Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux...
[platform/adaptation/renesas_rcar/renesas_kernel.git] / kernel / softirq.c
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 #include <linux/export.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/interrupt.h>
14 #include <linux/init.h>
15 #include <linux/mm.h>
16 #include <linux/notifier.h>
17 #include <linux/percpu.h>
18 #include <linux/cpu.h>
19 #include <linux/freezer.h>
20 #include <linux/kthread.h>
21 #include <linux/rcupdate.h>
22 #include <linux/ftrace.h>
23 #include <linux/smp.h>
24 #include <linux/smpboot.h>
25 #include <linux/tick.h>
26
27 #define CREATE_TRACE_POINTS
28 #include <trace/events/irq.h>
29
30 /*
31    - No shared variables, all the data are CPU local.
32    - If a softirq needs serialization, let it serialize itself
33      by its own spinlocks.
34    - Even if softirq is serialized, only local cpu is marked for
35      execution. Hence, we get something sort of weak cpu binding.
36      Though it is still not clear, will it result in better locality
37      or will not.
38
39    Examples:
40    - NET RX softirq. It is multithreaded and does not require
41      any global serialization.
42    - NET TX softirq. It kicks software netdevice queues, hence
43      it is logically serialized per device, but this serialization
44      is invisible to common code.
45    - Tasklets: serialized wrt itself.
46  */
47
48 #ifndef __ARCH_IRQ_STAT
49 irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
50 EXPORT_SYMBOL(irq_stat);
51 #endif
52
53 static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
54
55 DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
56
57 char *softirq_to_name[NR_SOFTIRQS] = {
58         "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
59         "TASKLET", "SCHED", "HRTIMER", "RCU"
60 };
61
62 /*
63  * we cannot loop indefinitely here to avoid userspace starvation,
64  * but we also don't want to introduce a worst case 1/HZ latency
65  * to the pending events, so lets the scheduler to balance
66  * the softirq load for us.
67  */
68 static void wakeup_softirqd(void)
69 {
70         /* Interrupts are disabled: no need to stop preemption */
71         struct task_struct *tsk = __this_cpu_read(ksoftirqd);
72
73         if (tsk && tsk->state != TASK_RUNNING)
74                 wake_up_process(tsk);
75 }
76
77 /*
78  * preempt_count and SOFTIRQ_OFFSET usage:
79  * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
80  *   softirq processing.
81  * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
82  *   on local_bh_disable or local_bh_enable.
83  * This lets us distinguish between whether we are currently processing
84  * softirq and whether we just have bh disabled.
85  */
86
87 /*
88  * This one is for softirq.c-internal use,
89  * where hardirqs are disabled legitimately:
90  */
91 #ifdef CONFIG_TRACE_IRQFLAGS
92 static void __local_bh_disable(unsigned long ip, unsigned int cnt)
93 {
94         unsigned long flags;
95
96         WARN_ON_ONCE(in_irq());
97
98         raw_local_irq_save(flags);
99         /*
100          * The preempt tracer hooks into preempt_count_add and will break
101          * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
102          * is set and before current->softirq_enabled is cleared.
103          * We must manually increment preempt_count here and manually
104          * call the trace_preempt_off later.
105          */
106         __preempt_count_add(cnt);
107         /*
108          * Were softirqs turned off above:
109          */
110         if (softirq_count() == cnt)
111                 trace_softirqs_off(ip);
112         raw_local_irq_restore(flags);
113
114         if (preempt_count() == cnt)
115                 trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
116 }
117 #else /* !CONFIG_TRACE_IRQFLAGS */
118 static inline void __local_bh_disable(unsigned long ip, unsigned int cnt)
119 {
120         preempt_count_add(cnt);
121         barrier();
122 }
123 #endif /* CONFIG_TRACE_IRQFLAGS */
124
125 void local_bh_disable(void)
126 {
127         __local_bh_disable(_RET_IP_, SOFTIRQ_DISABLE_OFFSET);
128 }
129
130 EXPORT_SYMBOL(local_bh_disable);
131
132 static void __local_bh_enable(unsigned int cnt)
133 {
134         WARN_ON_ONCE(!irqs_disabled());
135
136         if (softirq_count() == cnt)
137                 trace_softirqs_on(_RET_IP_);
138         preempt_count_sub(cnt);
139 }
140
141 /*
142  * Special-case - softirqs can safely be enabled in
143  * cond_resched_softirq(), or by __do_softirq(),
144  * without processing still-pending softirqs:
145  */
146 void _local_bh_enable(void)
147 {
148         WARN_ON_ONCE(in_irq());
149         __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
150 }
151
152 EXPORT_SYMBOL(_local_bh_enable);
153
154 static inline void _local_bh_enable_ip(unsigned long ip)
155 {
156         WARN_ON_ONCE(in_irq() || irqs_disabled());
157 #ifdef CONFIG_TRACE_IRQFLAGS
158         local_irq_disable();
159 #endif
160         /*
161          * Are softirqs going to be turned on now:
162          */
163         if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
164                 trace_softirqs_on(ip);
165         /*
166          * Keep preemption disabled until we are done with
167          * softirq processing:
168          */
169         preempt_count_sub(SOFTIRQ_DISABLE_OFFSET - 1);
170
171         if (unlikely(!in_interrupt() && local_softirq_pending())) {
172                 /*
173                  * Run softirq if any pending. And do it in its own stack
174                  * as we may be calling this deep in a task call stack already.
175                  */
176                 do_softirq();
177         }
178
179         preempt_count_dec();
180 #ifdef CONFIG_TRACE_IRQFLAGS
181         local_irq_enable();
182 #endif
183         preempt_check_resched();
184 }
185
186 void local_bh_enable(void)
187 {
188         _local_bh_enable_ip(_RET_IP_);
189 }
190 EXPORT_SYMBOL(local_bh_enable);
191
192 void local_bh_enable_ip(unsigned long ip)
193 {
194         _local_bh_enable_ip(ip);
195 }
196 EXPORT_SYMBOL(local_bh_enable_ip);
197
198 /*
199  * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
200  * but break the loop if need_resched() is set or after 2 ms.
201  * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
202  * certain cases, such as stop_machine(), jiffies may cease to
203  * increment and so we need the MAX_SOFTIRQ_RESTART limit as
204  * well to make sure we eventually return from this method.
205  *
206  * These limits have been established via experimentation.
207  * The two things to balance is latency against fairness -
208  * we want to handle softirqs as soon as possible, but they
209  * should not be able to lock up the box.
210  */
211 #define MAX_SOFTIRQ_TIME  msecs_to_jiffies(2)
212 #define MAX_SOFTIRQ_RESTART 10
213
214 asmlinkage void __do_softirq(void)
215 {
216         struct softirq_action *h;
217         __u32 pending;
218         unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
219         int cpu;
220         unsigned long old_flags = current->flags;
221         int max_restart = MAX_SOFTIRQ_RESTART;
222
223         /*
224          * Mask out PF_MEMALLOC s current task context is borrowed for the
225          * softirq. A softirq handled such as network RX might set PF_MEMALLOC
226          * again if the socket is related to swap
227          */
228         current->flags &= ~PF_MEMALLOC;
229
230         pending = local_softirq_pending();
231         account_irq_enter_time(current);
232
233         __local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET);
234         lockdep_softirq_enter();
235
236         cpu = smp_processor_id();
237 restart:
238         /* Reset the pending bitmask before enabling irqs */
239         set_softirq_pending(0);
240
241         local_irq_enable();
242
243         h = softirq_vec;
244
245         do {
246                 if (pending & 1) {
247                         unsigned int vec_nr = h - softirq_vec;
248                         int prev_count = preempt_count();
249
250                         kstat_incr_softirqs_this_cpu(vec_nr);
251
252                         trace_softirq_entry(vec_nr);
253                         h->action(h);
254                         trace_softirq_exit(vec_nr);
255                         if (unlikely(prev_count != preempt_count())) {
256                                 printk(KERN_ERR "huh, entered softirq %u %s %p"
257                                        "with preempt_count %08x,"
258                                        " exited with %08x?\n", vec_nr,
259                                        softirq_to_name[vec_nr], h->action,
260                                        prev_count, preempt_count());
261                                 preempt_count_set(prev_count);
262                         }
263
264                         rcu_bh_qs(cpu);
265                 }
266                 h++;
267                 pending >>= 1;
268         } while (pending);
269
270         local_irq_disable();
271
272         pending = local_softirq_pending();
273         if (pending) {
274                 if (time_before(jiffies, end) && !need_resched() &&
275                     --max_restart)
276                         goto restart;
277
278                 wakeup_softirqd();
279         }
280
281         lockdep_softirq_exit();
282
283         account_irq_exit_time(current);
284         __local_bh_enable(SOFTIRQ_OFFSET);
285         WARN_ON_ONCE(in_interrupt());
286         tsk_restore_flags(current, old_flags, PF_MEMALLOC);
287 }
288
289
290
291 asmlinkage void do_softirq(void)
292 {
293         __u32 pending;
294         unsigned long flags;
295
296         if (in_interrupt())
297                 return;
298
299         local_irq_save(flags);
300
301         pending = local_softirq_pending();
302
303         if (pending)
304                 do_softirq_own_stack();
305
306         local_irq_restore(flags);
307 }
308
309 /*
310  * Enter an interrupt context.
311  */
312 void irq_enter(void)
313 {
314         int cpu = smp_processor_id();
315
316         rcu_irq_enter();
317         if (is_idle_task(current) && !in_interrupt()) {
318                 /*
319                  * Prevent raise_softirq from needlessly waking up ksoftirqd
320                  * here, as softirq will be serviced on return from interrupt.
321                  */
322                 local_bh_disable();
323                 tick_check_idle(cpu);
324                 _local_bh_enable();
325         }
326
327         __irq_enter();
328 }
329
330 static inline void invoke_softirq(void)
331 {
332         if (!force_irqthreads) {
333 #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
334                 /*
335                  * We can safely execute softirq on the current stack if
336                  * it is the irq stack, because it should be near empty
337                  * at this stage.
338                  */
339                 __do_softirq();
340 #else
341                 /*
342                  * Otherwise, irq_exit() is called on the task stack that can
343                  * be potentially deep already. So call softirq in its own stack
344                  * to prevent from any overrun.
345                  */
346                 do_softirq_own_stack();
347 #endif
348         } else {
349                 wakeup_softirqd();
350         }
351 }
352
353 static inline void tick_irq_exit(void)
354 {
355 #ifdef CONFIG_NO_HZ_COMMON
356         int cpu = smp_processor_id();
357
358         /* Make sure that timer wheel updates are propagated */
359         if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
360                 if (!in_interrupt())
361                         tick_nohz_irq_exit();
362         }
363 #endif
364 }
365
366 /*
367  * Exit an interrupt context. Process softirqs if needed and possible:
368  */
369 void irq_exit(void)
370 {
371 #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
372         local_irq_disable();
373 #else
374         WARN_ON_ONCE(!irqs_disabled());
375 #endif
376
377         account_irq_exit_time(current);
378         trace_hardirq_exit();
379         preempt_count_sub(HARDIRQ_OFFSET);
380         if (!in_interrupt() && local_softirq_pending())
381                 invoke_softirq();
382
383         tick_irq_exit();
384         rcu_irq_exit();
385 }
386
387 /*
388  * This function must run with irqs disabled!
389  */
390 inline void raise_softirq_irqoff(unsigned int nr)
391 {
392         __raise_softirq_irqoff(nr);
393
394         /*
395          * If we're in an interrupt or softirq, we're done
396          * (this also catches softirq-disabled code). We will
397          * actually run the softirq once we return from
398          * the irq or softirq.
399          *
400          * Otherwise we wake up ksoftirqd to make sure we
401          * schedule the softirq soon.
402          */
403         if (!in_interrupt())
404                 wakeup_softirqd();
405 }
406
407 void raise_softirq(unsigned int nr)
408 {
409         unsigned long flags;
410
411         local_irq_save(flags);
412         raise_softirq_irqoff(nr);
413         local_irq_restore(flags);
414 }
415
416 void __raise_softirq_irqoff(unsigned int nr)
417 {
418         trace_softirq_raise(nr);
419         or_softirq_pending(1UL << nr);
420 }
421
422 void open_softirq(int nr, void (*action)(struct softirq_action *))
423 {
424         softirq_vec[nr].action = action;
425 }
426
427 /*
428  * Tasklets
429  */
430 struct tasklet_head
431 {
432         struct tasklet_struct *head;
433         struct tasklet_struct **tail;
434 };
435
436 static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
437 static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
438
439 void __tasklet_schedule(struct tasklet_struct *t)
440 {
441         unsigned long flags;
442
443         local_irq_save(flags);
444         t->next = NULL;
445         *__this_cpu_read(tasklet_vec.tail) = t;
446         __this_cpu_write(tasklet_vec.tail, &(t->next));
447         raise_softirq_irqoff(TASKLET_SOFTIRQ);
448         local_irq_restore(flags);
449 }
450
451 EXPORT_SYMBOL(__tasklet_schedule);
452
453 void __tasklet_hi_schedule(struct tasklet_struct *t)
454 {
455         unsigned long flags;
456
457         local_irq_save(flags);
458         t->next = NULL;
459         *__this_cpu_read(tasklet_hi_vec.tail) = t;
460         __this_cpu_write(tasklet_hi_vec.tail,  &(t->next));
461         raise_softirq_irqoff(HI_SOFTIRQ);
462         local_irq_restore(flags);
463 }
464
465 EXPORT_SYMBOL(__tasklet_hi_schedule);
466
467 void __tasklet_hi_schedule_first(struct tasklet_struct *t)
468 {
469         BUG_ON(!irqs_disabled());
470
471         t->next = __this_cpu_read(tasklet_hi_vec.head);
472         __this_cpu_write(tasklet_hi_vec.head, t);
473         __raise_softirq_irqoff(HI_SOFTIRQ);
474 }
475
476 EXPORT_SYMBOL(__tasklet_hi_schedule_first);
477
478 static void tasklet_action(struct softirq_action *a)
479 {
480         struct tasklet_struct *list;
481
482         local_irq_disable();
483         list = __this_cpu_read(tasklet_vec.head);
484         __this_cpu_write(tasklet_vec.head, NULL);
485         __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head);
486         local_irq_enable();
487
488         while (list) {
489                 struct tasklet_struct *t = list;
490
491                 list = list->next;
492
493                 if (tasklet_trylock(t)) {
494                         if (!atomic_read(&t->count)) {
495                                 if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
496                                         BUG();
497                                 t->func(t->data);
498                                 tasklet_unlock(t);
499                                 continue;
500                         }
501                         tasklet_unlock(t);
502                 }
503
504                 local_irq_disable();
505                 t->next = NULL;
506                 *__this_cpu_read(tasklet_vec.tail) = t;
507                 __this_cpu_write(tasklet_vec.tail, &(t->next));
508                 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
509                 local_irq_enable();
510         }
511 }
512
513 static void tasklet_hi_action(struct softirq_action *a)
514 {
515         struct tasklet_struct *list;
516
517         local_irq_disable();
518         list = __this_cpu_read(tasklet_hi_vec.head);
519         __this_cpu_write(tasklet_hi_vec.head, NULL);
520         __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head);
521         local_irq_enable();
522
523         while (list) {
524                 struct tasklet_struct *t = list;
525
526                 list = list->next;
527
528                 if (tasklet_trylock(t)) {
529                         if (!atomic_read(&t->count)) {
530                                 if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
531                                         BUG();
532                                 t->func(t->data);
533                                 tasklet_unlock(t);
534                                 continue;
535                         }
536                         tasklet_unlock(t);
537                 }
538
539                 local_irq_disable();
540                 t->next = NULL;
541                 *__this_cpu_read(tasklet_hi_vec.tail) = t;
542                 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
543                 __raise_softirq_irqoff(HI_SOFTIRQ);
544                 local_irq_enable();
545         }
546 }
547
548
549 void tasklet_init(struct tasklet_struct *t,
550                   void (*func)(unsigned long), unsigned long data)
551 {
552         t->next = NULL;
553         t->state = 0;
554         atomic_set(&t->count, 0);
555         t->func = func;
556         t->data = data;
557 }
558
559 EXPORT_SYMBOL(tasklet_init);
560
561 void tasklet_kill(struct tasklet_struct *t)
562 {
563         if (in_interrupt())
564                 printk("Attempt to kill tasklet from interrupt\n");
565
566         while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
567                 do {
568                         yield();
569                 } while (test_bit(TASKLET_STATE_SCHED, &t->state));
570         }
571         tasklet_unlock_wait(t);
572         clear_bit(TASKLET_STATE_SCHED, &t->state);
573 }
574
575 EXPORT_SYMBOL(tasklet_kill);
576
577 /*
578  * tasklet_hrtimer
579  */
580
581 /*
582  * The trampoline is called when the hrtimer expires. It schedules a tasklet
583  * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
584  * hrtimer callback, but from softirq context.
585  */
586 static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
587 {
588         struct tasklet_hrtimer *ttimer =
589                 container_of(timer, struct tasklet_hrtimer, timer);
590
591         tasklet_hi_schedule(&ttimer->tasklet);
592         return HRTIMER_NORESTART;
593 }
594
595 /*
596  * Helper function which calls the hrtimer callback from
597  * tasklet/softirq context
598  */
599 static void __tasklet_hrtimer_trampoline(unsigned long data)
600 {
601         struct tasklet_hrtimer *ttimer = (void *)data;
602         enum hrtimer_restart restart;
603
604         restart = ttimer->function(&ttimer->timer);
605         if (restart != HRTIMER_NORESTART)
606                 hrtimer_restart(&ttimer->timer);
607 }
608
609 /**
610  * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
611  * @ttimer:      tasklet_hrtimer which is initialized
612  * @function:    hrtimer callback function which gets called from softirq context
613  * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
614  * @mode:        hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
615  */
616 void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
617                           enum hrtimer_restart (*function)(struct hrtimer *),
618                           clockid_t which_clock, enum hrtimer_mode mode)
619 {
620         hrtimer_init(&ttimer->timer, which_clock, mode);
621         ttimer->timer.function = __hrtimer_tasklet_trampoline;
622         tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
623                      (unsigned long)ttimer);
624         ttimer->function = function;
625 }
626 EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
627
628 void __init softirq_init(void)
629 {
630         int cpu;
631
632         for_each_possible_cpu(cpu) {
633                 per_cpu(tasklet_vec, cpu).tail =
634                         &per_cpu(tasklet_vec, cpu).head;
635                 per_cpu(tasklet_hi_vec, cpu).tail =
636                         &per_cpu(tasklet_hi_vec, cpu).head;
637         }
638
639         open_softirq(TASKLET_SOFTIRQ, tasklet_action);
640         open_softirq(HI_SOFTIRQ, tasklet_hi_action);
641 }
642
643 static int ksoftirqd_should_run(unsigned int cpu)
644 {
645         return local_softirq_pending();
646 }
647
648 static void run_ksoftirqd(unsigned int cpu)
649 {
650         local_irq_disable();
651         if (local_softirq_pending()) {
652                 /*
653                  * We can safely run softirq on inline stack, as we are not deep
654                  * in the task stack here.
655                  */
656                 __do_softirq();
657                 rcu_note_context_switch(cpu);
658                 local_irq_enable();
659                 cond_resched();
660                 return;
661         }
662         local_irq_enable();
663 }
664
665 #ifdef CONFIG_HOTPLUG_CPU
666 /*
667  * tasklet_kill_immediate is called to remove a tasklet which can already be
668  * scheduled for execution on @cpu.
669  *
670  * Unlike tasklet_kill, this function removes the tasklet
671  * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
672  *
673  * When this function is called, @cpu must be in the CPU_DEAD state.
674  */
675 void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
676 {
677         struct tasklet_struct **i;
678
679         BUG_ON(cpu_online(cpu));
680         BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
681
682         if (!test_bit(TASKLET_STATE_SCHED, &t->state))
683                 return;
684
685         /* CPU is dead, so no lock needed. */
686         for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
687                 if (*i == t) {
688                         *i = t->next;
689                         /* If this was the tail element, move the tail ptr */
690                         if (*i == NULL)
691                                 per_cpu(tasklet_vec, cpu).tail = i;
692                         return;
693                 }
694         }
695         BUG();
696 }
697
698 static void takeover_tasklets(unsigned int cpu)
699 {
700         /* CPU is dead, so no lock needed. */
701         local_irq_disable();
702
703         /* Find end, append list for that CPU. */
704         if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
705                 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
706                 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
707                 per_cpu(tasklet_vec, cpu).head = NULL;
708                 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
709         }
710         raise_softirq_irqoff(TASKLET_SOFTIRQ);
711
712         if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
713                 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
714                 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
715                 per_cpu(tasklet_hi_vec, cpu).head = NULL;
716                 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
717         }
718         raise_softirq_irqoff(HI_SOFTIRQ);
719
720         local_irq_enable();
721 }
722 #endif /* CONFIG_HOTPLUG_CPU */
723
724 static int cpu_callback(struct notifier_block *nfb,
725                                   unsigned long action,
726                                   void *hcpu)
727 {
728         switch (action) {
729 #ifdef CONFIG_HOTPLUG_CPU
730         case CPU_DEAD:
731         case CPU_DEAD_FROZEN:
732                 takeover_tasklets((unsigned long)hcpu);
733                 break;
734 #endif /* CONFIG_HOTPLUG_CPU */
735         }
736         return NOTIFY_OK;
737 }
738
739 static struct notifier_block cpu_nfb = {
740         .notifier_call = cpu_callback
741 };
742
743 static struct smp_hotplug_thread softirq_threads = {
744         .store                  = &ksoftirqd,
745         .thread_should_run      = ksoftirqd_should_run,
746         .thread_fn              = run_ksoftirqd,
747         .thread_comm            = "ksoftirqd/%u",
748 };
749
750 static __init int spawn_ksoftirqd(void)
751 {
752         register_cpu_notifier(&cpu_nfb);
753
754         BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
755
756         return 0;
757 }
758 early_initcall(spawn_ksoftirqd);
759
760 /*
761  * [ These __weak aliases are kept in a separate compilation unit, so that
762  *   GCC does not inline them incorrectly. ]
763  */
764
765 int __init __weak early_irq_init(void)
766 {
767         return 0;
768 }
769
770 int __init __weak arch_probe_nr_irqs(void)
771 {
772         return NR_IRQS_LEGACY;
773 }
774
775 int __init __weak arch_early_irq_init(void)
776 {
777         return 0;
778 }