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1 | /* |
2 | * linux/kernel/softirq.c |
3 | * |
4 | * Copyright (C) 1992 Linus Torvalds |
5 | * |
6 | * Distribute under GPLv2. |
7 | * |
8 | * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) |
9 | * |
10 | * Remote softirq infrastructure is by Jens Axboe. |
11 | */ |
12 | |
13 | #include <linux/export.h> |
14 | #include <linux/kernel_stat.h> |
15 | #include <linux/interrupt.h> |
16 | #include <linux/init.h> |
17 | #include <linux/mm.h> |
18 | #include <linux/notifier.h> |
19 | #include <linux/percpu.h> |
20 | #include <linux/cpu.h> |
21 | #include <linux/freezer.h> |
22 | #include <linux/kthread.h> |
23 | #include <linux/rcupdate.h> |
24 | #include <linux/ftrace.h> |
25 | #include <linux/smp.h> |
26 | #include <linux/tick.h> |
27 | |
28 | #define CREATE_TRACE_POINTS |
29 | #include <trace/events/irq.h> |
30 | |
31 | #include <asm/irq.h> |
32 | /* |
33 | - No shared variables, all the data are CPU local. |
34 | - If a softirq needs serialization, let it serialize itself |
35 | by its own spinlocks. |
36 | - Even if softirq is serialized, only local cpu is marked for |
37 | execution. Hence, we get something sort of weak cpu binding. |
38 | Though it is still not clear, will it result in better locality |
39 | or will not. |
40 | |
41 | Examples: |
42 | - NET RX softirq. It is multithreaded and does not require |
43 | any global serialization. |
44 | - NET TX softirq. It kicks software netdevice queues, hence |
45 | it is logically serialized per device, but this serialization |
46 | is invisible to common code. |
47 | - Tasklets: serialized wrt itself. |
48 | */ |
49 | |
50 | #ifndef __ARCH_IRQ_STAT |
51 | irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned; |
52 | EXPORT_SYMBOL(irq_stat); |
53 | #endif |
54 | |
55 | static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
56 | |
57 | DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
58 | |
59 | char *softirq_to_name[NR_SOFTIRQS] = { |
60 | "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL", |
61 | "TASKLET", "SCHED", "HRTIMER", "RCU" |
62 | }; |
63 | |
64 | /* |
65 | * we cannot loop indefinitely here to avoid userspace starvation, |
66 | * but we also don't want to introduce a worst case 1/HZ latency |
67 | * to the pending events, so lets the scheduler to balance |
68 | * the softirq load for us. |
69 | */ |
70 | static void wakeup_softirqd(void) |
71 | { |
72 | /* Interrupts are disabled: no need to stop preemption */ |
73 | struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
74 | |
75 | if (tsk && tsk->state != TASK_RUNNING) |
76 | wake_up_process(tsk); |
77 | } |
78 | |
79 | /* |
80 | * preempt_count and SOFTIRQ_OFFSET usage: |
81 | * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving |
82 | * softirq processing. |
83 | * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) |
84 | * on local_bh_disable or local_bh_enable. |
85 | * This lets us distinguish between whether we are currently processing |
86 | * softirq and whether we just have bh disabled. |
87 | */ |
88 | |
89 | /* |
90 | * This one is for softirq.c-internal use, |
91 | * where hardirqs are disabled legitimately: |
92 | */ |
93 | #ifdef CONFIG_TRACE_IRQFLAGS |
94 | static void __local_bh_disable(unsigned long ip, unsigned int cnt) |
95 | { |
96 | unsigned long flags; |
97 | |
98 | WARN_ON_ONCE(in_irq()); |
99 | |
100 | raw_local_irq_save(flags); |
101 | /* |
102 | * The preempt tracer hooks into add_preempt_count and will break |
103 | * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET |
104 | * is set and before current->softirq_enabled is cleared. |
105 | * We must manually increment preempt_count here and manually |
106 | * call the trace_preempt_off later. |
107 | */ |
108 | preempt_count() += cnt; |
109 | /* |
110 | * Were softirqs turned off above: |
111 | */ |
112 | if (softirq_count() == cnt) |
113 | trace_softirqs_off(ip); |
114 | raw_local_irq_restore(flags); |
115 | |
116 | if (preempt_count() == cnt) |
117 | trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); |
118 | } |
119 | #else /* !CONFIG_TRACE_IRQFLAGS */ |
120 | static inline void __local_bh_disable(unsigned long ip, unsigned int cnt) |
121 | { |
122 | add_preempt_count(cnt); |
123 | barrier(); |
124 | } |
125 | #endif /* CONFIG_TRACE_IRQFLAGS */ |
126 | |
127 | void local_bh_disable(void) |
128 | { |
129 | __local_bh_disable((unsigned long)__builtin_return_address(0), |
130 | SOFTIRQ_DISABLE_OFFSET); |
131 | } |
132 | |
133 | EXPORT_SYMBOL(local_bh_disable); |
134 | |
135 | static void __local_bh_enable(unsigned int cnt) |
136 | { |
137 | WARN_ON_ONCE(in_irq()); |
138 | WARN_ON_ONCE(!irqs_disabled()); |
139 | |
140 | if (softirq_count() == cnt) |
141 | trace_softirqs_on((unsigned long)__builtin_return_address(0)); |
142 | sub_preempt_count(cnt); |
143 | } |
144 | |
145 | /* |
146 | * Special-case - softirqs can safely be enabled in |
147 | * cond_resched_softirq(), or by __do_softirq(), |
148 | * without processing still-pending softirqs: |
149 | */ |
150 | void _local_bh_enable(void) |
151 | { |
152 | __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); |
153 | } |
154 | |
155 | EXPORT_SYMBOL(_local_bh_enable); |
156 | |
157 | static inline void _local_bh_enable_ip(unsigned long ip) |
158 | { |
159 | WARN_ON_ONCE(in_irq() || irqs_disabled()); |
160 | #ifdef CONFIG_TRACE_IRQFLAGS |
161 | local_irq_disable(); |
162 | #endif |
163 | /* |
164 | * Are softirqs going to be turned on now: |
165 | */ |
166 | if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) |
167 | trace_softirqs_on(ip); |
168 | /* |
169 | * Keep preemption disabled until we are done with |
170 | * softirq processing: |
171 | */ |
172 | sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1); |
173 | |
174 | if (unlikely(!in_interrupt() && local_softirq_pending())) |
175 | do_softirq(); |
176 | |
177 | dec_preempt_count(); |
178 | #ifdef CONFIG_TRACE_IRQFLAGS |
179 | local_irq_enable(); |
180 | #endif |
181 | preempt_check_resched(); |
182 | } |
183 | |
184 | void local_bh_enable(void) |
185 | { |
186 | _local_bh_enable_ip((unsigned long)__builtin_return_address(0)); |
187 | } |
188 | EXPORT_SYMBOL(local_bh_enable); |
189 | |
190 | void local_bh_enable_ip(unsigned long ip) |
191 | { |
192 | _local_bh_enable_ip(ip); |
193 | } |
194 | EXPORT_SYMBOL(local_bh_enable_ip); |
195 | |
196 | /* |
197 | * We restart softirq processing MAX_SOFTIRQ_RESTART times, |
198 | * and we fall back to softirqd after that. |
199 | * |
200 | * This number has been established via experimentation. |
201 | * The two things to balance is latency against fairness - |
202 | * we want to handle softirqs as soon as possible, but they |
203 | * should not be able to lock up the box. |
204 | */ |
205 | #define MAX_SOFTIRQ_RESTART 10 |
206 | |
207 | asmlinkage void __do_softirq(void) |
208 | { |
209 | struct softirq_action *h; |
210 | __u32 pending; |
211 | int max_restart = MAX_SOFTIRQ_RESTART; |
212 | int cpu; |
213 | |
214 | pending = local_softirq_pending(); |
215 | account_system_vtime(current); |
216 | |
217 | __local_bh_disable((unsigned long)__builtin_return_address(0), |
218 | SOFTIRQ_OFFSET); |
219 | lockdep_softirq_enter(); |
220 | |
221 | cpu = smp_processor_id(); |
222 | restart: |
223 | /* Reset the pending bitmask before enabling irqs */ |
224 | set_softirq_pending(0); |
225 | |
226 | local_irq_enable(); |
227 | |
228 | h = softirq_vec; |
229 | |
230 | do { |
231 | if (pending & 1) { |
232 | unsigned int vec_nr = h - softirq_vec; |
233 | int prev_count = preempt_count(); |
234 | |
235 | kstat_incr_softirqs_this_cpu(vec_nr); |
236 | |
237 | trace_softirq_entry(vec_nr); |
238 | h->action(h); |
239 | trace_softirq_exit(vec_nr); |
240 | if (unlikely(prev_count != preempt_count())) { |
241 | printk(KERN_ERR "huh, entered softirq %u %s %p" |
242 | "with preempt_count %08x," |
243 | " exited with %08x?\n", vec_nr, |
244 | softirq_to_name[vec_nr], h->action, |
245 | prev_count, preempt_count()); |
246 | preempt_count() = prev_count; |
247 | } |
248 | |
249 | rcu_bh_qs(cpu); |
250 | } |
251 | h++; |
252 | pending >>= 1; |
253 | } while (pending); |
254 | |
255 | local_irq_disable(); |
256 | |
257 | pending = local_softirq_pending(); |
258 | if (pending && --max_restart) |
259 | goto restart; |
260 | |
261 | if (pending) |
262 | wakeup_softirqd(); |
263 | |
264 | lockdep_softirq_exit(); |
265 | |
266 | account_system_vtime(current); |
267 | __local_bh_enable(SOFTIRQ_OFFSET); |
268 | } |
269 | |
270 | #ifndef __ARCH_HAS_DO_SOFTIRQ |
271 | |
272 | asmlinkage void do_softirq(void) |
273 | { |
274 | __u32 pending; |
275 | unsigned long flags; |
276 | |
277 | if (in_interrupt()) |
278 | return; |
279 | |
280 | local_irq_save(flags); |
281 | |
282 | pending = local_softirq_pending(); |
283 | |
284 | if (pending) |
285 | __do_softirq(); |
286 | |
287 | local_irq_restore(flags); |
288 | } |
289 | |
290 | #endif |
291 | |
292 | /* |
293 | * Enter an interrupt context. |
294 | */ |
295 | void irq_enter(void) |
296 | { |
297 | int cpu = smp_processor_id(); |
298 | |
299 | rcu_irq_enter(); |
300 | if (idle_cpu(cpu) && !in_interrupt()) { |
301 | /* |
302 | * Prevent raise_softirq from needlessly waking up ksoftirqd |
303 | * here, as softirq will be serviced on return from interrupt. |
304 | */ |
305 | local_bh_disable(); |
306 | tick_check_idle(cpu); |
307 | _local_bh_enable(); |
308 | } |
309 | |
310 | __irq_enter(); |
311 | } |
312 | |
313 | #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED |
314 | static inline void invoke_softirq(void) |
315 | { |
316 | if (!force_irqthreads) |
317 | __do_softirq(); |
318 | else { |
319 | __local_bh_disable((unsigned long)__builtin_return_address(0), |
320 | SOFTIRQ_OFFSET); |
321 | wakeup_softirqd(); |
322 | __local_bh_enable(SOFTIRQ_OFFSET); |
323 | } |
324 | } |
325 | #else |
326 | static inline void invoke_softirq(void) |
327 | { |
328 | if (!force_irqthreads) |
329 | do_softirq(); |
330 | else { |
331 | __local_bh_disable((unsigned long)__builtin_return_address(0), |
332 | SOFTIRQ_OFFSET); |
333 | wakeup_softirqd(); |
334 | __local_bh_enable(SOFTIRQ_OFFSET); |
335 | } |
336 | } |
337 | #endif |
338 | |
339 | /* |
340 | * Exit an interrupt context. Process softirqs if needed and possible: |
341 | */ |
342 | void irq_exit(void) |
343 | { |
344 | account_system_vtime(current); |
345 | trace_hardirq_exit(); |
346 | sub_preempt_count(IRQ_EXIT_OFFSET); |
347 | if (!in_interrupt() && local_softirq_pending()) |
348 | invoke_softirq(); |
349 | |
350 | rcu_irq_exit(); |
351 | #ifdef CONFIG_NO_HZ |
352 | /* Make sure that timer wheel updates are propagated */ |
353 | if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched()) |
354 | tick_nohz_stop_sched_tick(0); |
355 | #endif |
356 | preempt_enable_no_resched(); |
357 | } |
358 | |
359 | /* |
360 | * This function must run with irqs disabled! |
361 | */ |
362 | inline void raise_softirq_irqoff(unsigned int nr) |
363 | { |
364 | __raise_softirq_irqoff(nr); |
365 | |
366 | /* |
367 | * If we're in an interrupt or softirq, we're done |
368 | * (this also catches softirq-disabled code). We will |
369 | * actually run the softirq once we return from |
370 | * the irq or softirq. |
371 | * |
372 | * Otherwise we wake up ksoftirqd to make sure we |
373 | * schedule the softirq soon. |
374 | */ |
375 | if (!in_interrupt()) |
376 | wakeup_softirqd(); |
377 | } |
378 | |
379 | void raise_softirq(unsigned int nr) |
380 | { |
381 | unsigned long flags; |
382 | |
383 | local_irq_save(flags); |
384 | raise_softirq_irqoff(nr); |
385 | local_irq_restore(flags); |
386 | } |
387 | |
388 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
389 | { |
390 | softirq_vec[nr].action = action; |
391 | } |
392 | |
393 | /* |
394 | * Tasklets |
395 | */ |
396 | struct tasklet_head |
397 | { |
398 | struct tasklet_struct *head; |
399 | struct tasklet_struct **tail; |
400 | }; |
401 | |
402 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
403 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); |
404 | |
405 | void __tasklet_schedule(struct tasklet_struct *t) |
406 | { |
407 | unsigned long flags; |
408 | |
409 | local_irq_save(flags); |
410 | t->next = NULL; |
411 | *__this_cpu_read(tasklet_vec.tail) = t; |
412 | __this_cpu_write(tasklet_vec.tail, &(t->next)); |
413 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
414 | local_irq_restore(flags); |
415 | } |
416 | |
417 | EXPORT_SYMBOL(__tasklet_schedule); |
418 | |
419 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
420 | { |
421 | unsigned long flags; |
422 | |
423 | local_irq_save(flags); |
424 | t->next = NULL; |
425 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
426 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); |
427 | raise_softirq_irqoff(HI_SOFTIRQ); |
428 | local_irq_restore(flags); |
429 | } |
430 | |
431 | EXPORT_SYMBOL(__tasklet_hi_schedule); |
432 | |
433 | void __tasklet_hi_schedule_first(struct tasklet_struct *t) |
434 | { |
435 | BUG_ON(!irqs_disabled()); |
436 | |
437 | t->next = __this_cpu_read(tasklet_hi_vec.head); |
438 | __this_cpu_write(tasklet_hi_vec.head, t); |
439 | __raise_softirq_irqoff(HI_SOFTIRQ); |
440 | } |
441 | |
442 | EXPORT_SYMBOL(__tasklet_hi_schedule_first); |
443 | |
444 | static void tasklet_action(struct softirq_action *a) |
445 | { |
446 | struct tasklet_struct *list; |
447 | |
448 | local_irq_disable(); |
449 | list = __this_cpu_read(tasklet_vec.head); |
450 | __this_cpu_write(tasklet_vec.head, NULL); |
451 | __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head); |
452 | local_irq_enable(); |
453 | |
454 | while (list) { |
455 | struct tasklet_struct *t = list; |
456 | |
457 | list = list->next; |
458 | |
459 | if (tasklet_trylock(t)) { |
460 | if (!atomic_read(&t->count)) { |
461 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
462 | BUG(); |
463 | t->func(t->data); |
464 | tasklet_unlock(t); |
465 | continue; |
466 | } |
467 | tasklet_unlock(t); |
468 | } |
469 | |
470 | local_irq_disable(); |
471 | t->next = NULL; |
472 | *__this_cpu_read(tasklet_vec.tail) = t; |
473 | __this_cpu_write(tasklet_vec.tail, &(t->next)); |
474 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
475 | local_irq_enable(); |
476 | } |
477 | } |
478 | |
479 | static void tasklet_hi_action(struct softirq_action *a) |
480 | { |
481 | struct tasklet_struct *list; |
482 | |
483 | local_irq_disable(); |
484 | list = __this_cpu_read(tasklet_hi_vec.head); |
485 | __this_cpu_write(tasklet_hi_vec.head, NULL); |
486 | __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head); |
487 | local_irq_enable(); |
488 | |
489 | while (list) { |
490 | struct tasklet_struct *t = list; |
491 | |
492 | list = list->next; |
493 | |
494 | if (tasklet_trylock(t)) { |
495 | if (!atomic_read(&t->count)) { |
496 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
497 | BUG(); |
498 | t->func(t->data); |
499 | tasklet_unlock(t); |
500 | continue; |
501 | } |
502 | tasklet_unlock(t); |
503 | } |
504 | |
505 | local_irq_disable(); |
506 | t->next = NULL; |
507 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
508 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); |
509 | __raise_softirq_irqoff(HI_SOFTIRQ); |
510 | local_irq_enable(); |
511 | } |
512 | } |
513 | |
514 | |
515 | void tasklet_init(struct tasklet_struct *t, |
516 | void (*func)(unsigned long), unsigned long data) |
517 | { |
518 | t->next = NULL; |
519 | t->state = 0; |
520 | atomic_set(&t->count, 0); |
521 | t->func = func; |
522 | t->data = data; |
523 | } |
524 | |
525 | EXPORT_SYMBOL(tasklet_init); |
526 | |
527 | void tasklet_kill(struct tasklet_struct *t) |
528 | { |
529 | if (in_interrupt()) |
530 | printk("Attempt to kill tasklet from interrupt\n"); |
531 | |
532 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { |
533 | do { |
534 | yield(); |
535 | } while (test_bit(TASKLET_STATE_SCHED, &t->state)); |
536 | } |
537 | tasklet_unlock_wait(t); |
538 | clear_bit(TASKLET_STATE_SCHED, &t->state); |
539 | } |
540 | |
541 | EXPORT_SYMBOL(tasklet_kill); |
542 | |
543 | /* |
544 | * tasklet_hrtimer |
545 | */ |
546 | |
547 | /* |
548 | * The trampoline is called when the hrtimer expires. It schedules a tasklet |
549 | * to run __tasklet_hrtimer_trampoline() which in turn will call the intended |
550 | * hrtimer callback, but from softirq context. |
551 | */ |
552 | static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer) |
553 | { |
554 | struct tasklet_hrtimer *ttimer = |
555 | container_of(timer, struct tasklet_hrtimer, timer); |
556 | |
557 | tasklet_hi_schedule(&ttimer->tasklet); |
558 | return HRTIMER_NORESTART; |
559 | } |
560 | |
561 | /* |
562 | * Helper function which calls the hrtimer callback from |
563 | * tasklet/softirq context |
564 | */ |
565 | static void __tasklet_hrtimer_trampoline(unsigned long data) |
566 | { |
567 | struct tasklet_hrtimer *ttimer = (void *)data; |
568 | enum hrtimer_restart restart; |
569 | |
570 | restart = ttimer->function(&ttimer->timer); |
571 | if (restart != HRTIMER_NORESTART) |
572 | hrtimer_restart(&ttimer->timer); |
573 | } |
574 | |
575 | /** |
576 | * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks |
577 | * @ttimer: tasklet_hrtimer which is initialized |
578 | * @function: hrtimer callback function which gets called from softirq context |
579 | * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME) |
580 | * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL) |
581 | */ |
582 | void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer, |
583 | enum hrtimer_restart (*function)(struct hrtimer *), |
584 | clockid_t which_clock, enum hrtimer_mode mode) |
585 | { |
586 | hrtimer_init(&ttimer->timer, which_clock, mode); |
587 | ttimer->timer.function = __hrtimer_tasklet_trampoline; |
588 | tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline, |
589 | (unsigned long)ttimer); |
590 | ttimer->function = function; |
591 | } |
592 | EXPORT_SYMBOL_GPL(tasklet_hrtimer_init); |
593 | |
594 | /* |
595 | * Remote softirq bits |
596 | */ |
597 | |
598 | DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); |
599 | EXPORT_PER_CPU_SYMBOL(softirq_work_list); |
600 | |
601 | static void __local_trigger(struct call_single_data *cp, int softirq) |
602 | { |
603 | struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]); |
604 | |
605 | list_add_tail(&cp->list, head); |
606 | |
607 | /* Trigger the softirq only if the list was previously empty. */ |
608 | if (head->next == &cp->list) |
609 | raise_softirq_irqoff(softirq); |
610 | } |
611 | |
612 | #ifdef CONFIG_USE_GENERIC_SMP_HELPERS |
613 | static void remote_softirq_receive(void *data) |
614 | { |
615 | struct call_single_data *cp = data; |
616 | unsigned long flags; |
617 | int softirq; |
618 | |
619 | softirq = cp->priv; |
620 | |
621 | local_irq_save(flags); |
622 | __local_trigger(cp, softirq); |
623 | local_irq_restore(flags); |
624 | } |
625 | |
626 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) |
627 | { |
628 | if (cpu_online(cpu)) { |
629 | cp->func = remote_softirq_receive; |
630 | cp->info = cp; |
631 | cp->flags = 0; |
632 | cp->priv = softirq; |
633 | |
634 | __smp_call_function_single(cpu, cp, 0); |
635 | return 0; |
636 | } |
637 | return 1; |
638 | } |
639 | #else /* CONFIG_USE_GENERIC_SMP_HELPERS */ |
640 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) |
641 | { |
642 | return 1; |
643 | } |
644 | #endif |
645 | |
646 | /** |
647 | * __send_remote_softirq - try to schedule softirq work on a remote cpu |
648 | * @cp: private SMP call function data area |
649 | * @cpu: the remote cpu |
650 | * @this_cpu: the currently executing cpu |
651 | * @softirq: the softirq for the work |
652 | * |
653 | * Attempt to schedule softirq work on a remote cpu. If this cannot be |
654 | * done, the work is instead queued up on the local cpu. |
655 | * |
656 | * Interrupts must be disabled. |
657 | */ |
658 | void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq) |
659 | { |
660 | if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq)) |
661 | __local_trigger(cp, softirq); |
662 | } |
663 | EXPORT_SYMBOL(__send_remote_softirq); |
664 | |
665 | /** |
666 | * send_remote_softirq - try to schedule softirq work on a remote cpu |
667 | * @cp: private SMP call function data area |
668 | * @cpu: the remote cpu |
669 | * @softirq: the softirq for the work |
670 | * |
671 | * Like __send_remote_softirq except that disabling interrupts and |
672 | * computing the current cpu is done for the caller. |
673 | */ |
674 | void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq) |
675 | { |
676 | unsigned long flags; |
677 | int this_cpu; |
678 | |
679 | local_irq_save(flags); |
680 | this_cpu = smp_processor_id(); |
681 | __send_remote_softirq(cp, cpu, this_cpu, softirq); |
682 | local_irq_restore(flags); |
683 | } |
684 | EXPORT_SYMBOL(send_remote_softirq); |
685 | |
686 | static int __cpuinit remote_softirq_cpu_notify(struct notifier_block *self, |
687 | unsigned long action, void *hcpu) |
688 | { |
689 | /* |
690 | * If a CPU goes away, splice its entries to the current CPU |
691 | * and trigger a run of the softirq |
692 | */ |
693 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { |
694 | int cpu = (unsigned long) hcpu; |
695 | int i; |
696 | |
697 | local_irq_disable(); |
698 | for (i = 0; i < NR_SOFTIRQS; i++) { |
699 | struct list_head *head = &per_cpu(softirq_work_list[i], cpu); |
700 | struct list_head *local_head; |
701 | |
702 | if (list_empty(head)) |
703 | continue; |
704 | |
705 | local_head = &__get_cpu_var(softirq_work_list[i]); |
706 | list_splice_init(head, local_head); |
707 | raise_softirq_irqoff(i); |
708 | } |
709 | local_irq_enable(); |
710 | } |
711 | |
712 | return NOTIFY_OK; |
713 | } |
714 | |
715 | static struct notifier_block __cpuinitdata remote_softirq_cpu_notifier = { |
716 | .notifier_call = remote_softirq_cpu_notify, |
717 | }; |
718 | |
719 | void __init softirq_init(void) |
720 | { |
721 | int cpu; |
722 | |
723 | for_each_possible_cpu(cpu) { |
724 | int i; |
725 | |
726 | per_cpu(tasklet_vec, cpu).tail = |
727 | &per_cpu(tasklet_vec, cpu).head; |
728 | per_cpu(tasklet_hi_vec, cpu).tail = |
729 | &per_cpu(tasklet_hi_vec, cpu).head; |
730 | for (i = 0; i < NR_SOFTIRQS; i++) |
731 | INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu)); |
732 | } |
733 | |
734 | register_hotcpu_notifier(&remote_softirq_cpu_notifier); |
735 | |
736 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
737 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); |
738 | } |
739 | |
740 | static int run_ksoftirqd(void * __bind_cpu) |
741 | { |
742 | set_current_state(TASK_INTERRUPTIBLE); |
743 | |
744 | while (!kthread_should_stop()) { |
745 | preempt_disable(); |
746 | if (!local_softirq_pending()) { |
747 | preempt_enable_no_resched(); |
748 | schedule(); |
749 | preempt_disable(); |
750 | } |
751 | |
752 | __set_current_state(TASK_RUNNING); |
753 | |
754 | while (local_softirq_pending()) { |
755 | /* Preempt disable stops cpu going offline. |
756 | If already offline, we'll be on wrong CPU: |
757 | don't process */ |
758 | if (cpu_is_offline((long)__bind_cpu)) |
759 | goto wait_to_die; |
760 | local_irq_disable(); |
761 | if (local_softirq_pending()) |
762 | __do_softirq(); |
763 | local_irq_enable(); |
764 | preempt_enable_no_resched(); |
765 | cond_resched(); |
766 | preempt_disable(); |
767 | rcu_note_context_switch((long)__bind_cpu); |
768 | } |
769 | preempt_enable(); |
770 | set_current_state(TASK_INTERRUPTIBLE); |
771 | } |
772 | __set_current_state(TASK_RUNNING); |
773 | return 0; |
774 | |
775 | wait_to_die: |
776 | preempt_enable(); |
777 | /* Wait for kthread_stop */ |
778 | set_current_state(TASK_INTERRUPTIBLE); |
779 | while (!kthread_should_stop()) { |
780 | schedule(); |
781 | set_current_state(TASK_INTERRUPTIBLE); |
782 | } |
783 | __set_current_state(TASK_RUNNING); |
784 | return 0; |
785 | } |
786 | |
787 | #ifdef CONFIG_HOTPLUG_CPU |
788 | /* |
789 | * tasklet_kill_immediate is called to remove a tasklet which can already be |
790 | * scheduled for execution on @cpu. |
791 | * |
792 | * Unlike tasklet_kill, this function removes the tasklet |
793 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. |
794 | * |
795 | * When this function is called, @cpu must be in the CPU_DEAD state. |
796 | */ |
797 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) |
798 | { |
799 | struct tasklet_struct **i; |
800 | |
801 | BUG_ON(cpu_online(cpu)); |
802 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); |
803 | |
804 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) |
805 | return; |
806 | |
807 | /* CPU is dead, so no lock needed. */ |
808 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
809 | if (*i == t) { |
810 | *i = t->next; |
811 | /* If this was the tail element, move the tail ptr */ |
812 | if (*i == NULL) |
813 | per_cpu(tasklet_vec, cpu).tail = i; |
814 | return; |
815 | } |
816 | } |
817 | BUG(); |
818 | } |
819 | |
820 | static void takeover_tasklets(unsigned int cpu) |
821 | { |
822 | /* CPU is dead, so no lock needed. */ |
823 | local_irq_disable(); |
824 | |
825 | /* Find end, append list for that CPU. */ |
826 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
827 | *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; |
828 | this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); |
829 | per_cpu(tasklet_vec, cpu).head = NULL; |
830 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; |
831 | } |
832 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
833 | |
834 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
835 | *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; |
836 | __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); |
837 | per_cpu(tasklet_hi_vec, cpu).head = NULL; |
838 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; |
839 | } |
840 | raise_softirq_irqoff(HI_SOFTIRQ); |
841 | |
842 | local_irq_enable(); |
843 | } |
844 | #endif /* CONFIG_HOTPLUG_CPU */ |
845 | |
846 | static int __cpuinit cpu_callback(struct notifier_block *nfb, |
847 | unsigned long action, |
848 | void *hcpu) |
849 | { |
850 | int hotcpu = (unsigned long)hcpu; |
851 | struct task_struct *p; |
852 | |
853 | switch (action) { |
854 | case CPU_UP_PREPARE: |
855 | case CPU_UP_PREPARE_FROZEN: |
856 | p = kthread_create_on_node(run_ksoftirqd, |
857 | hcpu, |
858 | cpu_to_node(hotcpu), |
859 | "ksoftirqd/%d", hotcpu); |
860 | if (IS_ERR(p)) { |
861 | printk("ksoftirqd for %i failed\n", hotcpu); |
862 | return notifier_from_errno(PTR_ERR(p)); |
863 | } |
864 | kthread_bind(p, hotcpu); |
865 | per_cpu(ksoftirqd, hotcpu) = p; |
866 | break; |
867 | case CPU_ONLINE: |
868 | case CPU_ONLINE_FROZEN: |
869 | wake_up_process(per_cpu(ksoftirqd, hotcpu)); |
870 | break; |
871 | #ifdef CONFIG_HOTPLUG_CPU |
872 | case CPU_UP_CANCELED: |
873 | case CPU_UP_CANCELED_FROZEN: |
874 | if (!per_cpu(ksoftirqd, hotcpu)) |
875 | break; |
876 | /* Unbind so it can run. Fall thru. */ |
877 | kthread_bind(per_cpu(ksoftirqd, hotcpu), |
878 | cpumask_any(cpu_online_mask)); |
879 | case CPU_DEAD: |
880 | case CPU_DEAD_FROZEN: { |
881 | static const struct sched_param param = { |
882 | .sched_priority = MAX_RT_PRIO-1 |
883 | }; |
884 | |
885 | p = per_cpu(ksoftirqd, hotcpu); |
886 | per_cpu(ksoftirqd, hotcpu) = NULL; |
887 | sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); |
888 | kthread_stop(p); |
889 | takeover_tasklets(hotcpu); |
890 | break; |
891 | } |
892 | #endif /* CONFIG_HOTPLUG_CPU */ |
893 | } |
894 | return NOTIFY_OK; |
895 | } |
896 | |
897 | static struct notifier_block __cpuinitdata cpu_nfb = { |
898 | .notifier_call = cpu_callback |
899 | }; |
900 | |
901 | static __init int spawn_ksoftirqd(void) |
902 | { |
903 | void *cpu = (void *)(long)smp_processor_id(); |
904 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
905 | |
906 | BUG_ON(err != NOTIFY_OK); |
907 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
908 | register_cpu_notifier(&cpu_nfb); |
909 | return 0; |
910 | } |
911 | early_initcall(spawn_ksoftirqd); |
912 | |
913 | /* |
914 | * [ These __weak aliases are kept in a separate compilation unit, so that |
915 | * GCC does not inline them incorrectly. ] |
916 | */ |
917 | |
918 | int __init __weak early_irq_init(void) |
919 | { |
920 | return 0; |
921 | } |
922 | |
923 | #ifdef CONFIG_GENERIC_HARDIRQS |
924 | int __init __weak arch_probe_nr_irqs(void) |
925 | { |
926 | return NR_IRQS_LEGACY; |
927 | } |
928 | |
929 | int __init __weak arch_early_irq_init(void) |
930 | { |
931 | return 0; |
932 | } |
933 | #endif |
934 |
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