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1da177e4 LT |
1 | /* |
2 | * linux/kernel/softirq.c | |
3 | * | |
4 | * Copyright (C) 1992 Linus Torvalds | |
5 | * | |
b10db7f0 PM |
6 | * Distribute under GPLv2. |
7 | * | |
8 | * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) | |
54514a70 DM |
9 | * |
10 | * Remote softirq infrastructure is by Jens Axboe. | |
1da177e4 LT |
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> | |
83144186 | 21 | #include <linux/freezer.h> |
1da177e4 LT |
22 | #include <linux/kthread.h> |
23 | #include <linux/rcupdate.h> | |
78eef01b | 24 | #include <linux/smp.h> |
79bf2bb3 | 25 | #include <linux/tick.h> |
1da177e4 LT |
26 | |
27 | #include <asm/irq.h> | |
28 | /* | |
29 | - No shared variables, all the data are CPU local. | |
30 | - If a softirq needs serialization, let it serialize itself | |
31 | by its own spinlocks. | |
32 | - Even if softirq is serialized, only local cpu is marked for | |
33 | execution. Hence, we get something sort of weak cpu binding. | |
34 | Though it is still not clear, will it result in better locality | |
35 | or will not. | |
36 | ||
37 | Examples: | |
38 | - NET RX softirq. It is multithreaded and does not require | |
39 | any global serialization. | |
40 | - NET TX softirq. It kicks software netdevice queues, hence | |
41 | it is logically serialized per device, but this serialization | |
42 | is invisible to common code. | |
43 | - Tasklets: serialized wrt itself. | |
44 | */ | |
45 | ||
46 | #ifndef __ARCH_IRQ_STAT | |
47 | irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned; | |
48 | EXPORT_SYMBOL(irq_stat); | |
49 | #endif | |
50 | ||
978b0116 | 51 | static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
1da177e4 LT |
52 | |
53 | static DEFINE_PER_CPU(struct task_struct *, ksoftirqd); | |
54 | ||
55 | /* | |
56 | * we cannot loop indefinitely here to avoid userspace starvation, | |
57 | * but we also don't want to introduce a worst case 1/HZ latency | |
58 | * to the pending events, so lets the scheduler to balance | |
59 | * the softirq load for us. | |
60 | */ | |
61 | static inline void wakeup_softirqd(void) | |
62 | { | |
63 | /* Interrupts are disabled: no need to stop preemption */ | |
64 | struct task_struct *tsk = __get_cpu_var(ksoftirqd); | |
65 | ||
66 | if (tsk && tsk->state != TASK_RUNNING) | |
67 | wake_up_process(tsk); | |
68 | } | |
69 | ||
de30a2b3 IM |
70 | /* |
71 | * This one is for softirq.c-internal use, | |
72 | * where hardirqs are disabled legitimately: | |
73 | */ | |
3c829c36 | 74 | #ifdef CONFIG_TRACE_IRQFLAGS |
de30a2b3 IM |
75 | static void __local_bh_disable(unsigned long ip) |
76 | { | |
77 | unsigned long flags; | |
78 | ||
79 | WARN_ON_ONCE(in_irq()); | |
80 | ||
81 | raw_local_irq_save(flags); | |
82 | add_preempt_count(SOFTIRQ_OFFSET); | |
83 | /* | |
84 | * Were softirqs turned off above: | |
85 | */ | |
86 | if (softirq_count() == SOFTIRQ_OFFSET) | |
87 | trace_softirqs_off(ip); | |
88 | raw_local_irq_restore(flags); | |
89 | } | |
3c829c36 TC |
90 | #else /* !CONFIG_TRACE_IRQFLAGS */ |
91 | static inline void __local_bh_disable(unsigned long ip) | |
92 | { | |
93 | add_preempt_count(SOFTIRQ_OFFSET); | |
94 | barrier(); | |
95 | } | |
96 | #endif /* CONFIG_TRACE_IRQFLAGS */ | |
de30a2b3 IM |
97 | |
98 | void local_bh_disable(void) | |
99 | { | |
100 | __local_bh_disable((unsigned long)__builtin_return_address(0)); | |
101 | } | |
102 | ||
103 | EXPORT_SYMBOL(local_bh_disable); | |
104 | ||
de30a2b3 IM |
105 | /* |
106 | * Special-case - softirqs can safely be enabled in | |
107 | * cond_resched_softirq(), or by __do_softirq(), | |
108 | * without processing still-pending softirqs: | |
109 | */ | |
110 | void _local_bh_enable(void) | |
111 | { | |
112 | WARN_ON_ONCE(in_irq()); | |
113 | WARN_ON_ONCE(!irqs_disabled()); | |
114 | ||
115 | if (softirq_count() == SOFTIRQ_OFFSET) | |
116 | trace_softirqs_on((unsigned long)__builtin_return_address(0)); | |
117 | sub_preempt_count(SOFTIRQ_OFFSET); | |
118 | } | |
119 | ||
120 | EXPORT_SYMBOL(_local_bh_enable); | |
121 | ||
0f476b6d | 122 | static inline void _local_bh_enable_ip(unsigned long ip) |
de30a2b3 | 123 | { |
0f476b6d | 124 | WARN_ON_ONCE(in_irq() || irqs_disabled()); |
3c829c36 | 125 | #ifdef CONFIG_TRACE_IRQFLAGS |
0f476b6d | 126 | local_irq_disable(); |
3c829c36 | 127 | #endif |
de30a2b3 IM |
128 | /* |
129 | * Are softirqs going to be turned on now: | |
130 | */ | |
131 | if (softirq_count() == SOFTIRQ_OFFSET) | |
0f476b6d | 132 | trace_softirqs_on(ip); |
de30a2b3 IM |
133 | /* |
134 | * Keep preemption disabled until we are done with | |
135 | * softirq processing: | |
136 | */ | |
137 | sub_preempt_count(SOFTIRQ_OFFSET - 1); | |
138 | ||
139 | if (unlikely(!in_interrupt() && local_softirq_pending())) | |
140 | do_softirq(); | |
141 | ||
142 | dec_preempt_count(); | |
3c829c36 | 143 | #ifdef CONFIG_TRACE_IRQFLAGS |
0f476b6d | 144 | local_irq_enable(); |
3c829c36 | 145 | #endif |
de30a2b3 IM |
146 | preempt_check_resched(); |
147 | } | |
0f476b6d JB |
148 | |
149 | void local_bh_enable(void) | |
150 | { | |
151 | _local_bh_enable_ip((unsigned long)__builtin_return_address(0)); | |
152 | } | |
de30a2b3 IM |
153 | EXPORT_SYMBOL(local_bh_enable); |
154 | ||
155 | void local_bh_enable_ip(unsigned long ip) | |
156 | { | |
0f476b6d | 157 | _local_bh_enable_ip(ip); |
de30a2b3 IM |
158 | } |
159 | EXPORT_SYMBOL(local_bh_enable_ip); | |
160 | ||
1da177e4 LT |
161 | /* |
162 | * We restart softirq processing MAX_SOFTIRQ_RESTART times, | |
163 | * and we fall back to softirqd after that. | |
164 | * | |
165 | * This number has been established via experimentation. | |
166 | * The two things to balance is latency against fairness - | |
167 | * we want to handle softirqs as soon as possible, but they | |
168 | * should not be able to lock up the box. | |
169 | */ | |
170 | #define MAX_SOFTIRQ_RESTART 10 | |
171 | ||
172 | asmlinkage void __do_softirq(void) | |
173 | { | |
174 | struct softirq_action *h; | |
175 | __u32 pending; | |
176 | int max_restart = MAX_SOFTIRQ_RESTART; | |
177 | int cpu; | |
178 | ||
179 | pending = local_softirq_pending(); | |
829035fd PM |
180 | account_system_vtime(current); |
181 | ||
de30a2b3 IM |
182 | __local_bh_disable((unsigned long)__builtin_return_address(0)); |
183 | trace_softirq_enter(); | |
1da177e4 | 184 | |
1da177e4 LT |
185 | cpu = smp_processor_id(); |
186 | restart: | |
187 | /* Reset the pending bitmask before enabling irqs */ | |
3f74478b | 188 | set_softirq_pending(0); |
1da177e4 | 189 | |
c70f5d66 | 190 | local_irq_enable(); |
1da177e4 LT |
191 | |
192 | h = softirq_vec; | |
193 | ||
194 | do { | |
195 | if (pending & 1) { | |
8e85b4b5 TG |
196 | int prev_count = preempt_count(); |
197 | ||
1da177e4 | 198 | h->action(h); |
8e85b4b5 TG |
199 | |
200 | if (unlikely(prev_count != preempt_count())) { | |
1c95e1b6 | 201 | printk(KERN_ERR "huh, entered softirq %td %p" |
8e85b4b5 TG |
202 | "with preempt_count %08x," |
203 | " exited with %08x?\n", h - softirq_vec, | |
204 | h->action, prev_count, preempt_count()); | |
205 | preempt_count() = prev_count; | |
206 | } | |
207 | ||
1da177e4 LT |
208 | rcu_bh_qsctr_inc(cpu); |
209 | } | |
210 | h++; | |
211 | pending >>= 1; | |
212 | } while (pending); | |
213 | ||
c70f5d66 | 214 | local_irq_disable(); |
1da177e4 LT |
215 | |
216 | pending = local_softirq_pending(); | |
217 | if (pending && --max_restart) | |
218 | goto restart; | |
219 | ||
220 | if (pending) | |
221 | wakeup_softirqd(); | |
222 | ||
de30a2b3 | 223 | trace_softirq_exit(); |
829035fd PM |
224 | |
225 | account_system_vtime(current); | |
de30a2b3 | 226 | _local_bh_enable(); |
1da177e4 LT |
227 | } |
228 | ||
229 | #ifndef __ARCH_HAS_DO_SOFTIRQ | |
230 | ||
231 | asmlinkage void do_softirq(void) | |
232 | { | |
233 | __u32 pending; | |
234 | unsigned long flags; | |
235 | ||
236 | if (in_interrupt()) | |
237 | return; | |
238 | ||
239 | local_irq_save(flags); | |
240 | ||
241 | pending = local_softirq_pending(); | |
242 | ||
243 | if (pending) | |
244 | __do_softirq(); | |
245 | ||
246 | local_irq_restore(flags); | |
247 | } | |
248 | ||
1da177e4 LT |
249 | #endif |
250 | ||
dde4b2b5 IM |
251 | /* |
252 | * Enter an interrupt context. | |
253 | */ | |
254 | void irq_enter(void) | |
255 | { | |
6378ddb5 | 256 | int cpu = smp_processor_id(); |
719254fa | 257 | |
64db4cff | 258 | rcu_irq_enter(); |
ee5f80a9 TG |
259 | if (idle_cpu(cpu) && !in_interrupt()) { |
260 | __irq_enter(); | |
719254fa | 261 | tick_check_idle(cpu); |
ee5f80a9 TG |
262 | } else |
263 | __irq_enter(); | |
dde4b2b5 IM |
264 | } |
265 | ||
1da177e4 LT |
266 | #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED |
267 | # define invoke_softirq() __do_softirq() | |
268 | #else | |
269 | # define invoke_softirq() do_softirq() | |
270 | #endif | |
271 | ||
272 | /* | |
273 | * Exit an interrupt context. Process softirqs if needed and possible: | |
274 | */ | |
275 | void irq_exit(void) | |
276 | { | |
277 | account_system_vtime(current); | |
de30a2b3 | 278 | trace_hardirq_exit(); |
1da177e4 LT |
279 | sub_preempt_count(IRQ_EXIT_OFFSET); |
280 | if (!in_interrupt() && local_softirq_pending()) | |
281 | invoke_softirq(); | |
79bf2bb3 TG |
282 | |
283 | #ifdef CONFIG_NO_HZ | |
284 | /* Make sure that timer wheel updates are propagated */ | |
2232c2d8 | 285 | rcu_irq_exit(); |
64db4cff PM |
286 | if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched()) |
287 | tick_nohz_stop_sched_tick(0); | |
79bf2bb3 | 288 | #endif |
1da177e4 LT |
289 | preempt_enable_no_resched(); |
290 | } | |
291 | ||
292 | /* | |
293 | * This function must run with irqs disabled! | |
294 | */ | |
7ad5b3a5 | 295 | inline void raise_softirq_irqoff(unsigned int nr) |
1da177e4 LT |
296 | { |
297 | __raise_softirq_irqoff(nr); | |
298 | ||
299 | /* | |
300 | * If we're in an interrupt or softirq, we're done | |
301 | * (this also catches softirq-disabled code). We will | |
302 | * actually run the softirq once we return from | |
303 | * the irq or softirq. | |
304 | * | |
305 | * Otherwise we wake up ksoftirqd to make sure we | |
306 | * schedule the softirq soon. | |
307 | */ | |
308 | if (!in_interrupt()) | |
309 | wakeup_softirqd(); | |
310 | } | |
311 | ||
7ad5b3a5 | 312 | void raise_softirq(unsigned int nr) |
1da177e4 LT |
313 | { |
314 | unsigned long flags; | |
315 | ||
316 | local_irq_save(flags); | |
317 | raise_softirq_irqoff(nr); | |
318 | local_irq_restore(flags); | |
319 | } | |
320 | ||
962cf36c | 321 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
1da177e4 | 322 | { |
1da177e4 LT |
323 | softirq_vec[nr].action = action; |
324 | } | |
325 | ||
1da177e4 LT |
326 | /* Tasklets */ |
327 | struct tasklet_head | |
328 | { | |
48f20a9a OJ |
329 | struct tasklet_struct *head; |
330 | struct tasklet_struct **tail; | |
1da177e4 LT |
331 | }; |
332 | ||
4620b49f VN |
333 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
334 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); | |
1da177e4 | 335 | |
7ad5b3a5 | 336 | void __tasklet_schedule(struct tasklet_struct *t) |
1da177e4 LT |
337 | { |
338 | unsigned long flags; | |
339 | ||
340 | local_irq_save(flags); | |
48f20a9a OJ |
341 | t->next = NULL; |
342 | *__get_cpu_var(tasklet_vec).tail = t; | |
343 | __get_cpu_var(tasklet_vec).tail = &(t->next); | |
1da177e4 LT |
344 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
345 | local_irq_restore(flags); | |
346 | } | |
347 | ||
348 | EXPORT_SYMBOL(__tasklet_schedule); | |
349 | ||
7ad5b3a5 | 350 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
1da177e4 LT |
351 | { |
352 | unsigned long flags; | |
353 | ||
354 | local_irq_save(flags); | |
48f20a9a OJ |
355 | t->next = NULL; |
356 | *__get_cpu_var(tasklet_hi_vec).tail = t; | |
357 | __get_cpu_var(tasklet_hi_vec).tail = &(t->next); | |
1da177e4 LT |
358 | raise_softirq_irqoff(HI_SOFTIRQ); |
359 | local_irq_restore(flags); | |
360 | } | |
361 | ||
362 | EXPORT_SYMBOL(__tasklet_hi_schedule); | |
363 | ||
364 | static void tasklet_action(struct softirq_action *a) | |
365 | { | |
366 | struct tasklet_struct *list; | |
367 | ||
368 | local_irq_disable(); | |
48f20a9a OJ |
369 | list = __get_cpu_var(tasklet_vec).head; |
370 | __get_cpu_var(tasklet_vec).head = NULL; | |
371 | __get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head; | |
1da177e4 LT |
372 | local_irq_enable(); |
373 | ||
374 | while (list) { | |
375 | struct tasklet_struct *t = list; | |
376 | ||
377 | list = list->next; | |
378 | ||
379 | if (tasklet_trylock(t)) { | |
380 | if (!atomic_read(&t->count)) { | |
381 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) | |
382 | BUG(); | |
383 | t->func(t->data); | |
384 | tasklet_unlock(t); | |
385 | continue; | |
386 | } | |
387 | tasklet_unlock(t); | |
388 | } | |
389 | ||
390 | local_irq_disable(); | |
48f20a9a OJ |
391 | t->next = NULL; |
392 | *__get_cpu_var(tasklet_vec).tail = t; | |
393 | __get_cpu_var(tasklet_vec).tail = &(t->next); | |
1da177e4 LT |
394 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
395 | local_irq_enable(); | |
396 | } | |
397 | } | |
398 | ||
399 | static void tasklet_hi_action(struct softirq_action *a) | |
400 | { | |
401 | struct tasklet_struct *list; | |
402 | ||
403 | local_irq_disable(); | |
48f20a9a OJ |
404 | list = __get_cpu_var(tasklet_hi_vec).head; |
405 | __get_cpu_var(tasklet_hi_vec).head = NULL; | |
406 | __get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head; | |
1da177e4 LT |
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(); | |
48f20a9a OJ |
426 | t->next = NULL; |
427 | *__get_cpu_var(tasklet_hi_vec).tail = t; | |
428 | __get_cpu_var(tasklet_hi_vec).tail = &(t->next); | |
1da177e4 LT |
429 | __raise_softirq_irqoff(HI_SOFTIRQ); |
430 | local_irq_enable(); | |
431 | } | |
432 | } | |
433 | ||
434 | ||
435 | void tasklet_init(struct tasklet_struct *t, | |
436 | void (*func)(unsigned long), unsigned long data) | |
437 | { | |
438 | t->next = NULL; | |
439 | t->state = 0; | |
440 | atomic_set(&t->count, 0); | |
441 | t->func = func; | |
442 | t->data = data; | |
443 | } | |
444 | ||
445 | EXPORT_SYMBOL(tasklet_init); | |
446 | ||
447 | void tasklet_kill(struct tasklet_struct *t) | |
448 | { | |
449 | if (in_interrupt()) | |
450 | printk("Attempt to kill tasklet from interrupt\n"); | |
451 | ||
452 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { | |
453 | do | |
454 | yield(); | |
455 | while (test_bit(TASKLET_STATE_SCHED, &t->state)); | |
456 | } | |
457 | tasklet_unlock_wait(t); | |
458 | clear_bit(TASKLET_STATE_SCHED, &t->state); | |
459 | } | |
460 | ||
461 | EXPORT_SYMBOL(tasklet_kill); | |
462 | ||
54514a70 DM |
463 | DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); |
464 | EXPORT_PER_CPU_SYMBOL(softirq_work_list); | |
465 | ||
466 | static void __local_trigger(struct call_single_data *cp, int softirq) | |
467 | { | |
468 | struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]); | |
469 | ||
470 | list_add_tail(&cp->list, head); | |
471 | ||
472 | /* Trigger the softirq only if the list was previously empty. */ | |
473 | if (head->next == &cp->list) | |
474 | raise_softirq_irqoff(softirq); | |
475 | } | |
476 | ||
477 | #ifdef CONFIG_USE_GENERIC_SMP_HELPERS | |
478 | static void remote_softirq_receive(void *data) | |
479 | { | |
480 | struct call_single_data *cp = data; | |
481 | unsigned long flags; | |
482 | int softirq; | |
483 | ||
484 | softirq = cp->priv; | |
485 | ||
486 | local_irq_save(flags); | |
487 | __local_trigger(cp, softirq); | |
488 | local_irq_restore(flags); | |
489 | } | |
490 | ||
491 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
492 | { | |
493 | if (cpu_online(cpu)) { | |
494 | cp->func = remote_softirq_receive; | |
495 | cp->info = cp; | |
496 | cp->flags = 0; | |
497 | cp->priv = softirq; | |
498 | ||
499 | __smp_call_function_single(cpu, cp); | |
500 | return 0; | |
501 | } | |
502 | return 1; | |
503 | } | |
504 | #else /* CONFIG_USE_GENERIC_SMP_HELPERS */ | |
505 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
506 | { | |
507 | return 1; | |
508 | } | |
509 | #endif | |
510 | ||
511 | /** | |
512 | * __send_remote_softirq - try to schedule softirq work on a remote cpu | |
513 | * @cp: private SMP call function data area | |
514 | * @cpu: the remote cpu | |
515 | * @this_cpu: the currently executing cpu | |
516 | * @softirq: the softirq for the work | |
517 | * | |
518 | * Attempt to schedule softirq work on a remote cpu. If this cannot be | |
519 | * done, the work is instead queued up on the local cpu. | |
520 | * | |
521 | * Interrupts must be disabled. | |
522 | */ | |
523 | void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq) | |
524 | { | |
525 | if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq)) | |
526 | __local_trigger(cp, softirq); | |
527 | } | |
528 | EXPORT_SYMBOL(__send_remote_softirq); | |
529 | ||
530 | /** | |
531 | * send_remote_softirq - try to schedule softirq work on a remote cpu | |
532 | * @cp: private SMP call function data area | |
533 | * @cpu: the remote cpu | |
534 | * @softirq: the softirq for the work | |
535 | * | |
536 | * Like __send_remote_softirq except that disabling interrupts and | |
537 | * computing the current cpu is done for the caller. | |
538 | */ | |
539 | void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
540 | { | |
541 | unsigned long flags; | |
542 | int this_cpu; | |
543 | ||
544 | local_irq_save(flags); | |
545 | this_cpu = smp_processor_id(); | |
546 | __send_remote_softirq(cp, cpu, this_cpu, softirq); | |
547 | local_irq_restore(flags); | |
548 | } | |
549 | EXPORT_SYMBOL(send_remote_softirq); | |
550 | ||
551 | static int __cpuinit remote_softirq_cpu_notify(struct notifier_block *self, | |
552 | unsigned long action, void *hcpu) | |
553 | { | |
554 | /* | |
555 | * If a CPU goes away, splice its entries to the current CPU | |
556 | * and trigger a run of the softirq | |
557 | */ | |
558 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { | |
559 | int cpu = (unsigned long) hcpu; | |
560 | int i; | |
561 | ||
562 | local_irq_disable(); | |
563 | for (i = 0; i < NR_SOFTIRQS; i++) { | |
564 | struct list_head *head = &per_cpu(softirq_work_list[i], cpu); | |
565 | struct list_head *local_head; | |
566 | ||
567 | if (list_empty(head)) | |
568 | continue; | |
569 | ||
570 | local_head = &__get_cpu_var(softirq_work_list[i]); | |
571 | list_splice_init(head, local_head); | |
572 | raise_softirq_irqoff(i); | |
573 | } | |
574 | local_irq_enable(); | |
575 | } | |
576 | ||
577 | return NOTIFY_OK; | |
578 | } | |
579 | ||
580 | static struct notifier_block __cpuinitdata remote_softirq_cpu_notifier = { | |
581 | .notifier_call = remote_softirq_cpu_notify, | |
582 | }; | |
583 | ||
1da177e4 LT |
584 | void __init softirq_init(void) |
585 | { | |
48f20a9a OJ |
586 | int cpu; |
587 | ||
588 | for_each_possible_cpu(cpu) { | |
54514a70 DM |
589 | int i; |
590 | ||
48f20a9a OJ |
591 | per_cpu(tasklet_vec, cpu).tail = |
592 | &per_cpu(tasklet_vec, cpu).head; | |
593 | per_cpu(tasklet_hi_vec, cpu).tail = | |
594 | &per_cpu(tasklet_hi_vec, cpu).head; | |
54514a70 DM |
595 | for (i = 0; i < NR_SOFTIRQS; i++) |
596 | INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu)); | |
48f20a9a OJ |
597 | } |
598 | ||
54514a70 DM |
599 | register_hotcpu_notifier(&remote_softirq_cpu_notifier); |
600 | ||
962cf36c CM |
601 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
602 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); | |
1da177e4 LT |
603 | } |
604 | ||
605 | static int ksoftirqd(void * __bind_cpu) | |
606 | { | |
1da177e4 LT |
607 | set_current_state(TASK_INTERRUPTIBLE); |
608 | ||
609 | while (!kthread_should_stop()) { | |
610 | preempt_disable(); | |
611 | if (!local_softirq_pending()) { | |
612 | preempt_enable_no_resched(); | |
613 | schedule(); | |
614 | preempt_disable(); | |
615 | } | |
616 | ||
617 | __set_current_state(TASK_RUNNING); | |
618 | ||
619 | while (local_softirq_pending()) { | |
620 | /* Preempt disable stops cpu going offline. | |
621 | If already offline, we'll be on wrong CPU: | |
622 | don't process */ | |
623 | if (cpu_is_offline((long)__bind_cpu)) | |
624 | goto wait_to_die; | |
625 | do_softirq(); | |
626 | preempt_enable_no_resched(); | |
627 | cond_resched(); | |
628 | preempt_disable(); | |
629 | } | |
630 | preempt_enable(); | |
631 | set_current_state(TASK_INTERRUPTIBLE); | |
632 | } | |
633 | __set_current_state(TASK_RUNNING); | |
634 | return 0; | |
635 | ||
636 | wait_to_die: | |
637 | preempt_enable(); | |
638 | /* Wait for kthread_stop */ | |
639 | set_current_state(TASK_INTERRUPTIBLE); | |
640 | while (!kthread_should_stop()) { | |
641 | schedule(); | |
642 | set_current_state(TASK_INTERRUPTIBLE); | |
643 | } | |
644 | __set_current_state(TASK_RUNNING); | |
645 | return 0; | |
646 | } | |
647 | ||
648 | #ifdef CONFIG_HOTPLUG_CPU | |
649 | /* | |
650 | * tasklet_kill_immediate is called to remove a tasklet which can already be | |
651 | * scheduled for execution on @cpu. | |
652 | * | |
653 | * Unlike tasklet_kill, this function removes the tasklet | |
654 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. | |
655 | * | |
656 | * When this function is called, @cpu must be in the CPU_DEAD state. | |
657 | */ | |
658 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) | |
659 | { | |
660 | struct tasklet_struct **i; | |
661 | ||
662 | BUG_ON(cpu_online(cpu)); | |
663 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); | |
664 | ||
665 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) | |
666 | return; | |
667 | ||
668 | /* CPU is dead, so no lock needed. */ | |
48f20a9a | 669 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
1da177e4 LT |
670 | if (*i == t) { |
671 | *i = t->next; | |
48f20a9a OJ |
672 | /* If this was the tail element, move the tail ptr */ |
673 | if (*i == NULL) | |
674 | per_cpu(tasklet_vec, cpu).tail = i; | |
1da177e4 LT |
675 | return; |
676 | } | |
677 | } | |
678 | BUG(); | |
679 | } | |
680 | ||
681 | static void takeover_tasklets(unsigned int cpu) | |
682 | { | |
1da177e4 LT |
683 | /* CPU is dead, so no lock needed. */ |
684 | local_irq_disable(); | |
685 | ||
686 | /* Find end, append list for that CPU. */ | |
e5e41723 CB |
687 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
688 | *(__get_cpu_var(tasklet_vec).tail) = per_cpu(tasklet_vec, cpu).head; | |
689 | __get_cpu_var(tasklet_vec).tail = per_cpu(tasklet_vec, cpu).tail; | |
690 | per_cpu(tasklet_vec, cpu).head = NULL; | |
691 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; | |
692 | } | |
1da177e4 LT |
693 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
694 | ||
e5e41723 CB |
695 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
696 | *__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).head; | |
697 | __get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).tail; | |
698 | per_cpu(tasklet_hi_vec, cpu).head = NULL; | |
699 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; | |
700 | } | |
1da177e4 LT |
701 | raise_softirq_irqoff(HI_SOFTIRQ); |
702 | ||
703 | local_irq_enable(); | |
704 | } | |
705 | #endif /* CONFIG_HOTPLUG_CPU */ | |
706 | ||
8c78f307 | 707 | static int __cpuinit cpu_callback(struct notifier_block *nfb, |
1da177e4 LT |
708 | unsigned long action, |
709 | void *hcpu) | |
710 | { | |
711 | int hotcpu = (unsigned long)hcpu; | |
712 | struct task_struct *p; | |
713 | ||
714 | switch (action) { | |
715 | case CPU_UP_PREPARE: | |
8bb78442 | 716 | case CPU_UP_PREPARE_FROZEN: |
1da177e4 LT |
717 | p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu); |
718 | if (IS_ERR(p)) { | |
719 | printk("ksoftirqd for %i failed\n", hotcpu); | |
720 | return NOTIFY_BAD; | |
721 | } | |
722 | kthread_bind(p, hotcpu); | |
723 | per_cpu(ksoftirqd, hotcpu) = p; | |
724 | break; | |
725 | case CPU_ONLINE: | |
8bb78442 | 726 | case CPU_ONLINE_FROZEN: |
1da177e4 LT |
727 | wake_up_process(per_cpu(ksoftirqd, hotcpu)); |
728 | break; | |
729 | #ifdef CONFIG_HOTPLUG_CPU | |
730 | case CPU_UP_CANCELED: | |
8bb78442 | 731 | case CPU_UP_CANCELED_FROZEN: |
fc75cdfa HC |
732 | if (!per_cpu(ksoftirqd, hotcpu)) |
733 | break; | |
1da177e4 | 734 | /* Unbind so it can run. Fall thru. */ |
a4c4af7c HC |
735 | kthread_bind(per_cpu(ksoftirqd, hotcpu), |
736 | any_online_cpu(cpu_online_map)); | |
1da177e4 | 737 | case CPU_DEAD: |
1c6b4aa9 ST |
738 | case CPU_DEAD_FROZEN: { |
739 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; | |
740 | ||
1da177e4 LT |
741 | p = per_cpu(ksoftirqd, hotcpu); |
742 | per_cpu(ksoftirqd, hotcpu) = NULL; | |
961ccddd | 743 | sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); |
1da177e4 LT |
744 | kthread_stop(p); |
745 | takeover_tasklets(hotcpu); | |
746 | break; | |
1c6b4aa9 | 747 | } |
1da177e4 LT |
748 | #endif /* CONFIG_HOTPLUG_CPU */ |
749 | } | |
750 | return NOTIFY_OK; | |
751 | } | |
752 | ||
8c78f307 | 753 | static struct notifier_block __cpuinitdata cpu_nfb = { |
1da177e4 LT |
754 | .notifier_call = cpu_callback |
755 | }; | |
756 | ||
7babe8db | 757 | static __init int spawn_ksoftirqd(void) |
1da177e4 LT |
758 | { |
759 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 AM |
760 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
761 | ||
762 | BUG_ON(err == NOTIFY_BAD); | |
1da177e4 LT |
763 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
764 | register_cpu_notifier(&cpu_nfb); | |
765 | return 0; | |
766 | } | |
7babe8db | 767 | early_initcall(spawn_ksoftirqd); |
78eef01b AM |
768 | |
769 | #ifdef CONFIG_SMP | |
770 | /* | |
771 | * Call a function on all processors | |
772 | */ | |
15c8b6c1 | 773 | int on_each_cpu(void (*func) (void *info), void *info, int wait) |
78eef01b AM |
774 | { |
775 | int ret = 0; | |
776 | ||
777 | preempt_disable(); | |
8691e5a8 | 778 | ret = smp_call_function(func, info, wait); |
78eef01b AM |
779 | local_irq_disable(); |
780 | func(info); | |
781 | local_irq_enable(); | |
782 | preempt_enable(); | |
783 | return ret; | |
784 | } | |
785 | EXPORT_SYMBOL(on_each_cpu); | |
786 | #endif |