT_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
59char *softirq_to_name[NR_SOFTIRQS] = {
60 "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
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 * preempt_count and SOFTIRQ_OFFSET usage:
81 * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
82 * softirq processing.
83 * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
84 * on local_bh_disable or local_bh_enable.
85 * This lets us distinguish between whether we are currently processing
86 * softirq and whether we just have bh disabled.
87 */
88
89/*
90 * This one is for softirq.c-internal use,
91 * where hardirqs are disabled legitimately:
92 */
93#ifdef CONFIG_TRACE_IRQFLAGS
94static void __local_bh_disable(unsigned long ip, unsigned int cnt)
95{
96 unsigned long flags;
97
98 WARN_ON_ONCE(in_irq());
99
100 raw_local_irq_save(flags);
101 /*
102 * The preempt tracer hooks into add_preempt_count and will break
103 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
104 * is set and before current->softirq_enabled is cleared.
105 * We must manually increment preempt_count here and manually
106 * call the trace_preempt_off later.
107 */
108 preempt_count() += cnt;
109 /*
110 * Were softirqs turned off above:
111 */
112 if (softirq_count() == cnt)
113 trace_softirqs_off(ip);
114 raw_local_irq_restore(flags);
115
116 if (preempt_count() == cnt)
117 trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
118}
119#else /* !CONFIG_TRACE_IRQFLAGS */
120static inline void __local_bh_disable(unsigned long ip, unsigned int cnt)
121{
122 add_preempt_count(cnt);
123 barrier();
124}
125#endif /* CONFIG_TRACE_IRQFLAGS */
126
127void local_bh_disable(void)
128{
129 __local_bh_disable((unsigned long)__builtin_return_address(0),
130 SOFTIRQ_DISABLE_OFFSET);
131}
132
133EXPORT_SYMBOL(local_bh_disable);
134
135static void __local_bh_enable(unsigned int cnt)
136{
137 WARN_ON_ONCE(in_irq());
138 WARN_ON_ONCE(!irqs_disabled());
139
140 if (softirq_count() == cnt)
141 trace_softirqs_on((unsigned long)__builtin_return_address(0));
142 sub_preempt_count(cnt);
143}
144
145/*
146 * Special-case - softirqs can safely be enabled in
147 * cond_resched_softirq(), or by __do_softirq(),
148 * without processing still-pending softirqs:
149 */
150void _local_bh_enable(void)
151{
152 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
153}
154
155EXPORT_SYMBOL(_local_bh_enable);
156
157static inline void _local_bh_enable_ip(unsigned long ip)
158{
159 WARN_ON_ONCE(in_irq() || irqs_disabled());
160#ifdef CONFIG_TRACE_IRQFLAGS
161 local_irq_disable();
162#endif
163 /*
164 * Are softirqs going to be turned on now:
165 */
166 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
167 trace_softirqs_on(ip);
168 /*
169 * Keep preemption disabled until we are done with
170 * softirq processing:
171 */
172 sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1);
173
174 if (unlikely(!in_interrupt() && local_softirq_pending()))
175 do_softirq();
176
177 dec_preempt_count();
178#ifdef CONFIG_TRACE_IRQFLAGS
179 local_irq_enable();
180#endif
181 preempt_check_resched();
182}
183
184void local_bh_enable(void)
185{
186 _local_bh_enable_ip((unsigned long)__builtin_return_address(0));
187}
188EXPORT_SYMBOL(local_bh_enable);
189
190void local_bh_enable_ip(unsigned long ip)
191{
192 _local_bh_enable_ip(ip);
193}
194EXPORT_SYMBOL(local_bh_enable_ip);
195
196/*
197 * We restart softirq processing MAX_SOFTIRQ_RESTART times,
198 * and we fall back to softirqd after that.
199 *
200 * This number has 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_RESTART 10
206
207asmlinkage void __do_softirq(void)
208{
209 struct softirq_action *h;
210 __u32 pending;
211 int max_restart = MAX_SOFTIRQ_RESTART;
212 int cpu;
213
214 pending = local_softirq_pending();
215 account_system_vtime(current);
216
217 __local_bh_disable((unsigned long)__builtin_return_address(0),
218 SOFTIRQ_OFFSET);
219 lockdep_softirq_enter();
220
221 cpu = smp_processor_id();
222restart:
223 /* Reset the pending bitmask before enabling irqs */
224 set_softirq_pending(0);
225
226 local_irq_enable();
227
228 h = softirq_vec;
229
230 do {
231 if (pending & 1) {
232 unsigned int vec_nr = h - softirq_vec;
233 int prev_count = preempt_count();
234
235 kstat_incr_softirqs_this_cpu(vec_nr);
236
237 trace_softirq_entry(vec_nr);
238 h->action(h);
239 trace_softirq_exit(vec_nr);
240 if (unlikely(prev_count != preempt_count())) {
241 printk(KERN_ERR "huh, entered softirq %u %s %p"
242 "with preempt_count %08x,"
243 " exited with %08x?\n", vec_nr,
244 softirq_to_name[vec_nr], h->action,
245 prev_count, preempt_count());
246 preempt_count() = prev_count;
247 }
248
249 rcu_bh_qs(cpu);
250 }
251 h++;
252 pending >>= 1;
253 } while (pending);
254
255 local_irq_disable();
256
257 pending = local_softirq_pending();
258 if (pending && --max_restart)
259 goto restart;
260
261 if (pending)
262 wakeup_softirqd();
263
264 lockdep_softirq_exit();
265
266 account_system_vtime(current);
267 __local_bh_enable(SOFTIRQ_OFFSET);
268}
269
270#ifndef __ARCH_HAS_DO_SOFTIRQ
271
272asmlinkage void do_softirq(void)
273{
274 __u32 pending;
275 unsigned long flags;
276
277 if (in_interrupt())
278 return;
279
280 local_irq_save(flags);
281
282 pending = local_softirq_pending();
283
284 if (pending)
285 __do_softirq();
286
287 local_irq_restore(flags);
288}
289
290#endif
291
292/*
293 * Enter an interrupt context.
294 */
295void irq_enter(void)
296{
297 int cpu = smp_processor_id();
298
299 rcu_irq_enter();
300 if (is_idle_task(current) && !in_interrupt()) {
301 /*
302 * Prevent raise_softirq from needlessly waking up ksoftirqd
303 * here, as softirq will be serviced on return from interrupt.
304 */
305 local_bh_disable();
306 tick_check_idle(cpu);
307 _local_bh_enable();
308 }
309
310 __irq_enter();
311}
312
313static inline void invoke_softirq(void)
314{
315 if (!force_irqthreads) {
316#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
317 __do_softirq();
318#else
319 do_softirq();
320#endif
321 } else {
322 __local_bh_disable((unsigned long)__builtin_return_address(0),
323 SOFTIRQ_OFFSET);
324 wakeup_softirqd();
325 __local_bh_enable(SOFTIRQ_OFFSET);
326 }
327}
328
329/*
330 * Exit an interrupt context. Process softirqs if needed and possible:
331 */
332void irq_exit(void)
333{
334 account_system_vtime(current);
335 trace_hardirq_exit();
336 sub_preempt_count(IRQ_EXIT_OFFSET);
337 if (!in_interrupt() && local_softirq_pending())
338 invoke_softirq();
339
340#ifdef CONFIG_NO_HZ
341 /* Make sure that timer wheel updates are propagated */
342 if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
343 tick_nohz_irq_exit();
344#endif
345 rcu_irq_exit();
346 sched_preempt_enable_no_resched();
347}
348
349/*
350 * This function must run with irqs disabled!
351 */
352inline void raise_softirq_irqoff(unsigned int nr)
353{
354 __raise_softirq_irqoff(nr);
355
356 /*
357 * If we're in an interrupt or softirq, we're done
358 * (this also catches softirq-disabled code). We will
359 * actually run the softirq once we return from
360 * the irq or softirq.
361 *
362 * Otherwise we wake up ksoftirqd to make sure we
363 * schedule the softirq soon.
364 */
365 if (!in_interrupt())
366 wakeup_softirqd();
367}
368
369void raise_softirq(unsigned int nr)
370{
371 unsigned long flags;
372
373 local_irq_save(flags);
374 raise_softirq_irqoff(nr);
375 local_irq_restore(flags);
376}
377
378void __raise_softirq_irqoff(unsigned int nr)
379{
380 trace_softirq_raise(nr);
381 or_softirq_pending(1UL << nr);
382}
383
384void open_softirq(int nr, void (*action)(struct softirq_action *))
385{
386 softirq_vec[nr].action = action;
387}
388
389/*
390 * Tasklets
391 */
392struct tasklet_head
393{
394 struct tasklet_struct *head;
395 struct tasklet_struct **tail;
396};
397
398static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
399static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
400
401void __tasklet_schedule(struct tasklet_struct *t)
402{
403 unsigned long flags;
404
405 local_irq_save(flags);
406 t->next = NULL;
407 *__this_cpu_read(tasklet_vec.tail) = t;
408 __this_cpu_write(tasklet_vec.tail, &(t->next));
409 raise_softirq_irqoff(TASKLET_SOFTIRQ);
410 local_irq_restore(flags);
411}
412
413EXPORT_SYMBOL(__tasklet_schedule);
414
415void __tasklet_hi_schedule(struct tasklet_struct *t)
416{
417 unsigned long flags;
418
419 local_irq_save(flags);
420 t->next = NULL;
421 *__this_cpu_read(tasklet_hi_vec.tail) = t;
422 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
423 raise_softirq_irqoff(HI_SOFTIRQ);
424 local_irq_restore(flags);
425}
426
427EXPORT_SYMBOL(__tasklet_hi_schedule);
428
429void __tasklet_hi_schedule_first(struct tasklet_struct *t)
430{
431 BUG_ON(!irqs_disabled());
432
433 t->next = __this_cpu_read(tasklet_hi_vec.head);
434 __this_cpu_write(tasklet_hi_vec.head, t);
435 __raise_softirq_irqoff(HI_SOFTIRQ);
436}
437
438EXPORT_SYMBOL(__tasklet_hi_schedule_first);
439
440static void tasklet_action(struct softirq_action *a)
441{
442 struct tasklet_struct *list;
443
444 local_irq_disable();
445 list = __this_cpu_read(tasklet_vec.head);
446 __this_cpu_write(tasklet_vec.head, NULL);
447 __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head);
448 local_irq_enable();
449
450 while (list) {
451 struct tasklet_struct *t = list;
452
453 list = list->next;
454
455 if (tasklet_trylock(t)) {
456 if (!atomic_read(&t->count)) {
457 if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
458 BUG();
459 t->func(t->data);
460 tasklet_unlock(t);
461 continue;
462 }
463 tasklet_unlock(t);
464 }
465
466 local_irq_disable();
467 t->next = NULL;
468 *__this_cpu_read(tasklet_vec.tail) = t;
469 __this_cpu_write(tasklet_vec.tail, &(t->next));
470 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
471 local_irq_enable();
472 }
473}
474
475static void tasklet_hi_action(struct softirq_action *a)
476{
477 struct tasklet_struct *list;
478
479 local_irq_disable();
480 list = __this_cpu_read(tasklet_hi_vec.head);
481 __this_cpu_write(tasklet_hi_vec.head, NULL);
482 __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head);
483 local_irq_enable();
484
485 while (list) {
486 struct tasklet_struct *t = list;
487
488 list = list->next;
489
490 if (tasklet_trylock(t)) {
491 if (!atomic_read(&t->count)) {
492 if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
493 BUG();
494 t->func(t->data);
495 tasklet_unlock(t);
496 continue;
497 }
498 tasklet_unlock(t);
499 }
500
501 local_irq_disable();
502 t->next = NULL;
503 *__this_cpu_read(tasklet_hi_vec.tail) = t;
504 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
505 __raise_softirq_irqoff(HI_SOFTIRQ);
506 local_irq_enable();
507 }
508}
509
510
511void tasklet_init(struct tasklet_struct *t,
512 void (*func)(unsigned long), unsigned long data)
513{
514 t->next = NULL;
515 t->state = 0;
516 atomic_set(&t->count, 0);
517 t->func = func;
518 t->data = data;
519}
520
521EXPORT_SYMBOL(tasklet_init);
522
523void tasklet_kill(struct tasklet_struct *t)
524{
525 if (in_interrupt())
526 printk("Attempt to kill tasklet from interrupt\n");
527
528 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
529 do {
530 yield();
531 } while (test_bit(TASKLET_STATE_SCHED, &t->state));
532 }
533 tasklet_unlock_wait(t);
534 clear_bit(TASKLET_STATE_SCHED, &t->state);
535}
536
537EXPORT_SYMBOL(tasklet_kill);
538
539/*
540 * tasklet_hrtimer
541 */
542
543/*
544 * The trampoline is called when the hrtimer expires. It schedules a tasklet
545 * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
546 * hrtimer callback, but from softirq context.
547 */
548static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
549{
550 struct tasklet_hrtimer *ttimer =
551 container_of(timer, struct tasklet_hrtimer, timer);
552
553 tasklet_hi_schedule(&ttimer->tasklet);
554 return HRTIMER_NORESTART;
555}
556
557/*
558 * Helper function which calls the hrtimer callback from
559 * tasklet/softirq context
560 */
561static void __tasklet_hrtimer_trampoline(unsigned long data)
562{
563 struct tasklet_hrtimer *ttimer = (void *)data;
564 enum hrtimer_restart restart;
565
566 restart = ttimer->function(&ttimer->timer);
567 if (restart != HRTIMER_NORESTART)
568 hrtimer_restart(&ttimer->timer);
569}
570
571/**
572 * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
573 * @ttimer: tasklet_hrtimer which is initialized
574 * @function: hrtimer callback function which gets called from softirq context
575 * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
576 * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
577 */
578void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
579 enum hrtimer_restart (*function)(struct hrtimer *),
580 clockid_t which_clock, enum hrtimer_mode mode)
581{
582 hrtimer_init(&ttimer->timer, which_clock, mode);
583 ttimer->timer.function = __hrtimer_tasklet_trampoline;
584 tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
585 (unsigned long)ttimer);
586 ttimer->function = function;
587}
588EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
589
590/*
591 * Remote softirq bits
592 */
593
594DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list);
595EXPORT_PER_CPU_SYMBOL(softirq_work_list);
596
597static void __local_trigger(struct call_single_data *cp, int softirq)
598{
599 struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]);
600
601 list_add_tail(&cp->list, head);
602
603 /* Trigger the softirq only if the list was previously empty. */
604 if (head->next == &cp->list)
605 raise_softirq_irqoff(softirq);
606}
607
608#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
609static void remote_softirq_receive(void *data)
610{
611 struct call_single_data *cp = data;
612 unsigned long flags;
613 int softirq;
614
615 softirq = cp->priv;
616
617 local_irq_save(flags);
618 __local_trigger(cp, softirq);
619 local_irq_restore(flags);
620}
621
622static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
623{
624 if (cpu_online(cpu)) {
625 cp->func = remote_softirq_receive;
626 cp->info = cp;
627 cp->flags = 0;
628 cp->priv = softirq;
629
630 __smp_call_function_single(cpu, cp, 0);
631 return 0;
632 }
633 return 1;
634}
635#else /* CONFIG_USE_GENERIC_SMP_HELPERS */
636static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
637{
638 return 1;
639}
640#endif
641
642/**
643 * __send_remote_softirq - try to schedule softirq work on a remote cpu
644 * @cp: private SMP call function data area
645 * @cpu: the remote cpu
646 * @this_cpu: the currently executing cpu
647 * @softirq: the softirq for the work
648 *
649 * Attempt to schedule softirq work on a remote cpu. If this cannot be
650 * done, the work is instead queued up on the local cpu.
651 *
652 * Interrupts must be disabled.
653 */
654void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq)
655{
656 if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq))
657 __local_trigger(cp, softirq);
658}
659EXPORT_SYMBOL(__send_remote_softirq);
660
661/**
662 * send_remote_softirq - try to schedule softirq work on a remote cpu
663 * @cp: private SMP call function data area
664 * @cpu: the remote cpu
665 * @softirq: the softirq for the work
666 *
667 * Like __send_remote_softirq except that disabling interrupts and
668 * computing the current cpu is done for the caller.
669 */
670void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
671{
672 unsigned long flags;
673 int this_cpu;
674
675 local_irq_save(flags);
676 this_cpu = smp_processor_id();
677 __send_remote_softirq(cp, cpu, this_cpu, softirq);
678 local_irq_restore(flags);
679}
680EXPORT_SYMBOL(send_remote_softirq);
681
682static int __cpuinit remote_softirq_cpu_notify(struct notifier_block *self,
683 unsigned long action, void *hcpu)
684{
685 /*
686 * If a CPU goes away, splice its entries to the current CPU
687 * and trigger a run of the softirq
688 */
689 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
690 int cpu = (unsigned long) hcpu;
691 int i;
692
693 local_irq_disable();
694 for (i = 0; i < NR_SOFTIRQS; i++) {
695 struct list_head *head = &per_cpu(softirq_work_list[i], cpu);
696 struct list_head *local_head;
697
698 if (list_empty(head))
699 continue;
700
701 local_head = &__get_cpu_var(softirq_work_list[i]);
702 list_splice_init(head, local_head);
703 raise_softirq_irqoff(i);
704 }
705 local_irq_enable();
706 }
707
708 return NOTIFY_OK;
709}
710
711static struct notifier_block __cpuinitdata remote_softirq_cpu_notifier = {
712 .notifier_call = remote_softirq_cpu_notify,
713};
714
715void __init softirq_init(void)
716{
717 int cpu;
718
719 for_each_possible_cpu(cpu) {
720 int i;
721
722 per_cpu(tasklet_vec, cpu).tail =
723 &per_cpu(tasklet_vec, cpu).head;
724 per_cpu(tasklet_hi_vec, cpu).tail =
725 &per_cpu(tasklet_hi_vec, cpu).head;
726 for (i = 0; i < NR_SOFTIRQS; i++)
727 INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu));
728 }
729
730 register_hotcpu_notifier(&remote_softirq_cpu_notifier);
731
732 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
733 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
734}
735
736static int run_ksoftirqd(void * __bind_cpu)
737{
738 set_current_state(TASK_INTERRUPTIBLE);
739
740 while (!kthread_should_stop()) {
741 preempt_disable();
742 if (!local_softirq_pending()) {
743 schedule_preempt_disabled();
744 }
745
746 __set_current_state(TASK_RUNNING);
747
748 while (local_softirq_pending()) {
749 /* Preempt disable stops cpu going offline.
750 If already offline, we'll be on wrong CPU:
751 don't process */
752 if (cpu_is_offline((long)__bind_cpu))
753 goto wait_to_die;
754 local_irq_disable();
755 if (local_softirq_pending())
756 __do_softirq();
757 local_irq_enable();
758 sched_preempt_enable_no_resched();
759 cond_resched();
760 preempt_disable();
761 rcu_note_context_switch((long)__bind_cpu);
762 }
763 preempt_enable();
764 set_current_state(TASK_INTERRUPTIBLE);
765 }
766 __set_current_state(TASK_RUNNING);
767 return 0;
768
769wait_to_die:
770 preempt_enable();
771 /* Wait for kthread_stop */
772 set_current_state(TASK_INTERRUPTIBLE);
773 while (!kthread_should_stop()) {
774 schedule();
775 set_current_state(TASK_INTERRUPTIBLE);
776 }
777 __set_current_state(TASK_RUNNING);
778 return 0;
779}
780
781#ifdef CONFIG_HOTPLUG_CPU
782/*
783 * tasklet_kill_immediate is called to remove a tasklet which can already be
784 * scheduled for execution on @cpu.
785 *
786 * Unlike tasklet_kill, this function removes the tasklet
787 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
788 *
789 * When this function is called, @cpu must be in the CPU_DEAD state.
790 */
791void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
792{
793 struct tasklet_struct **i;
794
795 BUG_ON(cpu_online(cpu));
796 BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
797
798 if (!test_bit(TASKLET_STATE_SCHED, &t->state))
799 return;
800
801 /* CPU is dead, so no lock needed. */
802 for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
803 if (*i == t) {
804 *i = t->next;
805 /* If this was the tail element, move the tail ptr */
806 if (*i == NULL)
807 per_cpu(tasklet_vec, cpu).tail = i;
808 return;
809 }
810 }
811 BUG();
812}
813
814static void takeover_tasklets(unsigned int cpu)
815{
816 /* CPU is dead, so no lock needed. */
817 local_irq_disable();
818
819 /* Find end, append list for that CPU. */
820 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
821 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
822 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
823 per_cpu(tasklet_vec, cpu).head = NULL;
824 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
825 }
826 raise_softirq_irqoff(TASKLET_SOFTIRQ);
827
828 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
829 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
830 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
831 per_cpu(tasklet_hi_vec, cpu).head = NULL;
832 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
833 }
834 raise_softirq_irqoff(HI_SOFTIRQ);
835
836 local_irq_enable();
837}
838#endif /* CONFIG_HOTPLUG_CPU */
839
840static int __cpuinit cpu_callback(struct notifier_block *nfb,
841 unsigned long action,
842 void *hcpu)
843{
844 int hotcpu = (unsigned long)hcpu;
845 struct task_struct *p;
846
847 switch (action) {
848 case CPU_UP_PREPARE:
849 case CPU_UP_PREPARE_FROZEN:
850 p = kthread_create_on_node(run_ksoftirqd,
851 hcpu,
852 cpu_to_node(hotcpu),
853 "ksoftirqd/%d", hotcpu);
854 if (IS_ERR(p)) {
855 printk("ksoftirqd for %i failed\n", hotcpu);
856 return notifier_from_errno(PTR_ERR(p));
857 }
858 kthread_bind(p, hotcpu);
859 per_cpu(ksoftirqd, hotcpu) = p;
860 break;
861 case CPU_ONLINE:
862 case CPU_ONLINE_FROZEN:
863 wake_up_process(per_cpu(ksoftirqd, hotcpu));
864 break;
865#ifdef CONFIG_HOTPLUG_CPU
866 case CPU_UP_CANCELED:
867 case CPU_UP_CANCELED_FROZEN:
868 if (!per_cpu(ksoftirqd, hotcpu))
869 break;
870 /* Unbind so it can run. Fall thru. */
871 kthread_bind(per_cpu(ksoftirqd, hotcpu),
872 cpumask_any(cpu_online_mask));
873 case CPU_DEAD:
874 case CPU_DEAD_FROZEN: {
875 static const struct sched_param param = {
876 .sched_priority = MAX_RT_PRIO-1
877 };
878
879 p = per_cpu(ksoftirqd, hotcpu);
880 per_cpu(ksoftirqd, hotcpu) = NULL;
881 sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m);
882 kthread_stop(p);
883 takeover_tasklets(hotcpu);
884 break;
885 }
886#endif /* CONFIG_HOTPLUG_CPU */
887 }
888 return NOTIFY_OK;
889}
890
891static struct notifier_block __cpuinitdata cpu_nfb = {
892 .notifier_call = cpu_callback
893};
894
895static __init int spawn_ksoftirqd(void)
896{
897 void *cpu = (void *)(long)smp_processor_id();
898 int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
899
900 BUG_ON(err != NOTIFY_OK);
901 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
902 register_cpu_notifier(&cpu_nfb);
903 return 0;
904}
905early_initcall(spawn_ksoftirqd);
906
907/*
908 * [ These __weak aliases are kept in a separate compilation unit, so that
909 * GCC does not inline them incorrectly. ]
910 */
911
912int __init __weak early_irq_init(void)
913{
914 return 0;
915}
916
917#ifdef CONFIG_GENERIC_HARDIRQS
918int __init __weak arch_probe_nr_irqs(void)
919{
920 return NR_IRQS_LEGACY;
921}
922
923int __init __weak arch_early_irq_init(void)
924{
925 return 0;
926}
927#endif