Line data Source code
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
55 : DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat);
56 : EXPORT_PER_CPU_SYMBOL(irq_stat);
57 : #endif
58 :
59 : static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
60 :
61 : DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
62 :
63 : const 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 : */
74 : static void wakeup_softirqd(void)
75 : {
76 : /* Interrupts are disabled: no need to stop preemption */
77 666 : struct task_struct *tsk = __this_cpu_read(ksoftirqd);
78 :
79 666 : if (tsk)
80 666 : 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))
89 88 : static bool ksoftirqd_running(unsigned long pending)
90 : {
91 88 : struct task_struct *tsk = __this_cpu_read(ksoftirqd);
92 :
93 88 : if (pending & SOFTIRQ_NOW_MASK)
94 : return false;
95 88 : return tsk && task_is_running(tsk) && !__kthread_should_park(tsk);
96 : }
97 :
98 : #ifdef CONFIG_TRACE_IRQFLAGS
99 : DEFINE_PER_CPU(int, hardirqs_enabled);
100 : DEFINE_PER_CPU(int, hardirq_context);
101 : EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled);
102 : EXPORT_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 : */
134 : struct softirq_ctrl {
135 : local_lock_t lock;
136 : int cnt;
137 : };
138 :
139 : static 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 : */
153 : bool local_bh_blocked(void)
154 : {
155 : return __this_cpu_read(softirq_ctrl.cnt) != 0;
156 : }
157 :
158 : void __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 : }
193 : EXPORT_SYMBOL(__local_bh_disable_ip);
194 :
195 : static 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 :
218 : void __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 :
259 : out:
260 : __local_bh_enable(cnt, preempt_on);
261 : local_irq_restore(flags);
262 : }
263 : EXPORT_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 : */
269 : static 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() */
276 : static 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 :
283 : static inline void softirq_handle_begin(void) { }
284 : static inline void softirq_handle_end(void) { }
285 :
286 : static inline bool should_wake_ksoftirqd(void)
287 : {
288 : return !this_cpu_read(softirq_ctrl.cnt);
289 : }
290 :
291 : static 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 : */
304 : void 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
317 : void __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 : }
346 : EXPORT_SYMBOL(__local_bh_disable_ip);
347 : #endif /* CONFIG_TRACE_IRQFLAGS */
348 :
349 : static 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 :
356 429 : if (softirq_count() == (cnt & SOFTIRQ_MASK))
357 429 : lockdep_softirqs_on(_RET_IP_);
358 :
359 858 : __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 : */
366 0 : void _local_bh_enable(void)
367 : {
368 0 : WARN_ON_ONCE(in_hardirq());
369 0 : __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
370 0 : }
371 : EXPORT_SYMBOL(_local_bh_enable);
372 :
373 1666 : void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
374 : {
375 1666 : 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 3332 : __preempt_count_sub(cnt - 1);
390 :
391 1666 : 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 0 : do_softirq();
397 : }
398 :
399 1666 : preempt_count_dec();
400 : #ifdef CONFIG_TRACE_IRQFLAGS
401 : local_irq_enable();
402 : #endif
403 : preempt_check_resched();
404 1666 : }
405 : EXPORT_SYMBOL(__local_bh_enable_ip);
406 :
407 : static inline void softirq_handle_begin(void)
408 : {
409 858 : __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
410 : }
411 :
412 429 : static inline void softirq_handle_end(void)
413 : {
414 429 : __local_bh_enable(SOFTIRQ_OFFSET);
415 429 : WARN_ON_ONCE(in_interrupt());
416 429 : }
417 :
418 : static inline void ksoftirqd_run_begin(void)
419 : {
420 : local_irq_disable();
421 : }
422 :
423 : static inline void ksoftirqd_run_end(void)
424 : {
425 : local_irq_enable();
426 : }
427 :
428 : static inline bool should_wake_ksoftirqd(void)
429 : {
430 : return true;
431 : }
432 :
433 88 : static inline void invoke_softirq(void)
434 : {
435 88 : 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 :
459 0 : asmlinkage __visible void do_softirq(void)
460 : {
461 : __u32 pending;
462 : unsigned long flags;
463 :
464 0 : if (in_interrupt())
465 : return;
466 :
467 0 : local_irq_save(flags);
468 :
469 0 : pending = local_softirq_pending();
470 :
471 0 : if (pending && !ksoftirqd_running(pending))
472 : do_softirq_own_stack();
473 :
474 0 : 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 :
502 : static 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 :
516 : static 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
524 : static inline bool lockdep_softirq_start(void) { return false; }
525 : static inline void lockdep_softirq_end(bool in_hardirq) { }
526 : #endif
527 :
528 429 : asmlinkage __visible void __softirq_entry __do_softirq(void)
529 : {
530 429 : unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
531 429 : unsigned long old_flags = current->flags;
532 429 : 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 : */
543 429 : current->flags &= ~PF_MEMALLOC;
544 :
545 429 : pending = local_softirq_pending();
546 :
547 429 : softirq_handle_begin();
548 429 : in_hardirq = lockdep_softirq_start();
549 429 : account_softirq_enter(current);
550 :
551 : restart:
552 : /* Reset the pending bitmask before enabling irqs */
553 754 : set_softirq_pending(0);
554 :
555 : local_irq_enable();
556 :
557 754 : h = softirq_vec;
558 :
559 3770 : while ((softirq_bit = ffs(pending))) {
560 : unsigned int vec_nr;
561 : int prev_count;
562 :
563 754 : h += softirq_bit - 1;
564 :
565 754 : vec_nr = h - softirq_vec;
566 754 : prev_count = preempt_count();
567 :
568 754 : kstat_incr_softirqs_this_cpu(vec_nr);
569 :
570 754 : trace_softirq_entry(vec_nr);
571 754 : h->action(h);
572 754 : trace_softirq_exit(vec_nr);
573 754 : if (unlikely(prev_count != preempt_count())) {
574 0 : 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 : }
579 754 : h++;
580 754 : pending >>= softirq_bit;
581 : }
582 :
583 754 : if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
584 1508 : __this_cpu_read(ksoftirqd) == current)
585 : rcu_softirq_qs();
586 :
587 754 : local_irq_disable();
588 :
589 754 : pending = local_softirq_pending();
590 754 : if (pending) {
591 650 : if (time_before(jiffies, end) && !need_resched() &&
592 : --max_restart)
593 : goto restart;
594 :
595 : wakeup_softirqd();
596 : }
597 :
598 429 : account_softirq_exit(current);
599 429 : lockdep_softirq_end(in_hardirq);
600 429 : softirq_handle_end();
601 429 : current_restore_flags(old_flags, PF_MEMALLOC);
602 429 : }
603 :
604 : /**
605 : * irq_enter_rcu - Enter an interrupt context with RCU watching
606 : */
607 2723 : void irq_enter_rcu(void)
608 : {
609 2723 : __irq_enter_raw();
610 :
611 5446 : if (tick_nohz_full_cpu(smp_processor_id()) ||
612 5446 : (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)))
613 : tick_irq_enter();
614 :
615 2723 : account_hardirq_enter(current);
616 2723 : }
617 :
618 : /**
619 : * irq_enter - Enter an interrupt context including RCU update
620 : */
621 2723 : void irq_enter(void)
622 : {
623 : ct_irq_enter();
624 2723 : irq_enter_rcu();
625 2723 : }
626 :
627 : static 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 :
640 2723 : static 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 5446 : account_hardirq_exit(current);
648 2723 : preempt_count_sub(HARDIRQ_OFFSET);
649 2723 : if (!in_interrupt() && local_softirq_pending())
650 88 : invoke_softirq();
651 :
652 : tick_irq_exit();
653 2723 : }
654 :
655 : /**
656 : * irq_exit_rcu() - Exit an interrupt context without updating RCU
657 : *
658 : * Also processes softirqs if needed and possible.
659 : */
660 0 : void irq_exit_rcu(void)
661 : {
662 0 : __irq_exit_rcu();
663 : /* must be last! */
664 : lockdep_hardirq_exit();
665 0 : }
666 :
667 : /**
668 : * irq_exit - Exit an interrupt context, update RCU and lockdep
669 : *
670 : * Also processes softirqs if needed and possible.
671 : */
672 2723 : void irq_exit(void)
673 : {
674 2723 : __irq_exit_rcu();
675 : ct_irq_exit();
676 : /* must be last! */
677 : lockdep_hardirq_exit();
678 2723 : }
679 :
680 : /*
681 : * This function must run with irqs disabled!
682 : */
683 1078 : inline void raise_softirq_irqoff(unsigned int nr)
684 : {
685 1078 : __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 1078 : if (!in_interrupt() && should_wake_ksoftirqd())
697 : wakeup_softirqd();
698 1078 : }
699 :
700 87 : void raise_softirq(unsigned int nr)
701 : {
702 : unsigned long flags;
703 :
704 87 : local_irq_save(flags);
705 87 : raise_softirq_irqoff(nr);
706 174 : local_irq_restore(flags);
707 87 : }
708 :
709 0 : void __raise_softirq_irqoff(unsigned int nr)
710 : {
711 : lockdep_assert_irqs_disabled();
712 1078 : trace_softirq_raise(nr);
713 1078 : or_softirq_pending(1UL << nr);
714 0 : }
715 :
716 4 : void open_softirq(int nr, void (*action)(struct softirq_action *))
717 : {
718 6 : softirq_vec[nr].action = action;
719 4 : }
720 :
721 : /*
722 : * Tasklets
723 : */
724 : struct tasklet_head {
725 : struct tasklet_struct *head;
726 : struct tasklet_struct **tail;
727 : };
728 :
729 : static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
730 : static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
731 :
732 0 : static 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 0 : local_irq_save(flags);
740 0 : head = this_cpu_ptr(headp);
741 0 : t->next = NULL;
742 0 : *head->tail = t;
743 0 : head->tail = &(t->next);
744 0 : raise_softirq_irqoff(softirq_nr);
745 0 : local_irq_restore(flags);
746 0 : }
747 :
748 0 : void __tasklet_schedule(struct tasklet_struct *t)
749 : {
750 0 : __tasklet_schedule_common(t, &tasklet_vec,
751 : TASKLET_SOFTIRQ);
752 0 : }
753 : EXPORT_SYMBOL(__tasklet_schedule);
754 :
755 0 : void __tasklet_hi_schedule(struct tasklet_struct *t)
756 : {
757 0 : __tasklet_schedule_common(t, &tasklet_hi_vec,
758 : HI_SOFTIRQ);
759 0 : }
760 : EXPORT_SYMBOL(__tasklet_hi_schedule);
761 :
762 0 : static bool tasklet_clear_sched(struct tasklet_struct *t)
763 : {
764 0 : if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
765 0 : wake_up_var(&t->state);
766 0 : return true;
767 : }
768 :
769 0 : 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 :
776 0 : static 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 0 : list = tl_head->head;
784 0 : tl_head->head = NULL;
785 0 : tl_head->tail = &tl_head->head;
786 : local_irq_enable();
787 :
788 0 : while (list) {
789 0 : struct tasklet_struct *t = list;
790 :
791 0 : list = list->next;
792 :
793 0 : if (tasklet_trylock(t)) {
794 0 : if (!atomic_read(&t->count)) {
795 0 : if (tasklet_clear_sched(t)) {
796 0 : if (t->use_callback)
797 0 : t->callback(t);
798 : else
799 0 : t->func(t->data);
800 : }
801 0 : tasklet_unlock(t);
802 0 : continue;
803 : }
804 : tasklet_unlock(t);
805 : }
806 :
807 : local_irq_disable();
808 0 : t->next = NULL;
809 0 : *tl_head->tail = t;
810 0 : tl_head->tail = &t->next;
811 0 : __raise_softirq_irqoff(softirq_nr);
812 : local_irq_enable();
813 : }
814 0 : }
815 :
816 0 : static __latent_entropy void tasklet_action(struct softirq_action *a)
817 : {
818 0 : tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
819 0 : }
820 :
821 0 : static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
822 : {
823 0 : tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
824 0 : }
825 :
826 0 : void tasklet_setup(struct tasklet_struct *t,
827 : void (*callback)(struct tasklet_struct *))
828 : {
829 0 : t->next = NULL;
830 0 : t->state = 0;
831 0 : atomic_set(&t->count, 0);
832 0 : t->callback = callback;
833 0 : t->use_callback = true;
834 0 : t->data = 0;
835 0 : }
836 : EXPORT_SYMBOL(tasklet_setup);
837 :
838 0 : void tasklet_init(struct tasklet_struct *t,
839 : void (*func)(unsigned long), unsigned long data)
840 : {
841 0 : t->next = NULL;
842 0 : t->state = 0;
843 0 : atomic_set(&t->count, 0);
844 0 : t->func = func;
845 0 : t->use_callback = false;
846 0 : t->data = data;
847 0 : }
848 : EXPORT_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 : */
855 : void 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 : }
873 : EXPORT_SYMBOL(tasklet_unlock_spin_wait);
874 : #endif
875 :
876 0 : void tasklet_kill(struct tasklet_struct *t)
877 : {
878 0 : if (in_interrupt())
879 0 : pr_notice("Attempt to kill tasklet from interrupt\n");
880 :
881 0 : while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
882 0 : wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
883 :
884 0 : tasklet_unlock_wait(t);
885 0 : tasklet_clear_sched(t);
886 0 : }
887 : EXPORT_SYMBOL(tasklet_kill);
888 :
889 : #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
890 : void 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 : }
897 : EXPORT_SYMBOL_GPL(tasklet_unlock);
898 :
899 : void tasklet_unlock_wait(struct tasklet_struct *t)
900 : {
901 : wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
902 : }
903 : EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
904 : #endif
905 :
906 1 : void __init softirq_init(void)
907 : {
908 : int cpu;
909 :
910 2 : for_each_possible_cpu(cpu) {
911 2 : per_cpu(tasklet_vec, cpu).tail =
912 1 : &per_cpu(tasklet_vec, cpu).head;
913 2 : per_cpu(tasklet_hi_vec, cpu).tail =
914 1 : &per_cpu(tasklet_hi_vec, cpu).head;
915 : }
916 :
917 1 : open_softirq(TASKLET_SOFTIRQ, tasklet_action);
918 1 : open_softirq(HI_SOFTIRQ, tasklet_hi_action);
919 1 : }
920 :
921 685 : static int ksoftirqd_should_run(unsigned int cpu)
922 : {
923 685 : return local_softirq_pending();
924 : }
925 :
926 342 : static void run_ksoftirqd(unsigned int cpu)
927 : {
928 342 : ksoftirqd_run_begin();
929 342 : 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 : */
934 342 : __do_softirq();
935 : ksoftirqd_run_end();
936 342 : cond_resched();
937 342 : return;
938 : }
939 : ksoftirqd_run_end();
940 : }
941 :
942 : #ifdef CONFIG_HOTPLUG_CPU
943 : static 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 :
972 : static 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 :
979 1 : static __init int spawn_ksoftirqd(void)
980 : {
981 1 : cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
982 : takeover_tasklets);
983 1 : BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
984 :
985 1 : return 0;
986 : }
987 : early_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 :
994 0 : int __init __weak early_irq_init(void)
995 : {
996 0 : return 0;
997 : }
998 :
999 0 : int __init __weak arch_probe_nr_irqs(void)
1000 : {
1001 0 : return NR_IRQS_LEGACY;
1002 : }
1003 :
1004 1 : int __init __weak arch_early_irq_init(void)
1005 : {
1006 1 : return 0;
1007 : }
1008 :
1009 0 : unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
1010 : {
1011 0 : return from;
1012 : }
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