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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_irq());
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#else /* CONFIG_PREEMPT_RT */
298
299/*
300 * This one is for softirq.c-internal use, where hardirqs are disabled
301 * legitimately:
302 */
303#ifdef CONFIG_TRACE_IRQFLAGS
304void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
305{
306 unsigned long flags;
307
308 WARN_ON_ONCE(in_irq());
309
310 raw_local_irq_save(flags);
311 /*
312 * The preempt tracer hooks into preempt_count_add and will break
313 * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
314 * is set and before current->softirq_enabled is cleared.
315 * We must manually increment preempt_count here and manually
316 * call the trace_preempt_off later.
317 */
318 __preempt_count_add(cnt);
319 /*
320 * Were softirqs turned off above:
321 */
322 if (softirq_count() == (cnt & SOFTIRQ_MASK))
323 lockdep_softirqs_off(ip);
324 raw_local_irq_restore(flags);
325
326 if (preempt_count() == cnt) {
327#ifdef CONFIG_DEBUG_PREEMPT
328 current->preempt_disable_ip = get_lock_parent_ip();
329#endif
330 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
331 }
332}
333EXPORT_SYMBOL(__local_bh_disable_ip);
334#endif /* CONFIG_TRACE_IRQFLAGS */
335
336static void __local_bh_enable(unsigned int cnt)
337{
338 lockdep_assert_irqs_disabled();
339
340 if (preempt_count() == cnt)
341 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
342
343 if (softirq_count() == (cnt & SOFTIRQ_MASK))
344 lockdep_softirqs_on(_RET_IP_);
345
346 __preempt_count_sub(cnt);
347}
348
349/*
350 * Special-case - softirqs can safely be enabled by __do_softirq(),
351 * without processing still-pending softirqs:
352 */
353void _local_bh_enable(void)
354{
355 WARN_ON_ONCE(in_irq());
356 __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
357}
358EXPORT_SYMBOL(_local_bh_enable);
359
360void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
361{
362 WARN_ON_ONCE(in_irq());
363 lockdep_assert_irqs_enabled();
364#ifdef CONFIG_TRACE_IRQFLAGS
365 local_irq_disable();
366#endif
367 /*
368 * Are softirqs going to be turned on now:
369 */
370 if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
371 lockdep_softirqs_on(ip);
372 /*
373 * Keep preemption disabled until we are done with
374 * softirq processing:
375 */
376 __preempt_count_sub(cnt - 1);
377
378 if (unlikely(!in_interrupt() && local_softirq_pending())) {
379 /*
380 * Run softirq if any pending. And do it in its own stack
381 * as we may be calling this deep in a task call stack already.
382 */
383 do_softirq();
384 }
385
386 preempt_count_dec();
387#ifdef CONFIG_TRACE_IRQFLAGS
388 local_irq_enable();
389#endif
390 preempt_check_resched();
391}
392EXPORT_SYMBOL(__local_bh_enable_ip);
393
394static inline void softirq_handle_begin(void)
395{
396 __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
397}
398
399static inline void softirq_handle_end(void)
400{
401 __local_bh_enable(SOFTIRQ_OFFSET);
402 WARN_ON_ONCE(in_interrupt());
403}
404
405static inline void ksoftirqd_run_begin(void)
406{
407 local_irq_disable();
408}
409
410static inline void ksoftirqd_run_end(void)
411{
412 local_irq_enable();
413}
414
415static inline bool should_wake_ksoftirqd(void)
416{
417 return true;
418}
419
420static inline void invoke_softirq(void)
421{
422 if (ksoftirqd_running(local_softirq_pending()))
423 return;
424
425 if (!force_irqthreads || !__this_cpu_read(ksoftirqd)) {
426#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
427 /*
428 * We can safely execute softirq on the current stack if
429 * it is the irq stack, because it should be near empty
430 * at this stage.
431 */
432 __do_softirq();
433#else
434 /*
435 * Otherwise, irq_exit() is called on the task stack that can
436 * be potentially deep already. So call softirq in its own stack
437 * to prevent from any overrun.
438 */
439 do_softirq_own_stack();
440#endif
441 } else {
442 wakeup_softirqd();
443 }
444}
445
446asmlinkage __visible void do_softirq(void)
447{
448 __u32 pending;
449 unsigned long flags;
450
451 if (in_interrupt())
452 return;
453
454 local_irq_save(flags);
455
456 pending = local_softirq_pending();
457
458 if (pending && !ksoftirqd_running(pending))
459 do_softirq_own_stack();
460
461 local_irq_restore(flags);
462}
463
464#endif /* !CONFIG_PREEMPT_RT */
465
466/*
467 * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
468 * but break the loop if need_resched() is set or after 2 ms.
469 * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
470 * certain cases, such as stop_machine(), jiffies may cease to
471 * increment and so we need the MAX_SOFTIRQ_RESTART limit as
472 * well to make sure we eventually return from this method.
473 *
474 * These limits have been established via experimentation.
475 * The two things to balance is latency against fairness -
476 * we want to handle softirqs as soon as possible, but they
477 * should not be able to lock up the box.
478 */
479#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
480#define MAX_SOFTIRQ_RESTART 10
481
482#ifdef CONFIG_TRACE_IRQFLAGS
483/*
484 * When we run softirqs from irq_exit() and thus on the hardirq stack we need
485 * to keep the lockdep irq context tracking as tight as possible in order to
486 * not miss-qualify lock contexts and miss possible deadlocks.
487 */
488
489static inline bool lockdep_softirq_start(void)
490{
491 bool in_hardirq = false;
492
493 if (lockdep_hardirq_context()) {
494 in_hardirq = true;
495 lockdep_hardirq_exit();
496 }
497
498 lockdep_softirq_enter();
499
500 return in_hardirq;
501}
502
503static inline void lockdep_softirq_end(bool in_hardirq)
504{
505 lockdep_softirq_exit();
506
507 if (in_hardirq)
508 lockdep_hardirq_enter();
509}
510#else
511static inline bool lockdep_softirq_start(void) { return false; }
512static inline void lockdep_softirq_end(bool in_hardirq) { }
513#endif
514
515asmlinkage __visible void __softirq_entry __do_softirq(void)
516{
517 unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
518 unsigned long old_flags = current->flags;
519 int max_restart = MAX_SOFTIRQ_RESTART;
520 struct softirq_action *h;
521 bool in_hardirq;
522 __u32 pending;
523 int softirq_bit;
524
525 /*
526 * Mask out PF_MEMALLOC as the current task context is borrowed for the
527 * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
528 * again if the socket is related to swapping.
529 */
530 current->flags &= ~PF_MEMALLOC;
531
532 pending = local_softirq_pending();
533
534 softirq_handle_begin();
535 in_hardirq = lockdep_softirq_start();
536 account_softirq_enter(current);
537
538restart:
539 /* Reset the pending bitmask before enabling irqs */
540 set_softirq_pending(0);
541
542 local_irq_enable();
543
544 h = softirq_vec;
545
546 while ((softirq_bit = ffs(pending))) {
547 unsigned int vec_nr;
548 int prev_count;
549
550 h += softirq_bit - 1;
551
552 vec_nr = h - softirq_vec;
553 prev_count = preempt_count();
554
555 kstat_incr_softirqs_this_cpu(vec_nr);
556
557 trace_softirq_entry(vec_nr);
558 h->action(h);
559 trace_softirq_exit(vec_nr);
560 if (unlikely(prev_count != preempt_count())) {
561 pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
562 vec_nr, softirq_to_name[vec_nr], h->action,
563 prev_count, preempt_count());
564 preempt_count_set(prev_count);
565 }
566 h++;
567 pending >>= softirq_bit;
568 }
569
570 if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
571 __this_cpu_read(ksoftirqd) == current)
572 rcu_softirq_qs();
573
574 local_irq_disable();
575
576 pending = local_softirq_pending();
577 if (pending) {
578 if (time_before(jiffies, end) && !need_resched() &&
579 --max_restart)
580 goto restart;
581
582 wakeup_softirqd();
583 }
584
585 account_softirq_exit(current);
586 lockdep_softirq_end(in_hardirq);
587 softirq_handle_end();
588 current_restore_flags(old_flags, PF_MEMALLOC);
589}
590
591/**
592 * irq_enter_rcu - Enter an interrupt context with RCU watching
593 */
594void irq_enter_rcu(void)
595{
596 __irq_enter_raw();
597
598 if (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET))
599 tick_irq_enter();
600
601 account_hardirq_enter(current);
602}
603
604/**
605 * irq_enter - Enter an interrupt context including RCU update
606 */
607void irq_enter(void)
608{
609 rcu_irq_enter();
610 irq_enter_rcu();
611}
612
613static inline void tick_irq_exit(void)
614{
615#ifdef CONFIG_NO_HZ_COMMON
616 int cpu = smp_processor_id();
617
618 /* Make sure that timer wheel updates are propagated */
619 if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
620 if (!in_irq())
621 tick_nohz_irq_exit();
622 }
623#endif
624}
625
626static inline void __irq_exit_rcu(void)
627{
628#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
629 local_irq_disable();
630#else
631 lockdep_assert_irqs_disabled();
632#endif
633 account_hardirq_exit(current);
634 preempt_count_sub(HARDIRQ_OFFSET);
635 if (!in_interrupt() && local_softirq_pending())
636 invoke_softirq();
637
638 tick_irq_exit();
639}
640
641/**
642 * irq_exit_rcu() - Exit an interrupt context without updating RCU
643 *
644 * Also processes softirqs if needed and possible.
645 */
646void irq_exit_rcu(void)
647{
648 __irq_exit_rcu();
649 /* must be last! */
650 lockdep_hardirq_exit();
651}
652
653/**
654 * irq_exit - Exit an interrupt context, update RCU and lockdep
655 *
656 * Also processes softirqs if needed and possible.
657 */
658void irq_exit(void)
659{
660 __irq_exit_rcu();
661 rcu_irq_exit();
662 /* must be last! */
663 lockdep_hardirq_exit();
664}
665
666/*
667 * This function must run with irqs disabled!
668 */
669inline void raise_softirq_irqoff(unsigned int nr)
670{
671 __raise_softirq_irqoff(nr);
672
673 /*
674 * If we're in an interrupt or softirq, we're done
675 * (this also catches softirq-disabled code). We will
676 * actually run the softirq once we return from
677 * the irq or softirq.
678 *
679 * Otherwise we wake up ksoftirqd to make sure we
680 * schedule the softirq soon.
681 */
682 if (!in_interrupt() && should_wake_ksoftirqd())
683 wakeup_softirqd();
684}
685
686void raise_softirq(unsigned int nr)
687{
688 unsigned long flags;
689
690 local_irq_save(flags);
691 raise_softirq_irqoff(nr);
692 local_irq_restore(flags);
693}
694
695void __raise_softirq_irqoff(unsigned int nr)
696{
697 lockdep_assert_irqs_disabled();
698 trace_softirq_raise(nr);
699 or_softirq_pending(1UL << nr);
700}
701
702void open_softirq(int nr, void (*action)(struct softirq_action *))
703{
704 softirq_vec[nr].action = action;
705}
706
707/*
708 * Tasklets
709 */
710struct tasklet_head {
711 struct tasklet_struct *head;
712 struct tasklet_struct **tail;
713};
714
715static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
716static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
717
718static void __tasklet_schedule_common(struct tasklet_struct *t,
719 struct tasklet_head __percpu *headp,
720 unsigned int softirq_nr)
721{
722 struct tasklet_head *head;
723 unsigned long flags;
724
725 local_irq_save(flags);
726 head = this_cpu_ptr(headp);
727 t->next = NULL;
728 *head->tail = t;
729 head->tail = &(t->next);
730 raise_softirq_irqoff(softirq_nr);
731 local_irq_restore(flags);
732}
733
734void __tasklet_schedule(struct tasklet_struct *t)
735{
736 __tasklet_schedule_common(t, &tasklet_vec,
737 TASKLET_SOFTIRQ);
738}
739EXPORT_SYMBOL(__tasklet_schedule);
740
741void __tasklet_hi_schedule(struct tasklet_struct *t)
742{
743 __tasklet_schedule_common(t, &tasklet_hi_vec,
744 HI_SOFTIRQ);
745}
746EXPORT_SYMBOL(__tasklet_hi_schedule);
747
748static bool tasklet_clear_sched(struct tasklet_struct *t)
749{
750 if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
751 wake_up_var(&t->state);
752 return true;
753 }
754
755 WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
756 t->use_callback ? "callback" : "func",
757 t->use_callback ? (void *)t->callback : (void *)t->func);
758
759 return false;
760}
761
762static void tasklet_action_common(struct softirq_action *a,
763 struct tasklet_head *tl_head,
764 unsigned int softirq_nr)
765{
766 struct tasklet_struct *list;
767
768 local_irq_disable();
769 list = tl_head->head;
770 tl_head->head = NULL;
771 tl_head->tail = &tl_head->head;
772 local_irq_enable();
773
774 while (list) {
775 struct tasklet_struct *t = list;
776
777 list = list->next;
778
779 if (tasklet_trylock(t)) {
780 if (!atomic_read(&t->count)) {
781 if (tasklet_clear_sched(t)) {
782 if (t->use_callback)
783 t->callback(t);
784 else
785 t->func(t->data);
786 }
787 tasklet_unlock(t);
788 continue;
789 }
790 tasklet_unlock(t);
791 }
792
793 local_irq_disable();
794 t->next = NULL;
795 *tl_head->tail = t;
796 tl_head->tail = &t->next;
797 __raise_softirq_irqoff(softirq_nr);
798 local_irq_enable();
799 }
800}
801
802static __latent_entropy void tasklet_action(struct softirq_action *a)
803{
804 tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
805}
806
807static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
808{
809 tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
810}
811
812void tasklet_setup(struct tasklet_struct *t,
813 void (*callback)(struct tasklet_struct *))
814{
815 t->next = NULL;
816 t->state = 0;
817 atomic_set(&t->count, 0);
818 t->callback = callback;
819 t->use_callback = true;
820 t->data = 0;
821}
822EXPORT_SYMBOL(tasklet_setup);
823
824void tasklet_init(struct tasklet_struct *t,
825 void (*func)(unsigned long), unsigned long data)
826{
827 t->next = NULL;
828 t->state = 0;
829 atomic_set(&t->count, 0);
830 t->func = func;
831 t->use_callback = false;
832 t->data = data;
833}
834EXPORT_SYMBOL(tasklet_init);
835
836#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
837/*
838 * Do not use in new code. Waiting for tasklets from atomic contexts is
839 * error prone and should be avoided.
840 */
841void tasklet_unlock_spin_wait(struct tasklet_struct *t)
842{
843 while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
844 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
845 /*
846 * Prevent a live lock when current preempted soft
847 * interrupt processing or prevents ksoftirqd from
848 * running. If the tasklet runs on a different CPU
849 * then this has no effect other than doing the BH
850 * disable/enable dance for nothing.
851 */
852 local_bh_disable();
853 local_bh_enable();
854 } else {
855 cpu_relax();
856 }
857 }
858}
859EXPORT_SYMBOL(tasklet_unlock_spin_wait);
860#endif
861
862void tasklet_kill(struct tasklet_struct *t)
863{
864 if (in_interrupt())
865 pr_notice("Attempt to kill tasklet from interrupt\n");
866
867 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
868 wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
869
870 tasklet_unlock_wait(t);
871 tasklet_clear_sched(t);
872}
873EXPORT_SYMBOL(tasklet_kill);
874
875#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
876void tasklet_unlock(struct tasklet_struct *t)
877{
878 smp_mb__before_atomic();
879 clear_bit(TASKLET_STATE_RUN, &t->state);
880 smp_mb__after_atomic();
881 wake_up_var(&t->state);
882}
883EXPORT_SYMBOL_GPL(tasklet_unlock);
884
885void tasklet_unlock_wait(struct tasklet_struct *t)
886{
887 wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
888}
889EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
890#endif
891
892void __init softirq_init(void)
893{
894 int cpu;
895
896 for_each_possible_cpu(cpu) {
897 per_cpu(tasklet_vec, cpu).tail =
898 &per_cpu(tasklet_vec, cpu).head;
899 per_cpu(tasklet_hi_vec, cpu).tail =
900 &per_cpu(tasklet_hi_vec, cpu).head;
901 }
902
903 open_softirq(TASKLET_SOFTIRQ, tasklet_action);
904 open_softirq(HI_SOFTIRQ, tasklet_hi_action);
905}
906
907static int ksoftirqd_should_run(unsigned int cpu)
908{
909 return local_softirq_pending();
910}
911
912static void run_ksoftirqd(unsigned int cpu)
913{
914 ksoftirqd_run_begin();
915 if (local_softirq_pending()) {
916 /*
917 * We can safely run softirq on inline stack, as we are not deep
918 * in the task stack here.
919 */
920 __do_softirq();
921 ksoftirqd_run_end();
922 cond_resched();
923 return;
924 }
925 ksoftirqd_run_end();
926}
927
928#ifdef CONFIG_HOTPLUG_CPU
929static int takeover_tasklets(unsigned int cpu)
930{
931 /* CPU is dead, so no lock needed. */
932 local_irq_disable();
933
934 /* Find end, append list for that CPU. */
935 if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
936 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
937 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
938 per_cpu(tasklet_vec, cpu).head = NULL;
939 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
940 }
941 raise_softirq_irqoff(TASKLET_SOFTIRQ);
942
943 if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
944 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
945 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
946 per_cpu(tasklet_hi_vec, cpu).head = NULL;
947 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
948 }
949 raise_softirq_irqoff(HI_SOFTIRQ);
950
951 local_irq_enable();
952 return 0;
953}
954#else
955#define takeover_tasklets NULL
956#endif /* CONFIG_HOTPLUG_CPU */
957
958static struct smp_hotplug_thread softirq_threads = {
959 .store = &ksoftirqd,
960 .thread_should_run = ksoftirqd_should_run,
961 .thread_fn = run_ksoftirqd,
962 .thread_comm = "ksoftirqd/%u",
963};
964
965static __init int spawn_ksoftirqd(void)
966{
967 cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
968 takeover_tasklets);
969 BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
970
971 return 0;
972}
973early_initcall(spawn_ksoftirqd);
974
975/*
976 * [ These __weak aliases are kept in a separate compilation unit, so that
977 * GCC does not inline them incorrectly. ]
978 */
979
980int __init __weak early_irq_init(void)
981{
982 return 0;
983}
984
985int __init __weak arch_probe_nr_irqs(void)
986{
987 return NR_IRQS_LEGACY;
988}
989
990int __init __weak arch_early_irq_init(void)
991{
992 return 0;
993}
994
995unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
996{
997 return from;
998}
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}