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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// 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#ifdef CONFIG_TRACE_IRQFLAGS
84DEFINE_PER_CPU(int, hardirqs_enabled);
85DEFINE_PER_CPU(int, hardirq_context);
86EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled);
87EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context);
88#endif
89
90/*
91 * SOFTIRQ_OFFSET usage:
92 *
93 * On !RT kernels 'count' is the preempt counter, on RT kernels this applies
94 * to a per CPU counter and to task::softirqs_disabled_cnt.
95 *
96 * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq
97 * processing.
98 *
99 * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
100 * on local_bh_disable or local_bh_enable.
101 *
102 * This lets us distinguish between whether we are currently processing
103 * softirq and whether we just have bh disabled.
104 */
105#ifdef CONFIG_PREEMPT_RT
106
107/*
108 * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and
109 * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a
110 * softirq disabled section to be preempted.
111 *
112 * The per task counter is used for softirq_count(), in_softirq() and
113 * in_serving_softirqs() because these counts are only valid when the task
114 * holding softirq_ctrl::lock is running.
115 *
116 * The per CPU counter prevents pointless wakeups of ksoftirqd in case that
117 * the task which is in a softirq disabled section is preempted or blocks.
118 */
119struct softirq_ctrl {
120 local_lock_t lock;
121 int cnt;
122};
123
124static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = {
125 .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock),
126};
127
128/**
129 * local_bh_blocked() - Check for idle whether BH processing is blocked
130 *
131 * Returns false if the per CPU softirq::cnt is 0 otherwise true.
132 *
133 * This is invoked from the idle task to guard against false positive
134 * softirq pending warnings, which would happen when the task which holds
135 * softirq_ctrl::lock was the only running task on the CPU and blocks on
136 * some other lock.
137 */
138bool local_bh_blocked(void)
139{
140 return __this_cpu_read(softirq_ctrl.cnt) != 0;
141}
142
143void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
144{
145 unsigned long flags;
146 int newcnt;
147
148 WARN_ON_ONCE(in_hardirq());
149
150 /* First entry of a task into a BH disabled section? */
151 if (!current->softirq_disable_cnt) {
152 if (preemptible()) {
153 local_lock(&softirq_ctrl.lock);
154 /* Required to meet the RCU bottomhalf requirements. */
155 rcu_read_lock();
156 } else {
157 DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt));
158 }
159 }
160
161 /*
162 * Track the per CPU softirq disabled state. On RT this is per CPU
163 * state to allow preemption of bottom half disabled sections.
164 */
165 newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt);
166 /*
167 * Reflect the result in the task state to prevent recursion on the
168 * local lock and to make softirq_count() & al work.
169 */
170 current->softirq_disable_cnt = newcnt;
171
172 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) {
173 raw_local_irq_save(flags);
174 lockdep_softirqs_off(ip);
175 raw_local_irq_restore(flags);
176 }
177}
178EXPORT_SYMBOL(__local_bh_disable_ip);
179
180static void __local_bh_enable(unsigned int cnt, bool unlock)
181{
182 unsigned long flags;
183 int newcnt;
184
185 DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=
186 this_cpu_read(softirq_ctrl.cnt));
187
188 if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) {
189 raw_local_irq_save(flags);
190 lockdep_softirqs_on(_RET_IP_);
191 raw_local_irq_restore(flags);
192 }
193
194 newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt);
195 current->softirq_disable_cnt = newcnt;
196
197 if (!newcnt && unlock) {
198 rcu_read_unlock();
199 local_unlock(&softirq_ctrl.lock);
200 }
201}
202
203void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
204{
205 bool preempt_on = preemptible();
206 unsigned long flags;
207 u32 pending;
208 int curcnt;
209
210 WARN_ON_ONCE(in_hardirq());
211 lockdep_assert_irqs_enabled();
212
213 local_irq_save(flags);
214 curcnt = __this_cpu_read(softirq_ctrl.cnt);
215
216 /*
217 * If this is not reenabling soft interrupts, no point in trying to
218 * run pending ones.
219 */
220 if (curcnt != cnt)
221 goto out;
222
223 pending = local_softirq_pending();
224 if (!pending)
225 goto out;
226
227 /*
228 * If this was called from non preemptible context, wake up the
229 * softirq daemon.
230 */
231 if (!preempt_on) {
232 wakeup_softirqd();
233 goto out;
234 }
235
236 /*
237 * Adjust softirq count to SOFTIRQ_OFFSET which makes
238 * in_serving_softirq() become true.
239 */
240 cnt = SOFTIRQ_OFFSET;
241 __local_bh_enable(cnt, false);
242 __do_softirq();
243
244out:
245 __local_bh_enable(cnt, preempt_on);
246 local_irq_restore(flags);
247}
248EXPORT_SYMBOL(__local_bh_enable_ip);
249
250/*
251 * Invoked from ksoftirqd_run() outside of the interrupt disabled section
252 * to acquire the per CPU local lock for reentrancy protection.
253 */
254static inline void ksoftirqd_run_begin(void)
255{
256 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
257 local_irq_disable();
258}
259
260/* Counterpart to ksoftirqd_run_begin() */
261static inline void ksoftirqd_run_end(void)
262{
263 __local_bh_enable(SOFTIRQ_OFFSET, true);
264 WARN_ON_ONCE(in_interrupt());
265 local_irq_enable();
266}
267
268static inline void softirq_handle_begin(void) { }
269static inline void softirq_handle_end(void) { }
270
271static inline bool should_wake_ksoftirqd(void)
272{
273 return !this_cpu_read(softirq_ctrl.cnt);
274}
275
276static inline void invoke_softirq(void)
277{
278 if (should_wake_ksoftirqd())
279 wakeup_softirqd();
280}
281
282/*
283 * flush_smp_call_function_queue() can raise a soft interrupt in a function
284 * call. On RT kernels this is undesired and the only known functionality
285 * in the block layer which does this is disabled on RT. If soft interrupts
286 * get raised which haven't been raised before the flush, warn so it can be
287 * investigated.
288 */
289void do_softirq_post_smp_call_flush(unsigned int was_pending)
290{
291 if (WARN_ON_ONCE(was_pending != local_softirq_pending()))
292 invoke_softirq();
293}
294
295#else /* CONFIG_PREEMPT_RT */
296
297/*
298 * This one is for softirq.c-internal use, where hardirqs are disabled
299 * legitimately:
300 */
301#ifdef CONFIG_TRACE_IRQFLAGS
302void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
303{
304 unsigned long flags;
305
306 WARN_ON_ONCE(in_hardirq());
307
308 raw_local_irq_save(flags);
309 /*
310 * The preempt tracer hooks into preempt_count_add and will break
311 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
312 * is set and before current->softirq_enabled is cleared.
313 * We must manually increment preempt_count here and manually
314 * call the trace_preempt_off later.
315 */
316 __preempt_count_add(cnt);
317 /*
318 * Were softirqs turned off above:
319 */
320 if (softirq_count() == (cnt & SOFTIRQ_MASK))
321 lockdep_softirqs_off(ip);
322 raw_local_irq_restore(flags);
323
324 if (preempt_count() == cnt) {
325#ifdef CONFIG_DEBUG_PREEMPT
326 current->preempt_disable_ip = get_lock_parent_ip();
327#endif
328 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
329 }
330}
331EXPORT_SYMBOL(__local_bh_disable_ip);
332#endif /* CONFIG_TRACE_IRQFLAGS */
333
334static void __local_bh_enable(unsigned int cnt)
335{
336 lockdep_assert_irqs_disabled();
337
338 if (preempt_count() == cnt)
339 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
340
341 if (softirq_count() == (cnt & SOFTIRQ_MASK))
342 lockdep_softirqs_on(_RET_IP_);
343
344 __preempt_count_sub(cnt);
345}
346
347/*
348 * Special-case - softirqs can safely be enabled by __do_softirq(),
349 * without processing still-pending softirqs:
350 */
351void _local_bh_enable(void)
352{
353 WARN_ON_ONCE(in_hardirq());
354 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
355}
356EXPORT_SYMBOL(_local_bh_enable);
357
358void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
359{
360 WARN_ON_ONCE(in_hardirq());
361 lockdep_assert_irqs_enabled();
362#ifdef CONFIG_TRACE_IRQFLAGS
363 local_irq_disable();
364#endif
365 /*
366 * Are softirqs going to be turned on now:
367 */
368 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
369 lockdep_softirqs_on(ip);
370 /*
371 * Keep preemption disabled until we are done with
372 * softirq processing:
373 */
374 __preempt_count_sub(cnt - 1);
375
376 if (unlikely(!in_interrupt() && local_softirq_pending())) {
377 /*
378 * Run softirq if any pending. And do it in its own stack
379 * as we may be calling this deep in a task call stack already.
380 */
381 do_softirq();
382 }
383
384 preempt_count_dec();
385#ifdef CONFIG_TRACE_IRQFLAGS
386 local_irq_enable();
387#endif
388 preempt_check_resched();
389}
390EXPORT_SYMBOL(__local_bh_enable_ip);
391
392static inline void softirq_handle_begin(void)
393{
394 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
395}
396
397static inline void softirq_handle_end(void)
398{
399 __local_bh_enable(SOFTIRQ_OFFSET);
400 WARN_ON_ONCE(in_interrupt());
401}
402
403static inline void ksoftirqd_run_begin(void)
404{
405 local_irq_disable();
406}
407
408static inline void ksoftirqd_run_end(void)
409{
410 local_irq_enable();
411}
412
413static inline bool should_wake_ksoftirqd(void)
414{
415 return true;
416}
417
418static inline void invoke_softirq(void)
419{
420 if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
421#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
422 /*
423 * We can safely execute softirq on the current stack if
424 * it is the irq stack, because it should be near empty
425 * at this stage.
426 */
427 __do_softirq();
428#else
429 /*
430 * Otherwise, irq_exit() is called on the task stack that can
431 * be potentially deep already. So call softirq in its own stack
432 * to prevent from any overrun.
433 */
434 do_softirq_own_stack();
435#endif
436 } else {
437 wakeup_softirqd();
438 }
439}
440
441asmlinkage __visible void do_softirq(void)
442{
443 __u32 pending;
444 unsigned long flags;
445
446 if (in_interrupt())
447 return;
448
449 local_irq_save(flags);
450
451 pending = local_softirq_pending();
452
453 if (pending)
454 do_softirq_own_stack();
455
456 local_irq_restore(flags);
457}
458
459#endif /* !CONFIG_PREEMPT_RT */
460
461/*
462 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
463 * but break the loop if need_resched() is set or after 2 ms.
464 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
465 * certain cases, such as stop_machine(), jiffies may cease to
466 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
467 * well to make sure we eventually return from this method.
468 *
469 * These limits have been established via experimentation.
470 * The two things to balance is latency against fairness -
471 * we want to handle softirqs as soon as possible, but they
472 * should not be able to lock up the box.
473 */
474#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
475#define MAX_SOFTIRQ_RESTART 10
476
477#ifdef CONFIG_TRACE_IRQFLAGS
478/*
479 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
480 * to keep the lockdep irq context tracking as tight as possible in order to
481 * not miss-qualify lock contexts and miss possible deadlocks.
482 */
483
484static inline bool lockdep_softirq_start(void)
485{
486 bool in_hardirq = false;
487
488 if (lockdep_hardirq_context()) {
489 in_hardirq = true;
490 lockdep_hardirq_exit();
491 }
492
493 lockdep_softirq_enter();
494
495 return in_hardirq;
496}
497
498static inline void lockdep_softirq_end(bool in_hardirq)
499{
500 lockdep_softirq_exit();
501
502 if (in_hardirq)
503 lockdep_hardirq_enter();
504}
505#else
506static inline bool lockdep_softirq_start(void) { return false; }
507static inline void lockdep_softirq_end(bool in_hardirq) { }
508#endif
509
510asmlinkage __visible void __softirq_entry __do_softirq(void)
511{
512 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
513 unsigned long old_flags = current->flags;
514 int max_restart = MAX_SOFTIRQ_RESTART;
515 struct softirq_action *h;
516 bool in_hardirq;
517 __u32 pending;
518 int softirq_bit;
519
520 /*
521 * Mask out PF_MEMALLOC as the current task context is borrowed for the
522 * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
523 * again if the socket is related to swapping.
524 */
525 current->flags &= ~PF_MEMALLOC;
526
527 pending = local_softirq_pending();
528
529 softirq_handle_begin();
530 in_hardirq = lockdep_softirq_start();
531 account_softirq_enter(current);
532
533restart:
534 /* Reset the pending bitmask before enabling irqs */
535 set_softirq_pending(0);
536
537 local_irq_enable();
538
539 h = softirq_vec;
540
541 while ((softirq_bit = ffs(pending))) {
542 unsigned int vec_nr;
543 int prev_count;
544
545 h += softirq_bit - 1;
546
547 vec_nr = h - softirq_vec;
548 prev_count = preempt_count();
549
550 kstat_incr_softirqs_this_cpu(vec_nr);
551
552 trace_softirq_entry(vec_nr);
553 h->action(h);
554 trace_softirq_exit(vec_nr);
555 if (unlikely(prev_count != preempt_count())) {
556 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
557 vec_nr, softirq_to_name[vec_nr], h->action,
558 prev_count, preempt_count());
559 preempt_count_set(prev_count);
560 }
561 h++;
562 pending >>= softirq_bit;
563 }
564
565 if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
566 __this_cpu_read(ksoftirqd) == current)
567 rcu_softirq_qs();
568
569 local_irq_disable();
570
571 pending = local_softirq_pending();
572 if (pending) {
573 if (time_before(jiffies, end) && !need_resched() &&
574 --max_restart)
575 goto restart;
576
577 wakeup_softirqd();
578 }
579
580 account_softirq_exit(current);
581 lockdep_softirq_end(in_hardirq);
582 softirq_handle_end();
583 current_restore_flags(old_flags, PF_MEMALLOC);
584}
585
586/**
587 * irq_enter_rcu - Enter an interrupt context with RCU watching
588 */
589void irq_enter_rcu(void)
590{
591 __irq_enter_raw();
592
593 if (tick_nohz_full_cpu(smp_processor_id()) ||
594 (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)))
595 tick_irq_enter();
596
597 account_hardirq_enter(current);
598}
599
600/**
601 * irq_enter - Enter an interrupt context including RCU update
602 */
603void irq_enter(void)
604{
605 ct_irq_enter();
606 irq_enter_rcu();
607}
608
609static inline void tick_irq_exit(void)
610{
611#ifdef CONFIG_NO_HZ_COMMON
612 int cpu = smp_processor_id();
613
614 /* Make sure that timer wheel updates are propagated */
615 if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
616 if (!in_hardirq())
617 tick_nohz_irq_exit();
618 }
619#endif
620}
621
622static inline void __irq_exit_rcu(void)
623{
624#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
625 local_irq_disable();
626#else
627 lockdep_assert_irqs_disabled();
628#endif
629 account_hardirq_exit(current);
630 preempt_count_sub(HARDIRQ_OFFSET);
631 if (!in_interrupt() && local_softirq_pending())
632 invoke_softirq();
633
634 tick_irq_exit();
635}
636
637/**
638 * irq_exit_rcu() - Exit an interrupt context without updating RCU
639 *
640 * Also processes softirqs if needed and possible.
641 */
642void irq_exit_rcu(void)
643{
644 __irq_exit_rcu();
645 /* must be last! */
646 lockdep_hardirq_exit();
647}
648
649/**
650 * irq_exit - Exit an interrupt context, update RCU and lockdep
651 *
652 * Also processes softirqs if needed and possible.
653 */
654void irq_exit(void)
655{
656 __irq_exit_rcu();
657 ct_irq_exit();
658 /* must be last! */
659 lockdep_hardirq_exit();
660}
661
662/*
663 * This function must run with irqs disabled!
664 */
665inline void raise_softirq_irqoff(unsigned int nr)
666{
667 __raise_softirq_irqoff(nr);
668
669 /*
670 * If we're in an interrupt or softirq, we're done
671 * (this also catches softirq-disabled code). We will
672 * actually run the softirq once we return from
673 * the irq or softirq.
674 *
675 * Otherwise we wake up ksoftirqd to make sure we
676 * schedule the softirq soon.
677 */
678 if (!in_interrupt() && should_wake_ksoftirqd())
679 wakeup_softirqd();
680}
681
682void raise_softirq(unsigned int nr)
683{
684 unsigned long flags;
685
686 local_irq_save(flags);
687 raise_softirq_irqoff(nr);
688 local_irq_restore(flags);
689}
690
691void __raise_softirq_irqoff(unsigned int nr)
692{
693 lockdep_assert_irqs_disabled();
694 trace_softirq_raise(nr);
695 or_softirq_pending(1UL << nr);
696}
697
698void open_softirq(int nr, void (*action)(struct softirq_action *))
699{
700 softirq_vec[nr].action = action;
701}
702
703/*
704 * Tasklets
705 */
706struct tasklet_head {
707 struct tasklet_struct *head;
708 struct tasklet_struct **tail;
709};
710
711static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
712static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
713
714static void __tasklet_schedule_common(struct tasklet_struct *t,
715 struct tasklet_head __percpu *headp,
716 unsigned int softirq_nr)
717{
718 struct tasklet_head *head;
719 unsigned long flags;
720
721 local_irq_save(flags);
722 head = this_cpu_ptr(headp);
723 t->next = NULL;
724 *head->tail = t;
725 head->tail = &(t->next);
726 raise_softirq_irqoff(softirq_nr);
727 local_irq_restore(flags);
728}
729
730void __tasklet_schedule(struct tasklet_struct *t)
731{
732 __tasklet_schedule_common(t, &tasklet_vec,
733 TASKLET_SOFTIRQ);
734}
735EXPORT_SYMBOL(__tasklet_schedule);
736
737void __tasklet_hi_schedule(struct tasklet_struct *t)
738{
739 __tasklet_schedule_common(t, &tasklet_hi_vec,
740 HI_SOFTIRQ);
741}
742EXPORT_SYMBOL(__tasklet_hi_schedule);
743
744static bool tasklet_clear_sched(struct tasklet_struct *t)
745{
746 if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
747 wake_up_var(&t->state);
748 return true;
749 }
750
751 WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
752 t->use_callback ? "callback" : "func",
753 t->use_callback ? (void *)t->callback : (void *)t->func);
754
755 return false;
756}
757
758static void tasklet_action_common(struct softirq_action *a,
759 struct tasklet_head *tl_head,
760 unsigned int softirq_nr)
761{
762 struct tasklet_struct *list;
763
764 local_irq_disable();
765 list = tl_head->head;
766 tl_head->head = NULL;
767 tl_head->tail = &tl_head->head;
768 local_irq_enable();
769
770 while (list) {
771 struct tasklet_struct *t = list;
772
773 list = list->next;
774
775 if (tasklet_trylock(t)) {
776 if (!atomic_read(&t->count)) {
777 if (tasklet_clear_sched(t)) {
778 if (t->use_callback) {
779 trace_tasklet_entry(t, t->callback);
780 t->callback(t);
781 trace_tasklet_exit(t, t->callback);
782 } else {
783 trace_tasklet_entry(t, t->func);
784 t->func(t->data);
785 trace_tasklet_exit(t, t->func);
786 }
787 }
788 tasklet_unlock(t);
789 continue;
790 }
791 tasklet_unlock(t);
792 }
793
794 local_irq_disable();
795 t->next = NULL;
796 *tl_head->tail = t;
797 tl_head->tail = &t->next;
798 __raise_softirq_irqoff(softirq_nr);
799 local_irq_enable();
800 }
801}
802
803static __latent_entropy void tasklet_action(struct softirq_action *a)
804{
805 tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
806}
807
808static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
809{
810 tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
811}
812
813void tasklet_setup(struct tasklet_struct *t,
814 void (*callback)(struct tasklet_struct *))
815{
816 t->next = NULL;
817 t->state = 0;
818 atomic_set(&t->count, 0);
819 t->callback = callback;
820 t->use_callback = true;
821 t->data = 0;
822}
823EXPORT_SYMBOL(tasklet_setup);
824
825void tasklet_init(struct tasklet_struct *t,
826 void (*func)(unsigned long), unsigned long data)
827{
828 t->next = NULL;
829 t->state = 0;
830 atomic_set(&t->count, 0);
831 t->func = func;
832 t->use_callback = false;
833 t->data = data;
834}
835EXPORT_SYMBOL(tasklet_init);
836
837#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
838/*
839 * Do not use in new code. Waiting for tasklets from atomic contexts is
840 * error prone and should be avoided.
841 */
842void tasklet_unlock_spin_wait(struct tasklet_struct *t)
843{
844 while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
845 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
846 /*
847 * Prevent a live lock when current preempted soft
848 * interrupt processing or prevents ksoftirqd from
849 * running. If the tasklet runs on a different CPU
850 * then this has no effect other than doing the BH
851 * disable/enable dance for nothing.
852 */
853 local_bh_disable();
854 local_bh_enable();
855 } else {
856 cpu_relax();
857 }
858 }
859}
860EXPORT_SYMBOL(tasklet_unlock_spin_wait);
861#endif
862
863void tasklet_kill(struct tasklet_struct *t)
864{
865 if (in_interrupt())
866 pr_notice("Attempt to kill tasklet from interrupt\n");
867
868 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
869 wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
870
871 tasklet_unlock_wait(t);
872 tasklet_clear_sched(t);
873}
874EXPORT_SYMBOL(tasklet_kill);
875
876#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
877void tasklet_unlock(struct tasklet_struct *t)
878{
879 smp_mb__before_atomic();
880 clear_bit(TASKLET_STATE_RUN, &t->state);
881 smp_mb__after_atomic();
882 wake_up_var(&t->state);
883}
884EXPORT_SYMBOL_GPL(tasklet_unlock);
885
886void tasklet_unlock_wait(struct tasklet_struct *t)
887{
888 wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
889}
890EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
891#endif
892
893void __init softirq_init(void)
894{
895 int cpu;
896
897 for_each_possible_cpu(cpu) {
898 per_cpu(tasklet_vec, cpu).tail =
899 &per_cpu(tasklet_vec, cpu).head;
900 per_cpu(tasklet_hi_vec, cpu).tail =
901 &per_cpu(tasklet_hi_vec, cpu).head;
902 }
903
904 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
905 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
906}
907
908static int ksoftirqd_should_run(unsigned int cpu)
909{
910 return local_softirq_pending();
911}
912
913static void run_ksoftirqd(unsigned int cpu)
914{
915 ksoftirqd_run_begin();
916 if (local_softirq_pending()) {
917 /*
918 * We can safely run softirq on inline stack, as we are not deep
919 * in the task stack here.
920 */
921 __do_softirq();
922 ksoftirqd_run_end();
923 cond_resched();
924 return;
925 }
926 ksoftirqd_run_end();
927}
928
929#ifdef CONFIG_HOTPLUG_CPU
930static int takeover_tasklets(unsigned int cpu)
931{
932 /* CPU is dead, so no lock needed. */
933 local_irq_disable();
934
935 /* Find end, append list for that CPU. */
936 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
937 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
938 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
939 per_cpu(tasklet_vec, cpu).head = NULL;
940 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
941 }
942 raise_softirq_irqoff(TASKLET_SOFTIRQ);
943
944 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
945 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
946 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
947 per_cpu(tasklet_hi_vec, cpu).head = NULL;
948 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
949 }
950 raise_softirq_irqoff(HI_SOFTIRQ);
951
952 local_irq_enable();
953 return 0;
954}
955#else
956#define takeover_tasklets NULL
957#endif /* CONFIG_HOTPLUG_CPU */
958
959static struct smp_hotplug_thread softirq_threads = {
960 .store = &ksoftirqd,
961 .thread_should_run = ksoftirqd_should_run,
962 .thread_fn = run_ksoftirqd,
963 .thread_comm = "ksoftirqd/%u",
964};
965
966static __init int spawn_ksoftirqd(void)
967{
968 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
969 takeover_tasklets);
970 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
971
972 return 0;
973}
974early_initcall(spawn_ksoftirqd);
975
976/*
977 * [ These __weak aliases are kept in a separate compilation unit, so that
978 * GCC does not inline them incorrectly. ]
979 */
980
981int __init __weak early_irq_init(void)
982{
983 return 0;
984}
985
986int __init __weak arch_probe_nr_irqs(void)
987{
988 return NR_IRQS_LEGACY;
989}
990
991int __init __weak arch_early_irq_init(void)
992{
993 return 0;
994}
995
996unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
997{
998 return from;
999}