Commit | Line | Data |
---|---|---|
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 | ||
105 | void __local_bh_enable(void) | |
106 | { | |
107 | WARN_ON_ONCE(in_irq()); | |
108 | ||
109 | /* | |
110 | * softirqs should never be enabled by __local_bh_enable(), | |
111 | * it always nests inside local_bh_enable() sections: | |
112 | */ | |
113 | WARN_ON_ONCE(softirq_count() == SOFTIRQ_OFFSET); | |
114 | ||
115 | sub_preempt_count(SOFTIRQ_OFFSET); | |
116 | } | |
117 | EXPORT_SYMBOL_GPL(__local_bh_enable); | |
118 | ||
119 | /* | |
120 | * Special-case - softirqs can safely be enabled in | |
121 | * cond_resched_softirq(), or by __do_softirq(), | |
122 | * without processing still-pending softirqs: | |
123 | */ | |
124 | void _local_bh_enable(void) | |
125 | { | |
126 | WARN_ON_ONCE(in_irq()); | |
127 | WARN_ON_ONCE(!irqs_disabled()); | |
128 | ||
129 | if (softirq_count() == SOFTIRQ_OFFSET) | |
130 | trace_softirqs_on((unsigned long)__builtin_return_address(0)); | |
131 | sub_preempt_count(SOFTIRQ_OFFSET); | |
132 | } | |
133 | ||
134 | EXPORT_SYMBOL(_local_bh_enable); | |
135 | ||
0f476b6d | 136 | static inline void _local_bh_enable_ip(unsigned long ip) |
de30a2b3 | 137 | { |
0f476b6d | 138 | WARN_ON_ONCE(in_irq() || irqs_disabled()); |
3c829c36 | 139 | #ifdef CONFIG_TRACE_IRQFLAGS |
0f476b6d | 140 | local_irq_disable(); |
3c829c36 | 141 | #endif |
de30a2b3 IM |
142 | /* |
143 | * Are softirqs going to be turned on now: | |
144 | */ | |
145 | if (softirq_count() == SOFTIRQ_OFFSET) | |
0f476b6d | 146 | trace_softirqs_on(ip); |
de30a2b3 IM |
147 | /* |
148 | * Keep preemption disabled until we are done with | |
149 | * softirq processing: | |
150 | */ | |
151 | sub_preempt_count(SOFTIRQ_OFFSET - 1); | |
152 | ||
153 | if (unlikely(!in_interrupt() && local_softirq_pending())) | |
154 | do_softirq(); | |
155 | ||
156 | dec_preempt_count(); | |
3c829c36 | 157 | #ifdef CONFIG_TRACE_IRQFLAGS |
0f476b6d | 158 | local_irq_enable(); |
3c829c36 | 159 | #endif |
de30a2b3 IM |
160 | preempt_check_resched(); |
161 | } | |
0f476b6d JB |
162 | |
163 | void local_bh_enable(void) | |
164 | { | |
165 | _local_bh_enable_ip((unsigned long)__builtin_return_address(0)); | |
166 | } | |
de30a2b3 IM |
167 | EXPORT_SYMBOL(local_bh_enable); |
168 | ||
169 | void local_bh_enable_ip(unsigned long ip) | |
170 | { | |
0f476b6d | 171 | _local_bh_enable_ip(ip); |
de30a2b3 IM |
172 | } |
173 | EXPORT_SYMBOL(local_bh_enable_ip); | |
174 | ||
1da177e4 LT |
175 | /* |
176 | * We restart softirq processing MAX_SOFTIRQ_RESTART times, | |
177 | * and we fall back to softirqd after that. | |
178 | * | |
179 | * This number has been established via experimentation. | |
180 | * The two things to balance is latency against fairness - | |
181 | * we want to handle softirqs as soon as possible, but they | |
182 | * should not be able to lock up the box. | |
183 | */ | |
184 | #define MAX_SOFTIRQ_RESTART 10 | |
185 | ||
186 | asmlinkage void __do_softirq(void) | |
187 | { | |
188 | struct softirq_action *h; | |
189 | __u32 pending; | |
190 | int max_restart = MAX_SOFTIRQ_RESTART; | |
191 | int cpu; | |
192 | ||
193 | pending = local_softirq_pending(); | |
829035fd PM |
194 | account_system_vtime(current); |
195 | ||
de30a2b3 IM |
196 | __local_bh_disable((unsigned long)__builtin_return_address(0)); |
197 | trace_softirq_enter(); | |
1da177e4 | 198 | |
1da177e4 LT |
199 | cpu = smp_processor_id(); |
200 | restart: | |
201 | /* Reset the pending bitmask before enabling irqs */ | |
3f74478b | 202 | set_softirq_pending(0); |
1da177e4 | 203 | |
c70f5d66 | 204 | local_irq_enable(); |
1da177e4 LT |
205 | |
206 | h = softirq_vec; | |
207 | ||
208 | do { | |
209 | if (pending & 1) { | |
8e85b4b5 TG |
210 | int prev_count = preempt_count(); |
211 | ||
1da177e4 | 212 | h->action(h); |
8e85b4b5 TG |
213 | |
214 | if (unlikely(prev_count != preempt_count())) { | |
1c95e1b6 | 215 | printk(KERN_ERR "huh, entered softirq %td %p" |
8e85b4b5 TG |
216 | "with preempt_count %08x," |
217 | " exited with %08x?\n", h - softirq_vec, | |
218 | h->action, prev_count, preempt_count()); | |
219 | preempt_count() = prev_count; | |
220 | } | |
221 | ||
1da177e4 LT |
222 | rcu_bh_qsctr_inc(cpu); |
223 | } | |
224 | h++; | |
225 | pending >>= 1; | |
226 | } while (pending); | |
227 | ||
c70f5d66 | 228 | local_irq_disable(); |
1da177e4 LT |
229 | |
230 | pending = local_softirq_pending(); | |
231 | if (pending && --max_restart) | |
232 | goto restart; | |
233 | ||
234 | if (pending) | |
235 | wakeup_softirqd(); | |
236 | ||
de30a2b3 | 237 | trace_softirq_exit(); |
829035fd PM |
238 | |
239 | account_system_vtime(current); | |
de30a2b3 | 240 | _local_bh_enable(); |
1da177e4 LT |
241 | } |
242 | ||
243 | #ifndef __ARCH_HAS_DO_SOFTIRQ | |
244 | ||
245 | asmlinkage void do_softirq(void) | |
246 | { | |
247 | __u32 pending; | |
248 | unsigned long flags; | |
249 | ||
250 | if (in_interrupt()) | |
251 | return; | |
252 | ||
253 | local_irq_save(flags); | |
254 | ||
255 | pending = local_softirq_pending(); | |
256 | ||
257 | if (pending) | |
258 | __do_softirq(); | |
259 | ||
260 | local_irq_restore(flags); | |
261 | } | |
262 | ||
1da177e4 LT |
263 | #endif |
264 | ||
dde4b2b5 IM |
265 | /* |
266 | * Enter an interrupt context. | |
267 | */ | |
268 | void irq_enter(void) | |
269 | { | |
6378ddb5 VP |
270 | #ifdef CONFIG_NO_HZ |
271 | int cpu = smp_processor_id(); | |
272 | if (idle_cpu(cpu) && !in_interrupt()) | |
273 | tick_nohz_stop_idle(cpu); | |
274 | #endif | |
79bf2bb3 TG |
275 | __irq_enter(); |
276 | #ifdef CONFIG_NO_HZ | |
6378ddb5 | 277 | if (idle_cpu(cpu)) |
79bf2bb3 TG |
278 | tick_nohz_update_jiffies(); |
279 | #endif | |
dde4b2b5 IM |
280 | } |
281 | ||
1da177e4 LT |
282 | #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED |
283 | # define invoke_softirq() __do_softirq() | |
284 | #else | |
285 | # define invoke_softirq() do_softirq() | |
286 | #endif | |
287 | ||
288 | /* | |
289 | * Exit an interrupt context. Process softirqs if needed and possible: | |
290 | */ | |
291 | void irq_exit(void) | |
292 | { | |
293 | account_system_vtime(current); | |
de30a2b3 | 294 | trace_hardirq_exit(); |
1da177e4 LT |
295 | sub_preempt_count(IRQ_EXIT_OFFSET); |
296 | if (!in_interrupt() && local_softirq_pending()) | |
297 | invoke_softirq(); | |
79bf2bb3 TG |
298 | |
299 | #ifdef CONFIG_NO_HZ | |
300 | /* Make sure that timer wheel updates are propagated */ | |
301 | if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched()) | |
b8f8c3cf | 302 | tick_nohz_stop_sched_tick(0); |
2232c2d8 | 303 | rcu_irq_exit(); |
79bf2bb3 | 304 | #endif |
1da177e4 LT |
305 | preempt_enable_no_resched(); |
306 | } | |
307 | ||
308 | /* | |
309 | * This function must run with irqs disabled! | |
310 | */ | |
7ad5b3a5 | 311 | inline void raise_softirq_irqoff(unsigned int nr) |
1da177e4 LT |
312 | { |
313 | __raise_softirq_irqoff(nr); | |
314 | ||
315 | /* | |
316 | * If we're in an interrupt or softirq, we're done | |
317 | * (this also catches softirq-disabled code). We will | |
318 | * actually run the softirq once we return from | |
319 | * the irq or softirq. | |
320 | * | |
321 | * Otherwise we wake up ksoftirqd to make sure we | |
322 | * schedule the softirq soon. | |
323 | */ | |
324 | if (!in_interrupt()) | |
325 | wakeup_softirqd(); | |
326 | } | |
327 | ||
7ad5b3a5 | 328 | void raise_softirq(unsigned int nr) |
1da177e4 LT |
329 | { |
330 | unsigned long flags; | |
331 | ||
332 | local_irq_save(flags); | |
333 | raise_softirq_irqoff(nr); | |
334 | local_irq_restore(flags); | |
335 | } | |
336 | ||
962cf36c | 337 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
1da177e4 | 338 | { |
1da177e4 LT |
339 | softirq_vec[nr].action = action; |
340 | } | |
341 | ||
1da177e4 LT |
342 | /* Tasklets */ |
343 | struct tasklet_head | |
344 | { | |
48f20a9a OJ |
345 | struct tasklet_struct *head; |
346 | struct tasklet_struct **tail; | |
1da177e4 LT |
347 | }; |
348 | ||
4620b49f VN |
349 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
350 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); | |
1da177e4 | 351 | |
7ad5b3a5 | 352 | void __tasklet_schedule(struct tasklet_struct *t) |
1da177e4 LT |
353 | { |
354 | unsigned long flags; | |
355 | ||
356 | local_irq_save(flags); | |
48f20a9a OJ |
357 | t->next = NULL; |
358 | *__get_cpu_var(tasklet_vec).tail = t; | |
359 | __get_cpu_var(tasklet_vec).tail = &(t->next); | |
1da177e4 LT |
360 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
361 | local_irq_restore(flags); | |
362 | } | |
363 | ||
364 | EXPORT_SYMBOL(__tasklet_schedule); | |
365 | ||
7ad5b3a5 | 366 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
1da177e4 LT |
367 | { |
368 | unsigned long flags; | |
369 | ||
370 | local_irq_save(flags); | |
48f20a9a OJ |
371 | t->next = NULL; |
372 | *__get_cpu_var(tasklet_hi_vec).tail = t; | |
373 | __get_cpu_var(tasklet_hi_vec).tail = &(t->next); | |
1da177e4 LT |
374 | raise_softirq_irqoff(HI_SOFTIRQ); |
375 | local_irq_restore(flags); | |
376 | } | |
377 | ||
378 | EXPORT_SYMBOL(__tasklet_hi_schedule); | |
379 | ||
380 | static void tasklet_action(struct softirq_action *a) | |
381 | { | |
382 | struct tasklet_struct *list; | |
383 | ||
384 | local_irq_disable(); | |
48f20a9a OJ |
385 | list = __get_cpu_var(tasklet_vec).head; |
386 | __get_cpu_var(tasklet_vec).head = NULL; | |
387 | __get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head; | |
1da177e4 LT |
388 | local_irq_enable(); |
389 | ||
390 | while (list) { | |
391 | struct tasklet_struct *t = list; | |
392 | ||
393 | list = list->next; | |
394 | ||
395 | if (tasklet_trylock(t)) { | |
396 | if (!atomic_read(&t->count)) { | |
397 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) | |
398 | BUG(); | |
399 | t->func(t->data); | |
400 | tasklet_unlock(t); | |
401 | continue; | |
402 | } | |
403 | tasklet_unlock(t); | |
404 | } | |
405 | ||
406 | local_irq_disable(); | |
48f20a9a OJ |
407 | t->next = NULL; |
408 | *__get_cpu_var(tasklet_vec).tail = t; | |
409 | __get_cpu_var(tasklet_vec).tail = &(t->next); | |
1da177e4 LT |
410 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
411 | local_irq_enable(); | |
412 | } | |
413 | } | |
414 | ||
415 | static void tasklet_hi_action(struct softirq_action *a) | |
416 | { | |
417 | struct tasklet_struct *list; | |
418 | ||
419 | local_irq_disable(); | |
48f20a9a OJ |
420 | list = __get_cpu_var(tasklet_hi_vec).head; |
421 | __get_cpu_var(tasklet_hi_vec).head = NULL; | |
422 | __get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head; | |
1da177e4 LT |
423 | local_irq_enable(); |
424 | ||
425 | while (list) { | |
426 | struct tasklet_struct *t = list; | |
427 | ||
428 | list = list->next; | |
429 | ||
430 | if (tasklet_trylock(t)) { | |
431 | if (!atomic_read(&t->count)) { | |
432 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) | |
433 | BUG(); | |
434 | t->func(t->data); | |
435 | tasklet_unlock(t); | |
436 | continue; | |
437 | } | |
438 | tasklet_unlock(t); | |
439 | } | |
440 | ||
441 | local_irq_disable(); | |
48f20a9a OJ |
442 | t->next = NULL; |
443 | *__get_cpu_var(tasklet_hi_vec).tail = t; | |
444 | __get_cpu_var(tasklet_hi_vec).tail = &(t->next); | |
1da177e4 LT |
445 | __raise_softirq_irqoff(HI_SOFTIRQ); |
446 | local_irq_enable(); | |
447 | } | |
448 | } | |
449 | ||
450 | ||
451 | void tasklet_init(struct tasklet_struct *t, | |
452 | void (*func)(unsigned long), unsigned long data) | |
453 | { | |
454 | t->next = NULL; | |
455 | t->state = 0; | |
456 | atomic_set(&t->count, 0); | |
457 | t->func = func; | |
458 | t->data = data; | |
459 | } | |
460 | ||
461 | EXPORT_SYMBOL(tasklet_init); | |
462 | ||
463 | void tasklet_kill(struct tasklet_struct *t) | |
464 | { | |
465 | if (in_interrupt()) | |
466 | printk("Attempt to kill tasklet from interrupt\n"); | |
467 | ||
468 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { | |
469 | do | |
470 | yield(); | |
471 | while (test_bit(TASKLET_STATE_SCHED, &t->state)); | |
472 | } | |
473 | tasklet_unlock_wait(t); | |
474 | clear_bit(TASKLET_STATE_SCHED, &t->state); | |
475 | } | |
476 | ||
477 | EXPORT_SYMBOL(tasklet_kill); | |
478 | ||
54514a70 DM |
479 | DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); |
480 | EXPORT_PER_CPU_SYMBOL(softirq_work_list); | |
481 | ||
482 | static void __local_trigger(struct call_single_data *cp, int softirq) | |
483 | { | |
484 | struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]); | |
485 | ||
486 | list_add_tail(&cp->list, head); | |
487 | ||
488 | /* Trigger the softirq only if the list was previously empty. */ | |
489 | if (head->next == &cp->list) | |
490 | raise_softirq_irqoff(softirq); | |
491 | } | |
492 | ||
493 | #ifdef CONFIG_USE_GENERIC_SMP_HELPERS | |
494 | static void remote_softirq_receive(void *data) | |
495 | { | |
496 | struct call_single_data *cp = data; | |
497 | unsigned long flags; | |
498 | int softirq; | |
499 | ||
500 | softirq = cp->priv; | |
501 | ||
502 | local_irq_save(flags); | |
503 | __local_trigger(cp, softirq); | |
504 | local_irq_restore(flags); | |
505 | } | |
506 | ||
507 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
508 | { | |
509 | if (cpu_online(cpu)) { | |
510 | cp->func = remote_softirq_receive; | |
511 | cp->info = cp; | |
512 | cp->flags = 0; | |
513 | cp->priv = softirq; | |
514 | ||
515 | __smp_call_function_single(cpu, cp); | |
516 | return 0; | |
517 | } | |
518 | return 1; | |
519 | } | |
520 | #else /* CONFIG_USE_GENERIC_SMP_HELPERS */ | |
521 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
522 | { | |
523 | return 1; | |
524 | } | |
525 | #endif | |
526 | ||
527 | /** | |
528 | * __send_remote_softirq - try to schedule softirq work on a remote cpu | |
529 | * @cp: private SMP call function data area | |
530 | * @cpu: the remote cpu | |
531 | * @this_cpu: the currently executing cpu | |
532 | * @softirq: the softirq for the work | |
533 | * | |
534 | * Attempt to schedule softirq work on a remote cpu. If this cannot be | |
535 | * done, the work is instead queued up on the local cpu. | |
536 | * | |
537 | * Interrupts must be disabled. | |
538 | */ | |
539 | void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq) | |
540 | { | |
541 | if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq)) | |
542 | __local_trigger(cp, softirq); | |
543 | } | |
544 | EXPORT_SYMBOL(__send_remote_softirq); | |
545 | ||
546 | /** | |
547 | * send_remote_softirq - try to schedule softirq work on a remote cpu | |
548 | * @cp: private SMP call function data area | |
549 | * @cpu: the remote cpu | |
550 | * @softirq: the softirq for the work | |
551 | * | |
552 | * Like __send_remote_softirq except that disabling interrupts and | |
553 | * computing the current cpu is done for the caller. | |
554 | */ | |
555 | void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
556 | { | |
557 | unsigned long flags; | |
558 | int this_cpu; | |
559 | ||
560 | local_irq_save(flags); | |
561 | this_cpu = smp_processor_id(); | |
562 | __send_remote_softirq(cp, cpu, this_cpu, softirq); | |
563 | local_irq_restore(flags); | |
564 | } | |
565 | EXPORT_SYMBOL(send_remote_softirq); | |
566 | ||
567 | static int __cpuinit remote_softirq_cpu_notify(struct notifier_block *self, | |
568 | unsigned long action, void *hcpu) | |
569 | { | |
570 | /* | |
571 | * If a CPU goes away, splice its entries to the current CPU | |
572 | * and trigger a run of the softirq | |
573 | */ | |
574 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { | |
575 | int cpu = (unsigned long) hcpu; | |
576 | int i; | |
577 | ||
578 | local_irq_disable(); | |
579 | for (i = 0; i < NR_SOFTIRQS; i++) { | |
580 | struct list_head *head = &per_cpu(softirq_work_list[i], cpu); | |
581 | struct list_head *local_head; | |
582 | ||
583 | if (list_empty(head)) | |
584 | continue; | |
585 | ||
586 | local_head = &__get_cpu_var(softirq_work_list[i]); | |
587 | list_splice_init(head, local_head); | |
588 | raise_softirq_irqoff(i); | |
589 | } | |
590 | local_irq_enable(); | |
591 | } | |
592 | ||
593 | return NOTIFY_OK; | |
594 | } | |
595 | ||
596 | static struct notifier_block __cpuinitdata remote_softirq_cpu_notifier = { | |
597 | .notifier_call = remote_softirq_cpu_notify, | |
598 | }; | |
599 | ||
1da177e4 LT |
600 | void __init softirq_init(void) |
601 | { | |
48f20a9a OJ |
602 | int cpu; |
603 | ||
604 | for_each_possible_cpu(cpu) { | |
54514a70 DM |
605 | int i; |
606 | ||
48f20a9a OJ |
607 | per_cpu(tasklet_vec, cpu).tail = |
608 | &per_cpu(tasklet_vec, cpu).head; | |
609 | per_cpu(tasklet_hi_vec, cpu).tail = | |
610 | &per_cpu(tasklet_hi_vec, cpu).head; | |
54514a70 DM |
611 | for (i = 0; i < NR_SOFTIRQS; i++) |
612 | INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu)); | |
48f20a9a OJ |
613 | } |
614 | ||
54514a70 DM |
615 | register_hotcpu_notifier(&remote_softirq_cpu_notifier); |
616 | ||
962cf36c CM |
617 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
618 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); | |
1da177e4 LT |
619 | } |
620 | ||
621 | static int ksoftirqd(void * __bind_cpu) | |
622 | { | |
1da177e4 LT |
623 | set_current_state(TASK_INTERRUPTIBLE); |
624 | ||
625 | while (!kthread_should_stop()) { | |
626 | preempt_disable(); | |
627 | if (!local_softirq_pending()) { | |
628 | preempt_enable_no_resched(); | |
629 | schedule(); | |
630 | preempt_disable(); | |
631 | } | |
632 | ||
633 | __set_current_state(TASK_RUNNING); | |
634 | ||
635 | while (local_softirq_pending()) { | |
636 | /* Preempt disable stops cpu going offline. | |
637 | If already offline, we'll be on wrong CPU: | |
638 | don't process */ | |
639 | if (cpu_is_offline((long)__bind_cpu)) | |
640 | goto wait_to_die; | |
641 | do_softirq(); | |
642 | preempt_enable_no_resched(); | |
643 | cond_resched(); | |
644 | preempt_disable(); | |
645 | } | |
646 | preempt_enable(); | |
647 | set_current_state(TASK_INTERRUPTIBLE); | |
648 | } | |
649 | __set_current_state(TASK_RUNNING); | |
650 | return 0; | |
651 | ||
652 | wait_to_die: | |
653 | preempt_enable(); | |
654 | /* Wait for kthread_stop */ | |
655 | set_current_state(TASK_INTERRUPTIBLE); | |
656 | while (!kthread_should_stop()) { | |
657 | schedule(); | |
658 | set_current_state(TASK_INTERRUPTIBLE); | |
659 | } | |
660 | __set_current_state(TASK_RUNNING); | |
661 | return 0; | |
662 | } | |
663 | ||
664 | #ifdef CONFIG_HOTPLUG_CPU | |
665 | /* | |
666 | * tasklet_kill_immediate is called to remove a tasklet which can already be | |
667 | * scheduled for execution on @cpu. | |
668 | * | |
669 | * Unlike tasklet_kill, this function removes the tasklet | |
670 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. | |
671 | * | |
672 | * When this function is called, @cpu must be in the CPU_DEAD state. | |
673 | */ | |
674 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) | |
675 | { | |
676 | struct tasklet_struct **i; | |
677 | ||
678 | BUG_ON(cpu_online(cpu)); | |
679 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); | |
680 | ||
681 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) | |
682 | return; | |
683 | ||
684 | /* CPU is dead, so no lock needed. */ | |
48f20a9a | 685 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
1da177e4 LT |
686 | if (*i == t) { |
687 | *i = t->next; | |
48f20a9a OJ |
688 | /* If this was the tail element, move the tail ptr */ |
689 | if (*i == NULL) | |
690 | per_cpu(tasklet_vec, cpu).tail = i; | |
1da177e4 LT |
691 | return; |
692 | } | |
693 | } | |
694 | BUG(); | |
695 | } | |
696 | ||
697 | static void takeover_tasklets(unsigned int cpu) | |
698 | { | |
1da177e4 LT |
699 | /* CPU is dead, so no lock needed. */ |
700 | local_irq_disable(); | |
701 | ||
702 | /* Find end, append list for that CPU. */ | |
e5e41723 CB |
703 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
704 | *(__get_cpu_var(tasklet_vec).tail) = per_cpu(tasklet_vec, cpu).head; | |
705 | __get_cpu_var(tasklet_vec).tail = per_cpu(tasklet_vec, cpu).tail; | |
706 | per_cpu(tasklet_vec, cpu).head = NULL; | |
707 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; | |
708 | } | |
1da177e4 LT |
709 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
710 | ||
e5e41723 CB |
711 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
712 | *__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).head; | |
713 | __get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).tail; | |
714 | per_cpu(tasklet_hi_vec, cpu).head = NULL; | |
715 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; | |
716 | } | |
1da177e4 LT |
717 | raise_softirq_irqoff(HI_SOFTIRQ); |
718 | ||
719 | local_irq_enable(); | |
720 | } | |
721 | #endif /* CONFIG_HOTPLUG_CPU */ | |
722 | ||
8c78f307 | 723 | static int __cpuinit cpu_callback(struct notifier_block *nfb, |
1da177e4 LT |
724 | unsigned long action, |
725 | void *hcpu) | |
726 | { | |
727 | int hotcpu = (unsigned long)hcpu; | |
728 | struct task_struct *p; | |
729 | ||
730 | switch (action) { | |
731 | case CPU_UP_PREPARE: | |
8bb78442 | 732 | case CPU_UP_PREPARE_FROZEN: |
1da177e4 LT |
733 | p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu); |
734 | if (IS_ERR(p)) { | |
735 | printk("ksoftirqd for %i failed\n", hotcpu); | |
736 | return NOTIFY_BAD; | |
737 | } | |
738 | kthread_bind(p, hotcpu); | |
739 | per_cpu(ksoftirqd, hotcpu) = p; | |
740 | break; | |
741 | case CPU_ONLINE: | |
8bb78442 | 742 | case CPU_ONLINE_FROZEN: |
1da177e4 LT |
743 | wake_up_process(per_cpu(ksoftirqd, hotcpu)); |
744 | break; | |
745 | #ifdef CONFIG_HOTPLUG_CPU | |
746 | case CPU_UP_CANCELED: | |
8bb78442 | 747 | case CPU_UP_CANCELED_FROZEN: |
fc75cdfa HC |
748 | if (!per_cpu(ksoftirqd, hotcpu)) |
749 | break; | |
1da177e4 | 750 | /* Unbind so it can run. Fall thru. */ |
a4c4af7c HC |
751 | kthread_bind(per_cpu(ksoftirqd, hotcpu), |
752 | any_online_cpu(cpu_online_map)); | |
1da177e4 | 753 | case CPU_DEAD: |
1c6b4aa9 ST |
754 | case CPU_DEAD_FROZEN: { |
755 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; | |
756 | ||
1da177e4 LT |
757 | p = per_cpu(ksoftirqd, hotcpu); |
758 | per_cpu(ksoftirqd, hotcpu) = NULL; | |
961ccddd | 759 | sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); |
1da177e4 LT |
760 | kthread_stop(p); |
761 | takeover_tasklets(hotcpu); | |
762 | break; | |
1c6b4aa9 | 763 | } |
1da177e4 LT |
764 | #endif /* CONFIG_HOTPLUG_CPU */ |
765 | } | |
766 | return NOTIFY_OK; | |
767 | } | |
768 | ||
8c78f307 | 769 | static struct notifier_block __cpuinitdata cpu_nfb = { |
1da177e4 LT |
770 | .notifier_call = cpu_callback |
771 | }; | |
772 | ||
7babe8db | 773 | static __init int spawn_ksoftirqd(void) |
1da177e4 LT |
774 | { |
775 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 AM |
776 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
777 | ||
778 | BUG_ON(err == NOTIFY_BAD); | |
1da177e4 LT |
779 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
780 | register_cpu_notifier(&cpu_nfb); | |
781 | return 0; | |
782 | } | |
7babe8db | 783 | early_initcall(spawn_ksoftirqd); |
78eef01b AM |
784 | |
785 | #ifdef CONFIG_SMP | |
786 | /* | |
787 | * Call a function on all processors | |
788 | */ | |
15c8b6c1 | 789 | int on_each_cpu(void (*func) (void *info), void *info, int wait) |
78eef01b AM |
790 | { |
791 | int ret = 0; | |
792 | ||
793 | preempt_disable(); | |
8691e5a8 | 794 | ret = smp_call_function(func, info, wait); |
78eef01b AM |
795 | local_irq_disable(); |
796 | func(info); | |
797 | local_irq_enable(); | |
798 | preempt_enable(); | |
799 | return ret; | |
800 | } | |
801 | EXPORT_SYMBOL(on_each_cpu); | |
802 | #endif |