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