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