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path: root/kernel/softirq.c (plain)
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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 * unless we're doing some of the synchronous softirqs.
84 */
85#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ))
86static bool ksoftirqd_running(unsigned long pending)
87{
88 struct task_struct *tsk = __this_cpu_read(ksoftirqd);
89
90 if (pending & SOFTIRQ_NOW_MASK)
91 return false;
92 return tsk && (tsk->state == TASK_RUNNING);
93}
94
95/*
96 * preempt_count and SOFTIRQ_OFFSET usage:
97 * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
98 * softirq processing.
99 * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
100 * on local_bh_disable or local_bh_enable.
101 * This lets us distinguish between whether we are currently processing
102 * softirq and whether we just have bh disabled.
103 */
104
105/*
106 * This one is for softirq.c-internal use,
107 * where hardirqs are disabled legitimately:
108 */
109#ifdef CONFIG_TRACE_IRQFLAGS
110void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
111{
112 unsigned long flags;
113
114 WARN_ON_ONCE(in_irq());
115
116 raw_local_irq_save(flags);
117 /*
118 * The preempt tracer hooks into preempt_count_add and will break
119 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
120 * is set and before current->softirq_enabled is cleared.
121 * We must manually increment preempt_count here and manually
122 * call the trace_preempt_off later.
123 */
124 __preempt_count_add(cnt);
125 /*
126 * Were softirqs turned off above:
127 */
128 if (softirq_count() == (cnt & SOFTIRQ_MASK))
129 trace_softirqs_off(ip);
130 raw_local_irq_restore(flags);
131
132 if (preempt_count() == cnt) {
133#ifdef CONFIG_DEBUG_PREEMPT
134 current->preempt_disable_ip = get_lock_parent_ip();
135#endif
136 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
137 }
138}
139EXPORT_SYMBOL(__local_bh_disable_ip);
140#endif /* CONFIG_TRACE_IRQFLAGS */
141
142static void __local_bh_enable(unsigned int cnt)
143{
144 WARN_ON_ONCE(!irqs_disabled());
145
146 if (softirq_count() == (cnt & SOFTIRQ_MASK))
147 trace_softirqs_on(_RET_IP_);
148 preempt_count_sub(cnt);
149}
150
151/*
152 * Special-case - softirqs can safely be enabled in
153 * cond_resched_softirq(), or by __do_softirq(),
154 * without processing still-pending softirqs:
155 */
156void _local_bh_enable(void)
157{
158 WARN_ON_ONCE(in_irq());
159 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
160}
161EXPORT_SYMBOL(_local_bh_enable);
162
163void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
164{
165 WARN_ON_ONCE(in_irq() || irqs_disabled());
166#ifdef CONFIG_TRACE_IRQFLAGS
167 local_irq_disable();
168#endif
169 /*
170 * Are softirqs going to be turned on now:
171 */
172 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
173 trace_softirqs_on(ip);
174 /*
175 * Keep preemption disabled until we are done with
176 * softirq processing:
177 */
178 preempt_count_sub(cnt - 1);
179
180 if (unlikely(!in_interrupt() && local_softirq_pending())) {
181 /*
182 * Run softirq if any pending. And do it in its own stack
183 * as we may be calling this deep in a task call stack already.
184 */
185 do_softirq();
186 }
187
188 preempt_count_dec();
189#ifdef CONFIG_TRACE_IRQFLAGS
190 local_irq_enable();
191#endif
192 preempt_check_resched();
193}
194EXPORT_SYMBOL(__local_bh_enable_ip);
195
196/*
197 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
198 * but break the loop if need_resched() is set or after 2 ms.
199 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
200 * certain cases, such as stop_machine(), jiffies may cease to
201 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
202 * well to make sure we eventually return from this method.
203 *
204 * These limits have been established via experimentation.
205 * The two things to balance is latency against fairness -
206 * we want to handle softirqs as soon as possible, but they
207 * should not be able to lock up the box.
208 */
209#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
210#define MAX_SOFTIRQ_RESTART 10
211
212#ifdef CONFIG_TRACE_IRQFLAGS
213/*
214 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
215 * to keep the lockdep irq context tracking as tight as possible in order to
216 * not miss-qualify lock contexts and miss possible deadlocks.
217 */
218
219static inline bool lockdep_softirq_start(void)
220{
221 bool in_hardirq = false;
222
223 if (trace_hardirq_context(current)) {
224 in_hardirq = true;
225 trace_hardirq_exit();
226 }
227
228 lockdep_softirq_enter();
229
230 return in_hardirq;
231}
232
233static inline void lockdep_softirq_end(bool in_hardirq)
234{
235 lockdep_softirq_exit();
236
237 if (in_hardirq)
238 trace_hardirq_enter();
239}
240#else
241static inline bool lockdep_softirq_start(void) { return false; }
242static inline void lockdep_softirq_end(bool in_hardirq) { }
243#endif
244
245asmlinkage __visible void __softirq_entry __do_softirq(void)
246{
247 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
248 unsigned long old_flags = current->flags;
249 int max_restart = MAX_SOFTIRQ_RESTART;
250 struct softirq_action *h;
251 bool in_hardirq;
252 __u32 pending;
253 int softirq_bit;
254#ifdef CONFIG_AMLOGIC_DEBUG_LOCKUP
255 int cpu;
256 unsigned long long tin;
257#endif
258
259 /*
260 * Mask out PF_MEMALLOC s current task context is borrowed for the
261 * softirq. A softirq handled such as network RX might set PF_MEMALLOC
262 * again if the socket is related to swap
263 */
264 current->flags &= ~PF_MEMALLOC;
265
266 pending = local_softirq_pending();
267 account_irq_enter_time(current);
268
269 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
270 in_hardirq = lockdep_softirq_start();
271
272restart:
273 /* Reset the pending bitmask before enabling irqs */
274 set_softirq_pending(0);
275
276 local_irq_enable();
277
278 h = softirq_vec;
279
280 while ((softirq_bit = ffs(pending))) {
281 unsigned int vec_nr;
282 int prev_count;
283
284 h += softirq_bit - 1;
285
286 vec_nr = h - softirq_vec;
287 prev_count = preempt_count();
288
289 kstat_incr_softirqs_this_cpu(vec_nr);
290
291 trace_softirq_entry(vec_nr);
292#ifdef CONFIG_AMLOGIC_DEBUG_LOCKUP
293 cpu = smp_processor_id();
294 sirq_in_hook(cpu, &tin, (void *)h->action);
295#endif
296 h->action(h);
297#ifdef CONFIG_AMLOGIC_DEBUG_LOCKUP
298 sirq_out_hook(cpu, tin, (void *)h->action);
299#endif
300 trace_softirq_exit(vec_nr);
301 if (unlikely(prev_count != preempt_count())) {
302 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
303 vec_nr, softirq_to_name[vec_nr], h->action,
304 prev_count, preempt_count());
305 preempt_count_set(prev_count);
306 }
307 h++;
308 pending >>= softirq_bit;
309 }
310
311 rcu_bh_qs();
312 local_irq_disable();
313
314 pending = local_softirq_pending();
315 if (pending) {
316 if (time_before(jiffies, end) && !need_resched() &&
317 --max_restart)
318 goto restart;
319
320 wakeup_softirqd();
321 }
322
323 lockdep_softirq_end(in_hardirq);
324 account_irq_exit_time(current);
325 __local_bh_enable(SOFTIRQ_OFFSET);
326 WARN_ON_ONCE(in_interrupt());
327 tsk_restore_flags(current, old_flags, PF_MEMALLOC);
328}
329
330asmlinkage __visible void do_softirq(void)
331{
332 __u32 pending;
333 unsigned long flags;
334
335 if (in_interrupt())
336 return;
337
338 local_irq_save(flags);
339
340 pending = local_softirq_pending();
341
342 if (pending && !ksoftirqd_running(pending))
343 do_softirq_own_stack();
344
345 local_irq_restore(flags);
346}
347
348/*
349 * Enter an interrupt context.
350 */
351void irq_enter(void)
352{
353 rcu_irq_enter();
354 if (is_idle_task(current) && !in_interrupt()) {
355 /*
356 * Prevent raise_softirq from needlessly waking up ksoftirqd
357 * here, as softirq will be serviced on return from interrupt.
358 */
359 local_bh_disable();
360 tick_irq_enter();
361 _local_bh_enable();
362 }
363
364 __irq_enter();
365}
366
367static inline void invoke_softirq(void)
368{
369 if (ksoftirqd_running(local_softirq_pending()))
370 return;
371
372 if (!force_irqthreads) {
373#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
374 /*
375 * We can safely execute softirq on the current stack if
376 * it is the irq stack, because it should be near empty
377 * at this stage.
378 */
379 __do_softirq();
380#else
381 /*
382 * Otherwise, irq_exit() is called on the task stack that can
383 * be potentially deep already. So call softirq in its own stack
384 * to prevent from any overrun.
385 */
386 do_softirq_own_stack();
387#endif
388 } else {
389 wakeup_softirqd();
390 }
391}
392
393static inline void tick_irq_exit(void)
394{
395#ifdef CONFIG_NO_HZ_COMMON
396 int cpu = smp_processor_id();
397
398 /* Make sure that timer wheel updates are propagated */
399 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
400 if (!in_interrupt())
401 tick_nohz_irq_exit();
402 }
403#endif
404}
405
406/*
407 * Exit an interrupt context. Process softirqs if needed and possible:
408 */
409void irq_exit(void)
410{
411#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
412 local_irq_disable();
413#else
414 WARN_ON_ONCE(!irqs_disabled());
415#endif
416
417 account_irq_exit_time(current);
418 preempt_count_sub(HARDIRQ_OFFSET);
419 if (!in_interrupt() && local_softirq_pending())
420 invoke_softirq();
421
422 tick_irq_exit();
423 rcu_irq_exit();
424 trace_hardirq_exit(); /* must be last! */
425}
426
427/*
428 * This function must run with irqs disabled!
429 */
430inline void raise_softirq_irqoff(unsigned int nr)
431{
432 __raise_softirq_irqoff(nr);
433
434 /*
435 * If we're in an interrupt or softirq, we're done
436 * (this also catches softirq-disabled code). We will
437 * actually run the softirq once we return from
438 * the irq or softirq.
439 *
440 * Otherwise we wake up ksoftirqd to make sure we
441 * schedule the softirq soon.
442 */
443 if (!in_interrupt())
444 wakeup_softirqd();
445}
446
447void raise_softirq(unsigned int nr)
448{
449 unsigned long flags;
450
451 local_irq_save(flags);
452 raise_softirq_irqoff(nr);
453 local_irq_restore(flags);
454}
455
456void __raise_softirq_irqoff(unsigned int nr)
457{
458 trace_softirq_raise(nr);
459 or_softirq_pending(1UL << nr);
460}
461
462void open_softirq(int nr, void (*action)(struct softirq_action *))
463{
464 softirq_vec[nr].action = action;
465}
466
467/*
468 * Tasklets
469 */
470struct tasklet_head {
471 struct tasklet_struct *head;
472 struct tasklet_struct **tail;
473};
474
475static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
476static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
477
478void __tasklet_schedule(struct tasklet_struct *t)
479{
480 unsigned long flags;
481
482 local_irq_save(flags);
483 t->next = NULL;
484 *__this_cpu_read(tasklet_vec.tail) = t;
485 __this_cpu_write(tasklet_vec.tail, &(t->next));
486 raise_softirq_irqoff(TASKLET_SOFTIRQ);
487 local_irq_restore(flags);
488}
489EXPORT_SYMBOL(__tasklet_schedule);
490
491void __tasklet_hi_schedule(struct tasklet_struct *t)
492{
493 unsigned long flags;
494
495 local_irq_save(flags);
496 t->next = NULL;
497 *__this_cpu_read(tasklet_hi_vec.tail) = t;
498 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
499 raise_softirq_irqoff(HI_SOFTIRQ);
500 local_irq_restore(flags);
501}
502EXPORT_SYMBOL(__tasklet_hi_schedule);
503
504void __tasklet_hi_schedule_first(struct tasklet_struct *t)
505{
506 BUG_ON(!irqs_disabled());
507
508 t->next = __this_cpu_read(tasklet_hi_vec.head);
509 __this_cpu_write(tasklet_hi_vec.head, t);
510 __raise_softirq_irqoff(HI_SOFTIRQ);
511}
512EXPORT_SYMBOL(__tasklet_hi_schedule_first);
513
514static __latent_entropy void tasklet_action(struct softirq_action *a)
515{
516 struct tasklet_struct *list;
517
518 local_irq_disable();
519 list = __this_cpu_read(tasklet_vec.head);
520 __this_cpu_write(tasklet_vec.head, NULL);
521 __this_cpu_write(tasklet_vec.tail, this_cpu_ptr(&tasklet_vec.head));
522 local_irq_enable();
523
524 while (list) {
525 struct tasklet_struct *t = list;
526
527 list = list->next;
528
529 if (tasklet_trylock(t)) {
530 if (!atomic_read(&t->count)) {
531 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
532 &t->state))
533 BUG();
534 t->func(t->data);
535 tasklet_unlock(t);
536 continue;
537 }
538 tasklet_unlock(t);
539 }
540
541 local_irq_disable();
542 t->next = NULL;
543 *__this_cpu_read(tasklet_vec.tail) = t;
544 __this_cpu_write(tasklet_vec.tail, &(t->next));
545 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
546 local_irq_enable();
547 }
548}
549
550static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
551{
552 struct tasklet_struct *list;
553
554 local_irq_disable();
555 list = __this_cpu_read(tasklet_hi_vec.head);
556 __this_cpu_write(tasklet_hi_vec.head, NULL);
557 __this_cpu_write(tasklet_hi_vec.tail, this_cpu_ptr(&tasklet_hi_vec.head));
558 local_irq_enable();
559
560 while (list) {
561 struct tasklet_struct *t = list;
562
563 list = list->next;
564
565 if (tasklet_trylock(t)) {
566 if (!atomic_read(&t->count)) {
567 if (!test_and_clear_bit(TASKLET_STATE_SCHED,
568 &t->state))
569 BUG();
570 t->func(t->data);
571 tasklet_unlock(t);
572 continue;
573 }
574 tasklet_unlock(t);
575 }
576
577 local_irq_disable();
578 t->next = NULL;
579 *__this_cpu_read(tasklet_hi_vec.tail) = t;
580 __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
581 __raise_softirq_irqoff(HI_SOFTIRQ);
582 local_irq_enable();
583 }
584}
585
586void tasklet_init(struct tasklet_struct *t,
587 void (*func)(unsigned long), unsigned long data)
588{
589 t->next = NULL;
590 t->state = 0;
591 atomic_set(&t->count, 0);
592 t->func = func;
593 t->data = data;
594}
595EXPORT_SYMBOL(tasklet_init);
596
597void tasklet_kill(struct tasklet_struct *t)
598{
599 if (in_interrupt())
600 pr_notice("Attempt to kill tasklet from interrupt\n");
601
602 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
603 do {
604 yield();
605 } while (test_bit(TASKLET_STATE_SCHED, &t->state));
606 }
607 tasklet_unlock_wait(t);
608 clear_bit(TASKLET_STATE_SCHED, &t->state);
609}
610EXPORT_SYMBOL(tasklet_kill);
611
612/*
613 * tasklet_hrtimer
614 */
615
616/*
617 * The trampoline is called when the hrtimer expires. It schedules a tasklet
618 * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
619 * hrtimer callback, but from softirq context.
620 */
621static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
622{
623 struct tasklet_hrtimer *ttimer =
624 container_of(timer, struct tasklet_hrtimer, timer);
625
626 tasklet_hi_schedule(&ttimer->tasklet);
627 return HRTIMER_NORESTART;
628}
629
630/*
631 * Helper function which calls the hrtimer callback from
632 * tasklet/softirq context
633 */
634static void __tasklet_hrtimer_trampoline(unsigned long data)
635{
636 struct tasklet_hrtimer *ttimer = (void *)data;
637 enum hrtimer_restart restart;
638
639 restart = ttimer->function(&ttimer->timer);
640 if (restart != HRTIMER_NORESTART)
641 hrtimer_restart(&ttimer->timer);
642}
643
644/**
645 * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
646 * @ttimer: tasklet_hrtimer which is initialized
647 * @function: hrtimer callback function which gets called from softirq context
648 * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
649 * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
650 */
651void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
652 enum hrtimer_restart (*function)(struct hrtimer *),
653 clockid_t which_clock, enum hrtimer_mode mode)
654{
655 hrtimer_init(&ttimer->timer, which_clock, mode);
656 ttimer->timer.function = __hrtimer_tasklet_trampoline;
657 tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
658 (unsigned long)ttimer);
659 ttimer->function = function;
660}
661EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
662
663void __init softirq_init(void)
664{
665 int cpu;
666
667 for_each_possible_cpu(cpu) {
668 per_cpu(tasklet_vec, cpu).tail =
669 &per_cpu(tasklet_vec, cpu).head;
670 per_cpu(tasklet_hi_vec, cpu).tail =
671 &per_cpu(tasklet_hi_vec, cpu).head;
672 }
673
674 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
675 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
676}
677
678static int ksoftirqd_should_run(unsigned int cpu)
679{
680 return local_softirq_pending();
681}
682
683static void run_ksoftirqd(unsigned int cpu)
684{
685 local_irq_disable();
686 if (local_softirq_pending()) {
687 /*
688 * We can safely run softirq on inline stack, as we are not deep
689 * in the task stack here.
690 */
691 __do_softirq();
692 local_irq_enable();
693 cond_resched_rcu_qs();
694 return;
695 }
696 local_irq_enable();
697}
698
699#ifdef CONFIG_HOTPLUG_CPU
700/*
701 * tasklet_kill_immediate is called to remove a tasklet which can already be
702 * scheduled for execution on @cpu.
703 *
704 * Unlike tasklet_kill, this function removes the tasklet
705 * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
706 *
707 * When this function is called, @cpu must be in the CPU_DEAD state.
708 */
709void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
710{
711 struct tasklet_struct **i;
712
713 BUG_ON(cpu_online(cpu));
714 BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
715
716 if (!test_bit(TASKLET_STATE_SCHED, &t->state))
717 return;
718
719 /* CPU is dead, so no lock needed. */
720 for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
721 if (*i == t) {
722 *i = t->next;
723 /* If this was the tail element, move the tail ptr */
724 if (*i == NULL)
725 per_cpu(tasklet_vec, cpu).tail = i;
726 return;
727 }
728 }
729 BUG();
730}
731
732static int takeover_tasklets(unsigned int cpu)
733{
734 /* CPU is dead, so no lock needed. */
735 local_irq_disable();
736
737 /* Find end, append list for that CPU. */
738 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
739 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
740 this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
741 per_cpu(tasklet_vec, cpu).head = NULL;
742 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
743 }
744 raise_softirq_irqoff(TASKLET_SOFTIRQ);
745
746 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
747 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
748 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
749 per_cpu(tasklet_hi_vec, cpu).head = NULL;
750 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
751 }
752 raise_softirq_irqoff(HI_SOFTIRQ);
753
754 local_irq_enable();
755 return 0;
756}
757#else
758#define takeover_tasklets NULL
759#endif /* CONFIG_HOTPLUG_CPU */
760
761static struct smp_hotplug_thread softirq_threads = {
762 .store = &ksoftirqd,
763 .thread_should_run = ksoftirqd_should_run,
764 .thread_fn = run_ksoftirqd,
765 .thread_comm = "ksoftirqd/%u",
766};
767
768static __init int spawn_ksoftirqd(void)
769{
770 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
771 takeover_tasklets);
772 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
773
774 return 0;
775}
776early_initcall(spawn_ksoftirqd);
777
778/*
779 * [ These __weak aliases are kept in a separate compilation unit, so that
780 * GCC does not inline them incorrectly. ]
781 */
782
783int __init __weak early_irq_init(void)
784{
785 return 0;
786}
787
788int __init __weak arch_probe_nr_irqs(void)
789{
790 return NR_IRQS_LEGACY;
791}
792
793int __init __weak arch_early_irq_init(void)
794{
795 return 0;
796}
797
798unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
799{
800 return from;
801}
802
generated by cgit at 2024-05-18 15:45:05 (GMT)