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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/module.h> |
14 | #include <linux/kernel_stat.h> |
15 | #include <linux/interrupt.h> |
16 | #include <linux/init.h> |
17 | #include <linux/mm.h> |
18 | #include <linux/notifier.h> |
19 | #include <linux/percpu.h> |
20 | #include <linux/cpu.h> |
21 | #include <linux/freezer.h> |
22 | #include <linux/kthread.h> |
23 | #include <linux/rcupdate.h> |
24 | #include <linux/ftrace.h> |
25 | #include <linux/smp.h> |
26 | #include <linux/tick.h> |
27 | |
28 | #define CREATE_TRACE_POINTS |
29 | #include <trace/events/irq.h> |
30 | |
31 | #include <asm/irq.h> |
32 | /* |
33 | - No shared variables, all the data are CPU local. |
34 | - If a softirq needs serialization, let it serialize itself |
35 | by its own spinlocks. |
36 | - Even if softirq is serialized, only local cpu is marked for |
37 | execution. Hence, we get something sort of weak cpu binding. |
38 | Though it is still not clear, will it result in better locality |
39 | or will not. |
40 | |
41 | Examples: |
42 | - NET RX softirq. It is multithreaded and does not require |
43 | any global serialization. |
44 | - NET TX softirq. It kicks software netdevice queues, hence |
45 | it is logically serialized per device, but this serialization |
46 | is invisible to common code. |
47 | - Tasklets: serialized wrt itself. |
48 | */ |
49 | |
50 | #ifndef __ARCH_IRQ_STAT |
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 | static 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 = __get_cpu_var(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 | # define invoke_softirq() __do_softirq() |
315 | #else |
316 | # define invoke_softirq() do_softirq() |
317 | #endif |
318 | |
319 | /* |
320 | * Exit an interrupt context. Process softirqs if needed and possible: |
321 | */ |
322 | void irq_exit(void) |
323 | { |
324 | account_system_vtime(current); |
325 | trace_hardirq_exit(); |
326 | sub_preempt_count(IRQ_EXIT_OFFSET); |
327 | if (!in_interrupt() && local_softirq_pending()) |
328 | invoke_softirq(); |
329 | |
330 | rcu_irq_exit(); |
331 | #ifdef CONFIG_NO_HZ |
332 | /* Make sure that timer wheel updates are propagated */ |
333 | if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched()) |
334 | tick_nohz_stop_sched_tick(0); |
335 | #endif |
336 | preempt_enable_no_resched(); |
337 | } |
338 | |
339 | /* |
340 | * This function must run with irqs disabled! |
341 | */ |
342 | inline void raise_softirq_irqoff(unsigned int nr) |
343 | { |
344 | __raise_softirq_irqoff(nr); |
345 | |
346 | /* |
347 | * If we're in an interrupt or softirq, we're done |
348 | * (this also catches softirq-disabled code). We will |
349 | * actually run the softirq once we return from |
350 | * the irq or softirq. |
351 | * |
352 | * Otherwise we wake up ksoftirqd to make sure we |
353 | * schedule the softirq soon. |
354 | */ |
355 | if (!in_interrupt()) |
356 | wakeup_softirqd(); |
357 | } |
358 | |
359 | void raise_softirq(unsigned int nr) |
360 | { |
361 | unsigned long flags; |
362 | |
363 | local_irq_save(flags); |
364 | raise_softirq_irqoff(nr); |
365 | local_irq_restore(flags); |
366 | } |
367 | |
368 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
369 | { |
370 | softirq_vec[nr].action = action; |
371 | } |
372 | |
373 | /* |
374 | * Tasklets |
375 | */ |
376 | struct tasklet_head |
377 | { |
378 | struct tasklet_struct *head; |
379 | struct tasklet_struct **tail; |
380 | }; |
381 | |
382 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
383 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); |
384 | |
385 | void __tasklet_schedule(struct tasklet_struct *t) |
386 | { |
387 | unsigned long flags; |
388 | |
389 | local_irq_save(flags); |
390 | t->next = NULL; |
391 | *__get_cpu_var(tasklet_vec).tail = t; |
392 | __get_cpu_var(tasklet_vec).tail = &(t->next); |
393 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
394 | local_irq_restore(flags); |
395 | } |
396 | |
397 | EXPORT_SYMBOL(__tasklet_schedule); |
398 | |
399 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
400 | { |
401 | unsigned long flags; |
402 | |
403 | local_irq_save(flags); |
404 | t->next = NULL; |
405 | *__get_cpu_var(tasklet_hi_vec).tail = t; |
406 | __get_cpu_var(tasklet_hi_vec).tail = &(t->next); |
407 | raise_softirq_irqoff(HI_SOFTIRQ); |
408 | local_irq_restore(flags); |
409 | } |
410 | |
411 | EXPORT_SYMBOL(__tasklet_hi_schedule); |
412 | |
413 | void __tasklet_hi_schedule_first(struct tasklet_struct *t) |
414 | { |
415 | BUG_ON(!irqs_disabled()); |
416 | |
417 | t->next = __get_cpu_var(tasklet_hi_vec).head; |
418 | __get_cpu_var(tasklet_hi_vec).head = t; |
419 | __raise_softirq_irqoff(HI_SOFTIRQ); |
420 | } |
421 | |
422 | EXPORT_SYMBOL(__tasklet_hi_schedule_first); |
423 | |
424 | static void tasklet_action(struct softirq_action *a) |
425 | { |
426 | struct tasklet_struct *list; |
427 | |
428 | local_irq_disable(); |
429 | list = __get_cpu_var(tasklet_vec).head; |
430 | __get_cpu_var(tasklet_vec).head = NULL; |
431 | __get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head; |
432 | local_irq_enable(); |
433 | |
434 | while (list) { |
435 | struct tasklet_struct *t = list; |
436 | |
437 | list = list->next; |
438 | |
439 | if (tasklet_trylock(t)) { |
440 | if (!atomic_read(&t->count)) { |
441 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
442 | BUG(); |
443 | t->func(t->data); |
444 | tasklet_unlock(t); |
445 | continue; |
446 | } |
447 | tasklet_unlock(t); |
448 | } |
449 | |
450 | local_irq_disable(); |
451 | t->next = NULL; |
452 | *__get_cpu_var(tasklet_vec).tail = t; |
453 | __get_cpu_var(tasklet_vec).tail = &(t->next); |
454 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
455 | local_irq_enable(); |
456 | } |
457 | } |
458 | |
459 | static void tasklet_hi_action(struct softirq_action *a) |
460 | { |
461 | struct tasklet_struct *list; |
462 | |
463 | local_irq_disable(); |
464 | list = __get_cpu_var(tasklet_hi_vec).head; |
465 | __get_cpu_var(tasklet_hi_vec).head = NULL; |
466 | __get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head; |
467 | local_irq_enable(); |
468 | |
469 | while (list) { |
470 | struct tasklet_struct *t = list; |
471 | |
472 | list = list->next; |
473 | |
474 | if (tasklet_trylock(t)) { |
475 | if (!atomic_read(&t->count)) { |
476 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
477 | BUG(); |
478 | t->func(t->data); |
479 | tasklet_unlock(t); |
480 | continue; |
481 | } |
482 | tasklet_unlock(t); |
483 | } |
484 | |
485 | local_irq_disable(); |
486 | t->next = NULL; |
487 | *__get_cpu_var(tasklet_hi_vec).tail = t; |
488 | __get_cpu_var(tasklet_hi_vec).tail = &(t->next); |
489 | __raise_softirq_irqoff(HI_SOFTIRQ); |
490 | local_irq_enable(); |
491 | } |
492 | } |
493 | |
494 | |
495 | void tasklet_init(struct tasklet_struct *t, |
496 | void (*func)(unsigned long), unsigned long data) |
497 | { |
498 | t->next = NULL; |
499 | t->state = 0; |
500 | atomic_set(&t->count, 0); |
501 | t->func = func; |
502 | t->data = data; |
503 | } |
504 | |
505 | EXPORT_SYMBOL(tasklet_init); |
506 | |
507 | void tasklet_kill(struct tasklet_struct *t) |
508 | { |
509 | if (in_interrupt()) |
510 | printk("Attempt to kill tasklet from interrupt\n"); |
511 | |
512 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { |
513 | do { |
514 | yield(); |
515 | } while (test_bit(TASKLET_STATE_SCHED, &t->state)); |
516 | } |
517 | tasklet_unlock_wait(t); |
518 | clear_bit(TASKLET_STATE_SCHED, &t->state); |
519 | } |
520 | |
521 | EXPORT_SYMBOL(tasklet_kill); |
522 | |
523 | /* |
524 | * tasklet_hrtimer |
525 | */ |
526 | |
527 | /* |
528 | * The trampoline is called when the hrtimer expires. It schedules a tasklet |
529 | * to run __tasklet_hrtimer_trampoline() which in turn will call the intended |
530 | * hrtimer callback, but from softirq context. |
531 | */ |
532 | static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer) |
533 | { |
534 | struct tasklet_hrtimer *ttimer = |
535 | container_of(timer, struct tasklet_hrtimer, timer); |
536 | |
537 | tasklet_hi_schedule(&ttimer->tasklet); |
538 | return HRTIMER_NORESTART; |
539 | } |
540 | |
541 | /* |
542 | * Helper function which calls the hrtimer callback from |
543 | * tasklet/softirq context |
544 | */ |
545 | static void __tasklet_hrtimer_trampoline(unsigned long data) |
546 | { |
547 | struct tasklet_hrtimer *ttimer = (void *)data; |
548 | enum hrtimer_restart restart; |
549 | |
550 | restart = ttimer->function(&ttimer->timer); |
551 | if (restart != HRTIMER_NORESTART) |
552 | hrtimer_restart(&ttimer->timer); |
553 | } |
554 | |
555 | /** |
556 | * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks |
557 | * @ttimer: tasklet_hrtimer which is initialized |
558 | * @function: hrtimer callback funtion which gets called from softirq context |
559 | * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME) |
560 | * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL) |
561 | */ |
562 | void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer, |
563 | enum hrtimer_restart (*function)(struct hrtimer *), |
564 | clockid_t which_clock, enum hrtimer_mode mode) |
565 | { |
566 | hrtimer_init(&ttimer->timer, which_clock, mode); |
567 | ttimer->timer.function = __hrtimer_tasklet_trampoline; |
568 | tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline, |
569 | (unsigned long)ttimer); |
570 | ttimer->function = function; |
571 | } |
572 | EXPORT_SYMBOL_GPL(tasklet_hrtimer_init); |
573 | |
574 | /* |
575 | * Remote softirq bits |
576 | */ |
577 | |
578 | DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); |
579 | EXPORT_PER_CPU_SYMBOL(softirq_work_list); |
580 | |
581 | static void __local_trigger(struct call_single_data *cp, int softirq) |
582 | { |
583 | struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]); |
584 | |
585 | list_add_tail(&cp->list, head); |
586 | |
587 | /* Trigger the softirq only if the list was previously empty. */ |
588 | if (head->next == &cp->list) |
589 | raise_softirq_irqoff(softirq); |
590 | } |
591 | |
592 | #ifdef CONFIG_USE_GENERIC_SMP_HELPERS |
593 | static void remote_softirq_receive(void *data) |
594 | { |
595 | struct call_single_data *cp = data; |
596 | unsigned long flags; |
597 | int softirq; |
598 | |
599 | softirq = cp->priv; |
600 | |
601 | local_irq_save(flags); |
602 | __local_trigger(cp, softirq); |
603 | local_irq_restore(flags); |
604 | } |
605 | |
606 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) |
607 | { |
608 | if (cpu_online(cpu)) { |
609 | cp->func = remote_softirq_receive; |
610 | cp->info = cp; |
611 | cp->flags = 0; |
612 | cp->priv = softirq; |
613 | |
614 | __smp_call_function_single(cpu, cp, 0); |
615 | return 0; |
616 | } |
617 | return 1; |
618 | } |
619 | #else /* CONFIG_USE_GENERIC_SMP_HELPERS */ |
620 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) |
621 | { |
622 | return 1; |
623 | } |
624 | #endif |
625 | |
626 | /** |
627 | * __send_remote_softirq - try to schedule softirq work on a remote cpu |
628 | * @cp: private SMP call function data area |
629 | * @cpu: the remote cpu |
630 | * @this_cpu: the currently executing cpu |
631 | * @softirq: the softirq for the work |
632 | * |
633 | * Attempt to schedule softirq work on a remote cpu. If this cannot be |
634 | * done, the work is instead queued up on the local cpu. |
635 | * |
636 | * Interrupts must be disabled. |
637 | */ |
638 | void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq) |
639 | { |
640 | if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq)) |
641 | __local_trigger(cp, softirq); |
642 | } |
643 | EXPORT_SYMBOL(__send_remote_softirq); |
644 | |
645 | /** |
646 | * send_remote_softirq - try to schedule softirq work on a remote cpu |
647 | * @cp: private SMP call function data area |
648 | * @cpu: the remote cpu |
649 | * @softirq: the softirq for the work |
650 | * |
651 | * Like __send_remote_softirq except that disabling interrupts and |
652 | * computing the current cpu is done for the caller. |
653 | */ |
654 | void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq) |
655 | { |
656 | unsigned long flags; |
657 | int this_cpu; |
658 | |
659 | local_irq_save(flags); |
660 | this_cpu = smp_processor_id(); |
661 | __send_remote_softirq(cp, cpu, this_cpu, softirq); |
662 | local_irq_restore(flags); |
663 | } |
664 | EXPORT_SYMBOL(send_remote_softirq); |
665 | |
666 | static int __cpuinit remote_softirq_cpu_notify(struct notifier_block *self, |
667 | unsigned long action, void *hcpu) |
668 | { |
669 | /* |
670 | * If a CPU goes away, splice its entries to the current CPU |
671 | * and trigger a run of the softirq |
672 | */ |
673 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { |
674 | int cpu = (unsigned long) hcpu; |
675 | int i; |
676 | |
677 | local_irq_disable(); |
678 | for (i = 0; i < NR_SOFTIRQS; i++) { |
679 | struct list_head *head = &per_cpu(softirq_work_list[i], cpu); |
680 | struct list_head *local_head; |
681 | |
682 | if (list_empty(head)) |
683 | continue; |
684 | |
685 | local_head = &__get_cpu_var(softirq_work_list[i]); |
686 | list_splice_init(head, local_head); |
687 | raise_softirq_irqoff(i); |
688 | } |
689 | local_irq_enable(); |
690 | } |
691 | |
692 | return NOTIFY_OK; |
693 | } |
694 | |
695 | static struct notifier_block __cpuinitdata remote_softirq_cpu_notifier = { |
696 | .notifier_call = remote_softirq_cpu_notify, |
697 | }; |
698 | |
699 | void __init softirq_init(void) |
700 | { |
701 | int cpu; |
702 | |
703 | for_each_possible_cpu(cpu) { |
704 | int i; |
705 | |
706 | per_cpu(tasklet_vec, cpu).tail = |
707 | &per_cpu(tasklet_vec, cpu).head; |
708 | per_cpu(tasklet_hi_vec, cpu).tail = |
709 | &per_cpu(tasklet_hi_vec, cpu).head; |
710 | for (i = 0; i < NR_SOFTIRQS; i++) |
711 | INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu)); |
712 | } |
713 | |
714 | register_hotcpu_notifier(&remote_softirq_cpu_notifier); |
715 | |
716 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
717 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); |
718 | } |
719 | |
720 | static int run_ksoftirqd(void * __bind_cpu) |
721 | { |
722 | set_current_state(TASK_INTERRUPTIBLE); |
723 | |
724 | current->flags |= PF_KSOFTIRQD; |
725 | while (!kthread_should_stop()) { |
726 | preempt_disable(); |
727 | if (!local_softirq_pending()) { |
728 | preempt_enable_no_resched(); |
729 | schedule(); |
730 | preempt_disable(); |
731 | } |
732 | |
733 | __set_current_state(TASK_RUNNING); |
734 | |
735 | while (local_softirq_pending()) { |
736 | /* Preempt disable stops cpu going offline. |
737 | If already offline, we'll be on wrong CPU: |
738 | don't process */ |
739 | if (cpu_is_offline((long)__bind_cpu)) |
740 | goto wait_to_die; |
741 | do_softirq(); |
742 | preempt_enable_no_resched(); |
743 | cond_resched(); |
744 | preempt_disable(); |
745 | rcu_note_context_switch((long)__bind_cpu); |
746 | } |
747 | preempt_enable(); |
748 | set_current_state(TASK_INTERRUPTIBLE); |
749 | } |
750 | __set_current_state(TASK_RUNNING); |
751 | return 0; |
752 | |
753 | wait_to_die: |
754 | preempt_enable(); |
755 | /* Wait for kthread_stop */ |
756 | set_current_state(TASK_INTERRUPTIBLE); |
757 | while (!kthread_should_stop()) { |
758 | schedule(); |
759 | set_current_state(TASK_INTERRUPTIBLE); |
760 | } |
761 | __set_current_state(TASK_RUNNING); |
762 | return 0; |
763 | } |
764 | |
765 | #ifdef CONFIG_HOTPLUG_CPU |
766 | /* |
767 | * tasklet_kill_immediate is called to remove a tasklet which can already be |
768 | * scheduled for execution on @cpu. |
769 | * |
770 | * Unlike tasklet_kill, this function removes the tasklet |
771 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. |
772 | * |
773 | * When this function is called, @cpu must be in the CPU_DEAD state. |
774 | */ |
775 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) |
776 | { |
777 | struct tasklet_struct **i; |
778 | |
779 | BUG_ON(cpu_online(cpu)); |
780 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); |
781 | |
782 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) |
783 | return; |
784 | |
785 | /* CPU is dead, so no lock needed. */ |
786 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
787 | if (*i == t) { |
788 | *i = t->next; |
789 | /* If this was the tail element, move the tail ptr */ |
790 | if (*i == NULL) |
791 | per_cpu(tasklet_vec, cpu).tail = i; |
792 | return; |
793 | } |
794 | } |
795 | BUG(); |
796 | } |
797 | |
798 | static void takeover_tasklets(unsigned int cpu) |
799 | { |
800 | /* CPU is dead, so no lock needed. */ |
801 | local_irq_disable(); |
802 | |
803 | /* Find end, append list for that CPU. */ |
804 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
805 | *(__get_cpu_var(tasklet_vec).tail) = per_cpu(tasklet_vec, cpu).head; |
806 | __get_cpu_var(tasklet_vec).tail = per_cpu(tasklet_vec, cpu).tail; |
807 | per_cpu(tasklet_vec, cpu).head = NULL; |
808 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; |
809 | } |
810 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
811 | |
812 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
813 | *__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).head; |
814 | __get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).tail; |
815 | per_cpu(tasklet_hi_vec, cpu).head = NULL; |
816 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; |
817 | } |
818 | raise_softirq_irqoff(HI_SOFTIRQ); |
819 | |
820 | local_irq_enable(); |
821 | } |
822 | #endif /* CONFIG_HOTPLUG_CPU */ |
823 | |
824 | static int __cpuinit cpu_callback(struct notifier_block *nfb, |
825 | unsigned long action, |
826 | void *hcpu) |
827 | { |
828 | int hotcpu = (unsigned long)hcpu; |
829 | struct task_struct *p; |
830 | |
831 | switch (action) { |
832 | case CPU_UP_PREPARE: |
833 | case CPU_UP_PREPARE_FROZEN: |
834 | p = kthread_create(run_ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu); |
835 | if (IS_ERR(p)) { |
836 | printk("ksoftirqd for %i failed\n", hotcpu); |
837 | return notifier_from_errno(PTR_ERR(p)); |
838 | } |
839 | kthread_bind(p, hotcpu); |
840 | per_cpu(ksoftirqd, hotcpu) = p; |
841 | break; |
842 | case CPU_ONLINE: |
843 | case CPU_ONLINE_FROZEN: |
844 | wake_up_process(per_cpu(ksoftirqd, hotcpu)); |
845 | break; |
846 | #ifdef CONFIG_HOTPLUG_CPU |
847 | case CPU_UP_CANCELED: |
848 | case CPU_UP_CANCELED_FROZEN: |
849 | if (!per_cpu(ksoftirqd, hotcpu)) |
850 | break; |
851 | /* Unbind so it can run. Fall thru. */ |
852 | kthread_bind(per_cpu(ksoftirqd, hotcpu), |
853 | cpumask_any(cpu_online_mask)); |
854 | case CPU_DEAD: |
855 | case CPU_DEAD_FROZEN: { |
856 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
857 | |
858 | p = per_cpu(ksoftirqd, hotcpu); |
859 | per_cpu(ksoftirqd, hotcpu) = NULL; |
860 | sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); |
861 | kthread_stop(p); |
862 | takeover_tasklets(hotcpu); |
863 | break; |
864 | } |
865 | #endif /* CONFIG_HOTPLUG_CPU */ |
866 | } |
867 | return NOTIFY_OK; |
868 | } |
869 | |
870 | static struct notifier_block __cpuinitdata cpu_nfb = { |
871 | .notifier_call = cpu_callback |
872 | }; |
873 | |
874 | static __init int spawn_ksoftirqd(void) |
875 | { |
876 | void *cpu = (void *)(long)smp_processor_id(); |
877 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
878 | |
879 | BUG_ON(err != NOTIFY_OK); |
880 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
881 | register_cpu_notifier(&cpu_nfb); |
882 | return 0; |
883 | } |
884 | early_initcall(spawn_ksoftirqd); |
885 | |
886 | #ifdef CONFIG_SMP |
887 | /* |
888 | * Call a function on all processors |
889 | */ |
890 | int on_each_cpu(void (*func) (void *info), void *info, int wait) |
891 | { |
892 | int ret = 0; |
893 | |
894 | preempt_disable(); |
895 | ret = smp_call_function(func, info, wait); |
896 | local_irq_disable(); |
897 | func(info); |
898 | local_irq_enable(); |
899 | preempt_enable(); |
900 | return ret; |
901 | } |
902 | EXPORT_SYMBOL(on_each_cpu); |
903 | #endif |
904 | |
905 | /* |
906 | * [ These __weak aliases are kept in a separate compilation unit, so that |
907 | * GCC does not inline them incorrectly. ] |
908 | */ |
909 | |
910 | int __init __weak early_irq_init(void) |
911 | { |
912 | return 0; |
913 | } |
914 | |
915 | #ifdef CONFIG_GENERIC_HARDIRQS |
916 | int __init __weak arch_probe_nr_irqs(void) |
917 | { |
918 | return NR_IRQS_LEGACY; |
919 | } |
920 | |
921 | int __init __weak arch_early_irq_init(void) |
922 | { |
923 | return 0; |
924 | } |
925 | #endif |
926 |
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