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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 | |
11 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
12 | |
13 | #include <linux/export.h> |
14 | #include <linux/kernel_stat.h> |
15 | #include <linux/interrupt.h> |
16 | #include <linux/init.h> |
17 | #include <linux/mm.h> |
18 | #include <linux/notifier.h> |
19 | #include <linux/percpu.h> |
20 | #include <linux/cpu.h> |
21 | #include <linux/freezer.h> |
22 | #include <linux/kthread.h> |
23 | #include <linux/rcupdate.h> |
24 | #include <linux/ftrace.h> |
25 | #include <linux/smp.h> |
26 | #include <linux/smpboot.h> |
27 | #include <linux/tick.h> |
28 | #include <linux/irq.h> |
29 | |
30 | #define CREATE_TRACE_POINTS |
31 | #include <trace/events/irq.h> |
32 | |
33 | /* |
34 | - No shared variables, all the data are CPU local. |
35 | - If a softirq needs serialization, let it serialize itself |
36 | by its own spinlocks. |
37 | - Even if softirq is serialized, only local cpu is marked for |
38 | execution. Hence, we get something sort of weak cpu binding. |
39 | Though it is still not clear, will it result in better locality |
40 | or will not. |
41 | |
42 | Examples: |
43 | - NET RX softirq. It is multithreaded and does not require |
44 | any global serialization. |
45 | - NET TX softirq. It kicks software netdevice queues, hence |
46 | it is logically serialized per device, but this serialization |
47 | is invisible to common code. |
48 | - Tasklets: serialized wrt itself. |
49 | */ |
50 | |
51 | #ifndef __ARCH_IRQ_STAT |
52 | irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned; |
53 | EXPORT_SYMBOL(irq_stat); |
54 | #endif |
55 | |
56 | static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
57 | |
58 | DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
59 | |
60 | const char * const softirq_to_name[NR_SOFTIRQS] = { |
61 | "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL", |
62 | "TASKLET", "SCHED", "HRTIMER", "RCU" |
63 | }; |
64 | |
65 | /* |
66 | * we cannot loop indefinitely here to avoid userspace starvation, |
67 | * but we also don't want to introduce a worst case 1/HZ latency |
68 | * to the pending events, so lets the scheduler to balance |
69 | * the softirq load for us. |
70 | */ |
71 | static void wakeup_softirqd(void) |
72 | { |
73 | /* Interrupts are disabled: no need to stop preemption */ |
74 | struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
75 | |
76 | if (tsk && tsk->state != TASK_RUNNING) |
77 | wake_up_process(tsk); |
78 | } |
79 | |
80 | /* |
81 | * preempt_count and SOFTIRQ_OFFSET usage: |
82 | * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving |
83 | * softirq processing. |
84 | * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) |
85 | * on local_bh_disable or local_bh_enable. |
86 | * This lets us distinguish between whether we are currently processing |
87 | * softirq and whether we just have bh disabled. |
88 | */ |
89 | |
90 | /* |
91 | * This one is for softirq.c-internal use, |
92 | * where hardirqs are disabled legitimately: |
93 | */ |
94 | #ifdef CONFIG_TRACE_IRQFLAGS |
95 | void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) |
96 | { |
97 | unsigned long flags; |
98 | |
99 | WARN_ON_ONCE(in_irq()); |
100 | |
101 | raw_local_irq_save(flags); |
102 | /* |
103 | * The preempt tracer hooks into preempt_count_add and will break |
104 | * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET |
105 | * is set and before current->softirq_enabled is cleared. |
106 | * We must manually increment preempt_count here and manually |
107 | * call the trace_preempt_off later. |
108 | */ |
109 | __preempt_count_add(cnt); |
110 | /* |
111 | * Were softirqs turned off above: |
112 | */ |
113 | if (softirq_count() == (cnt & SOFTIRQ_MASK)) |
114 | trace_softirqs_off(ip); |
115 | raw_local_irq_restore(flags); |
116 | |
117 | if (preempt_count() == cnt) |
118 | trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); |
119 | } |
120 | EXPORT_SYMBOL(__local_bh_disable_ip); |
121 | #endif /* CONFIG_TRACE_IRQFLAGS */ |
122 | |
123 | static void __local_bh_enable(unsigned int cnt) |
124 | { |
125 | WARN_ON_ONCE(!irqs_disabled()); |
126 | |
127 | if (softirq_count() == (cnt & SOFTIRQ_MASK)) |
128 | trace_softirqs_on(_RET_IP_); |
129 | preempt_count_sub(cnt); |
130 | } |
131 | |
132 | /* |
133 | * Special-case - softirqs can safely be enabled in |
134 | * cond_resched_softirq(), or by __do_softirq(), |
135 | * without processing still-pending softirqs: |
136 | */ |
137 | void _local_bh_enable(void) |
138 | { |
139 | WARN_ON_ONCE(in_irq()); |
140 | __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); |
141 | } |
142 | EXPORT_SYMBOL(_local_bh_enable); |
143 | |
144 | void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) |
145 | { |
146 | WARN_ON_ONCE(in_irq() || irqs_disabled()); |
147 | #ifdef CONFIG_TRACE_IRQFLAGS |
148 | local_irq_disable(); |
149 | #endif |
150 | /* |
151 | * Are softirqs going to be turned on now: |
152 | */ |
153 | if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) |
154 | trace_softirqs_on(ip); |
155 | /* |
156 | * Keep preemption disabled until we are done with |
157 | * softirq processing: |
158 | */ |
159 | preempt_count_sub(cnt - 1); |
160 | |
161 | if (unlikely(!in_interrupt() && local_softirq_pending())) { |
162 | /* |
163 | * Run softirq if any pending. And do it in its own stack |
164 | * as we may be calling this deep in a task call stack already. |
165 | */ |
166 | do_softirq(); |
167 | } |
168 | |
169 | preempt_count_dec(); |
170 | #ifdef CONFIG_TRACE_IRQFLAGS |
171 | local_irq_enable(); |
172 | #endif |
173 | preempt_check_resched(); |
174 | } |
175 | EXPORT_SYMBOL(__local_bh_enable_ip); |
176 | |
177 | /* |
178 | * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, |
179 | * but break the loop if need_resched() is set or after 2 ms. |
180 | * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in |
181 | * certain cases, such as stop_machine(), jiffies may cease to |
182 | * increment and so we need the MAX_SOFTIRQ_RESTART limit as |
183 | * well to make sure we eventually return from this method. |
184 | * |
185 | * These limits have been established via experimentation. |
186 | * The two things to balance is latency against fairness - |
187 | * we want to handle softirqs as soon as possible, but they |
188 | * should not be able to lock up the box. |
189 | */ |
190 | #define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) |
191 | #define MAX_SOFTIRQ_RESTART 10 |
192 | |
193 | #ifdef CONFIG_TRACE_IRQFLAGS |
194 | /* |
195 | * When we run softirqs from irq_exit() and thus on the hardirq stack we need |
196 | * to keep the lockdep irq context tracking as tight as possible in order to |
197 | * not miss-qualify lock contexts and miss possible deadlocks. |
198 | */ |
199 | |
200 | static inline bool lockdep_softirq_start(void) |
201 | { |
202 | bool in_hardirq = false; |
203 | |
204 | if (trace_hardirq_context(current)) { |
205 | in_hardirq = true; |
206 | trace_hardirq_exit(); |
207 | } |
208 | |
209 | lockdep_softirq_enter(); |
210 | |
211 | return in_hardirq; |
212 | } |
213 | |
214 | static inline void lockdep_softirq_end(bool in_hardirq) |
215 | { |
216 | lockdep_softirq_exit(); |
217 | |
218 | if (in_hardirq) |
219 | trace_hardirq_enter(); |
220 | } |
221 | #else |
222 | static inline bool lockdep_softirq_start(void) { return false; } |
223 | static inline void lockdep_softirq_end(bool in_hardirq) { } |
224 | #endif |
225 | |
226 | asmlinkage __visible void __do_softirq(void) |
227 | { |
228 | unsigned long end = jiffies + MAX_SOFTIRQ_TIME; |
229 | unsigned long old_flags = current->flags; |
230 | int max_restart = MAX_SOFTIRQ_RESTART; |
231 | struct softirq_action *h; |
232 | bool in_hardirq; |
233 | __u32 pending; |
234 | int softirq_bit; |
235 | |
236 | /* |
237 | * Mask out PF_MEMALLOC s current task context is borrowed for the |
238 | * softirq. A softirq handled such as network RX might set PF_MEMALLOC |
239 | * again if the socket is related to swap |
240 | */ |
241 | current->flags &= ~PF_MEMALLOC; |
242 | |
243 | pending = local_softirq_pending(); |
244 | account_irq_enter_time(current); |
245 | |
246 | __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); |
247 | in_hardirq = lockdep_softirq_start(); |
248 | |
249 | restart: |
250 | /* Reset the pending bitmask before enabling irqs */ |
251 | set_softirq_pending(0); |
252 | |
253 | local_irq_enable(); |
254 | |
255 | h = softirq_vec; |
256 | |
257 | while ((softirq_bit = ffs(pending))) { |
258 | unsigned int vec_nr; |
259 | int prev_count; |
260 | |
261 | h += softirq_bit - 1; |
262 | |
263 | vec_nr = h - softirq_vec; |
264 | prev_count = preempt_count(); |
265 | |
266 | kstat_incr_softirqs_this_cpu(vec_nr); |
267 | |
268 | trace_softirq_entry(vec_nr); |
269 | h->action(h); |
270 | trace_softirq_exit(vec_nr); |
271 | if (unlikely(prev_count != preempt_count())) { |
272 | pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n", |
273 | vec_nr, softirq_to_name[vec_nr], h->action, |
274 | prev_count, preempt_count()); |
275 | preempt_count_set(prev_count); |
276 | } |
277 | h++; |
278 | pending >>= softirq_bit; |
279 | } |
280 | |
281 | rcu_bh_qs(smp_processor_id()); |
282 | local_irq_disable(); |
283 | |
284 | pending = local_softirq_pending(); |
285 | if (pending) { |
286 | if (time_before(jiffies, end) && !need_resched() && |
287 | --max_restart) |
288 | goto restart; |
289 | |
290 | wakeup_softirqd(); |
291 | } |
292 | |
293 | lockdep_softirq_end(in_hardirq); |
294 | account_irq_exit_time(current); |
295 | __local_bh_enable(SOFTIRQ_OFFSET); |
296 | WARN_ON_ONCE(in_interrupt()); |
297 | tsk_restore_flags(current, old_flags, PF_MEMALLOC); |
298 | } |
299 | |
300 | asmlinkage __visible void do_softirq(void) |
301 | { |
302 | __u32 pending; |
303 | unsigned long flags; |
304 | |
305 | if (in_interrupt()) |
306 | return; |
307 | |
308 | local_irq_save(flags); |
309 | |
310 | pending = local_softirq_pending(); |
311 | |
312 | if (pending) |
313 | do_softirq_own_stack(); |
314 | |
315 | local_irq_restore(flags); |
316 | } |
317 | |
318 | /* |
319 | * Enter an interrupt context. |
320 | */ |
321 | void irq_enter(void) |
322 | { |
323 | rcu_irq_enter(); |
324 | if (is_idle_task(current) && !in_interrupt()) { |
325 | /* |
326 | * Prevent raise_softirq from needlessly waking up ksoftirqd |
327 | * here, as softirq will be serviced on return from interrupt. |
328 | */ |
329 | local_bh_disable(); |
330 | tick_irq_enter(); |
331 | _local_bh_enable(); |
332 | } |
333 | |
334 | __irq_enter(); |
335 | } |
336 | |
337 | static inline void invoke_softirq(void) |
338 | { |
339 | if (!force_irqthreads) { |
340 | #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK |
341 | /* |
342 | * We can safely execute softirq on the current stack if |
343 | * it is the irq stack, because it should be near empty |
344 | * at this stage. |
345 | */ |
346 | __do_softirq(); |
347 | #else |
348 | /* |
349 | * Otherwise, irq_exit() is called on the task stack that can |
350 | * be potentially deep already. So call softirq in its own stack |
351 | * to prevent from any overrun. |
352 | */ |
353 | do_softirq_own_stack(); |
354 | #endif |
355 | } else { |
356 | wakeup_softirqd(); |
357 | } |
358 | } |
359 | |
360 | static inline void tick_irq_exit(void) |
361 | { |
362 | #ifdef CONFIG_NO_HZ_COMMON |
363 | int cpu = smp_processor_id(); |
364 | |
365 | /* Make sure that timer wheel updates are propagated */ |
366 | if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { |
367 | if (!in_interrupt()) |
368 | tick_nohz_irq_exit(); |
369 | } |
370 | #endif |
371 | } |
372 | |
373 | /* |
374 | * Exit an interrupt context. Process softirqs if needed and possible: |
375 | */ |
376 | void irq_exit(void) |
377 | { |
378 | #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED |
379 | local_irq_disable(); |
380 | #else |
381 | WARN_ON_ONCE(!irqs_disabled()); |
382 | #endif |
383 | |
384 | account_irq_exit_time(current); |
385 | preempt_count_sub(HARDIRQ_OFFSET); |
386 | if (!in_interrupt() && local_softirq_pending()) |
387 | invoke_softirq(); |
388 | |
389 | tick_irq_exit(); |
390 | rcu_irq_exit(); |
391 | trace_hardirq_exit(); /* must be last! */ |
392 | } |
393 | |
394 | /* |
395 | * This function must run with irqs disabled! |
396 | */ |
397 | inline void raise_softirq_irqoff(unsigned int nr) |
398 | { |
399 | __raise_softirq_irqoff(nr); |
400 | |
401 | /* |
402 | * If we're in an interrupt or softirq, we're done |
403 | * (this also catches softirq-disabled code). We will |
404 | * actually run the softirq once we return from |
405 | * the irq or softirq. |
406 | * |
407 | * Otherwise we wake up ksoftirqd to make sure we |
408 | * schedule the softirq soon. |
409 | */ |
410 | if (!in_interrupt()) |
411 | wakeup_softirqd(); |
412 | } |
413 | |
414 | void raise_softirq(unsigned int nr) |
415 | { |
416 | unsigned long flags; |
417 | |
418 | local_irq_save(flags); |
419 | raise_softirq_irqoff(nr); |
420 | local_irq_restore(flags); |
421 | } |
422 | |
423 | void __raise_softirq_irqoff(unsigned int nr) |
424 | { |
425 | trace_softirq_raise(nr); |
426 | or_softirq_pending(1UL << nr); |
427 | } |
428 | |
429 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
430 | { |
431 | softirq_vec[nr].action = action; |
432 | } |
433 | |
434 | /* |
435 | * Tasklets |
436 | */ |
437 | struct tasklet_head { |
438 | struct tasklet_struct *head; |
439 | struct tasklet_struct **tail; |
440 | }; |
441 | |
442 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
443 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); |
444 | |
445 | void __tasklet_schedule(struct tasklet_struct *t) |
446 | { |
447 | unsigned long flags; |
448 | |
449 | local_irq_save(flags); |
450 | t->next = NULL; |
451 | *__this_cpu_read(tasklet_vec.tail) = t; |
452 | __this_cpu_write(tasklet_vec.tail, &(t->next)); |
453 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
454 | local_irq_restore(flags); |
455 | } |
456 | EXPORT_SYMBOL(__tasklet_schedule); |
457 | |
458 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
459 | { |
460 | unsigned long flags; |
461 | |
462 | local_irq_save(flags); |
463 | t->next = NULL; |
464 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
465 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); |
466 | raise_softirq_irqoff(HI_SOFTIRQ); |
467 | local_irq_restore(flags); |
468 | } |
469 | EXPORT_SYMBOL(__tasklet_hi_schedule); |
470 | |
471 | void __tasklet_hi_schedule_first(struct tasklet_struct *t) |
472 | { |
473 | BUG_ON(!irqs_disabled()); |
474 | |
475 | t->next = __this_cpu_read(tasklet_hi_vec.head); |
476 | __this_cpu_write(tasklet_hi_vec.head, t); |
477 | __raise_softirq_irqoff(HI_SOFTIRQ); |
478 | } |
479 | EXPORT_SYMBOL(__tasklet_hi_schedule_first); |
480 | |
481 | static void tasklet_action(struct softirq_action *a) |
482 | { |
483 | struct tasklet_struct *list; |
484 | |
485 | local_irq_disable(); |
486 | list = __this_cpu_read(tasklet_vec.head); |
487 | __this_cpu_write(tasklet_vec.head, NULL); |
488 | __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head); |
489 | local_irq_enable(); |
490 | |
491 | while (list) { |
492 | struct tasklet_struct *t = list; |
493 | |
494 | list = list->next; |
495 | |
496 | if (tasklet_trylock(t)) { |
497 | if (!atomic_read(&t->count)) { |
498 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, |
499 | &t->state)) |
500 | BUG(); |
501 | t->func(t->data); |
502 | tasklet_unlock(t); |
503 | continue; |
504 | } |
505 | tasklet_unlock(t); |
506 | } |
507 | |
508 | local_irq_disable(); |
509 | t->next = NULL; |
510 | *__this_cpu_read(tasklet_vec.tail) = t; |
511 | __this_cpu_write(tasklet_vec.tail, &(t->next)); |
512 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
513 | local_irq_enable(); |
514 | } |
515 | } |
516 | |
517 | static void tasklet_hi_action(struct softirq_action *a) |
518 | { |
519 | struct tasklet_struct *list; |
520 | |
521 | local_irq_disable(); |
522 | list = __this_cpu_read(tasklet_hi_vec.head); |
523 | __this_cpu_write(tasklet_hi_vec.head, NULL); |
524 | __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head); |
525 | local_irq_enable(); |
526 | |
527 | while (list) { |
528 | struct tasklet_struct *t = list; |
529 | |
530 | list = list->next; |
531 | |
532 | if (tasklet_trylock(t)) { |
533 | if (!atomic_read(&t->count)) { |
534 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, |
535 | &t->state)) |
536 | BUG(); |
537 | t->func(t->data); |
538 | tasklet_unlock(t); |
539 | continue; |
540 | } |
541 | tasklet_unlock(t); |
542 | } |
543 | |
544 | local_irq_disable(); |
545 | t->next = NULL; |
546 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
547 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); |
548 | __raise_softirq_irqoff(HI_SOFTIRQ); |
549 | local_irq_enable(); |
550 | } |
551 | } |
552 | |
553 | void tasklet_init(struct tasklet_struct *t, |
554 | void (*func)(unsigned long), unsigned long data) |
555 | { |
556 | t->next = NULL; |
557 | t->state = 0; |
558 | atomic_set(&t->count, 0); |
559 | t->func = func; |
560 | t->data = data; |
561 | } |
562 | EXPORT_SYMBOL(tasklet_init); |
563 | |
564 | void tasklet_kill(struct tasklet_struct *t) |
565 | { |
566 | if (in_interrupt()) |
567 | pr_notice("Attempt to kill tasklet from interrupt\n"); |
568 | |
569 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { |
570 | do { |
571 | yield(); |
572 | } while (test_bit(TASKLET_STATE_SCHED, &t->state)); |
573 | } |
574 | tasklet_unlock_wait(t); |
575 | clear_bit(TASKLET_STATE_SCHED, &t->state); |
576 | } |
577 | EXPORT_SYMBOL(tasklet_kill); |
578 | |
579 | /* |
580 | * tasklet_hrtimer |
581 | */ |
582 | |
583 | /* |
584 | * The trampoline is called when the hrtimer expires. It schedules a tasklet |
585 | * to run __tasklet_hrtimer_trampoline() which in turn will call the intended |
586 | * hrtimer callback, but from softirq context. |
587 | */ |
588 | static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer) |
589 | { |
590 | struct tasklet_hrtimer *ttimer = |
591 | container_of(timer, struct tasklet_hrtimer, timer); |
592 | |
593 | tasklet_hi_schedule(&ttimer->tasklet); |
594 | return HRTIMER_NORESTART; |
595 | } |
596 | |
597 | /* |
598 | * Helper function which calls the hrtimer callback from |
599 | * tasklet/softirq context |
600 | */ |
601 | static void __tasklet_hrtimer_trampoline(unsigned long data) |
602 | { |
603 | struct tasklet_hrtimer *ttimer = (void *)data; |
604 | enum hrtimer_restart restart; |
605 | |
606 | restart = ttimer->function(&ttimer->timer); |
607 | if (restart != HRTIMER_NORESTART) |
608 | hrtimer_restart(&ttimer->timer); |
609 | } |
610 | |
611 | /** |
612 | * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks |
613 | * @ttimer: tasklet_hrtimer which is initialized |
614 | * @function: hrtimer callback function which gets called from softirq context |
615 | * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME) |
616 | * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL) |
617 | */ |
618 | void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer, |
619 | enum hrtimer_restart (*function)(struct hrtimer *), |
620 | clockid_t which_clock, enum hrtimer_mode mode) |
621 | { |
622 | hrtimer_init(&ttimer->timer, which_clock, mode); |
623 | ttimer->timer.function = __hrtimer_tasklet_trampoline; |
624 | tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline, |
625 | (unsigned long)ttimer); |
626 | ttimer->function = function; |
627 | } |
628 | EXPORT_SYMBOL_GPL(tasklet_hrtimer_init); |
629 | |
630 | void __init softirq_init(void) |
631 | { |
632 | int cpu; |
633 | |
634 | for_each_possible_cpu(cpu) { |
635 | per_cpu(tasklet_vec, cpu).tail = |
636 | &per_cpu(tasklet_vec, cpu).head; |
637 | per_cpu(tasklet_hi_vec, cpu).tail = |
638 | &per_cpu(tasklet_hi_vec, cpu).head; |
639 | } |
640 | |
641 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
642 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); |
643 | } |
644 | |
645 | static int ksoftirqd_should_run(unsigned int cpu) |
646 | { |
647 | return local_softirq_pending(); |
648 | } |
649 | |
650 | static void run_ksoftirqd(unsigned int cpu) |
651 | { |
652 | local_irq_disable(); |
653 | if (local_softirq_pending()) { |
654 | /* |
655 | * We can safely run softirq on inline stack, as we are not deep |
656 | * in the task stack here. |
657 | */ |
658 | __do_softirq(); |
659 | rcu_note_context_switch(cpu); |
660 | local_irq_enable(); |
661 | cond_resched(); |
662 | return; |
663 | } |
664 | local_irq_enable(); |
665 | } |
666 | |
667 | #ifdef CONFIG_HOTPLUG_CPU |
668 | /* |
669 | * tasklet_kill_immediate is called to remove a tasklet which can already be |
670 | * scheduled for execution on @cpu. |
671 | * |
672 | * Unlike tasklet_kill, this function removes the tasklet |
673 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. |
674 | * |
675 | * When this function is called, @cpu must be in the CPU_DEAD state. |
676 | */ |
677 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) |
678 | { |
679 | struct tasklet_struct **i; |
680 | |
681 | BUG_ON(cpu_online(cpu)); |
682 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); |
683 | |
684 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) |
685 | return; |
686 | |
687 | /* CPU is dead, so no lock needed. */ |
688 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
689 | if (*i == t) { |
690 | *i = t->next; |
691 | /* If this was the tail element, move the tail ptr */ |
692 | if (*i == NULL) |
693 | per_cpu(tasklet_vec, cpu).tail = i; |
694 | return; |
695 | } |
696 | } |
697 | BUG(); |
698 | } |
699 | |
700 | static void takeover_tasklets(unsigned int cpu) |
701 | { |
702 | /* CPU is dead, so no lock needed. */ |
703 | local_irq_disable(); |
704 | |
705 | /* Find end, append list for that CPU. */ |
706 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
707 | *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; |
708 | this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); |
709 | per_cpu(tasklet_vec, cpu).head = NULL; |
710 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; |
711 | } |
712 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
713 | |
714 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
715 | *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; |
716 | __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); |
717 | per_cpu(tasklet_hi_vec, cpu).head = NULL; |
718 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; |
719 | } |
720 | raise_softirq_irqoff(HI_SOFTIRQ); |
721 | |
722 | local_irq_enable(); |
723 | } |
724 | #endif /* CONFIG_HOTPLUG_CPU */ |
725 | |
726 | static int cpu_callback(struct notifier_block *nfb, unsigned long action, |
727 | void *hcpu) |
728 | { |
729 | switch (action) { |
730 | #ifdef CONFIG_HOTPLUG_CPU |
731 | case CPU_DEAD: |
732 | case CPU_DEAD_FROZEN: |
733 | takeover_tasklets((unsigned long)hcpu); |
734 | break; |
735 | #endif /* CONFIG_HOTPLUG_CPU */ |
736 | } |
737 | return NOTIFY_OK; |
738 | } |
739 | |
740 | static struct notifier_block cpu_nfb = { |
741 | .notifier_call = cpu_callback |
742 | }; |
743 | |
744 | static struct smp_hotplug_thread softirq_threads = { |
745 | .store = &ksoftirqd, |
746 | .thread_should_run = ksoftirqd_should_run, |
747 | .thread_fn = run_ksoftirqd, |
748 | .thread_comm = "ksoftirqd/%u", |
749 | }; |
750 | |
751 | static __init int spawn_ksoftirqd(void) |
752 | { |
753 | register_cpu_notifier(&cpu_nfb); |
754 | |
755 | BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); |
756 | |
757 | return 0; |
758 | } |
759 | early_initcall(spawn_ksoftirqd); |
760 | |
761 | /* |
762 | * [ These __weak aliases are kept in a separate compilation unit, so that |
763 | * GCC does not inline them incorrectly. ] |
764 | */ |
765 | |
766 | int __init __weak early_irq_init(void) |
767 | { |
768 | return 0; |
769 | } |
770 | |
771 | int __init __weak arch_probe_nr_irqs(void) |
772 | { |
773 | return NR_IRQS_LEGACY; |
774 | } |
775 | |
776 | int __init __weak arch_early_irq_init(void) |
777 | { |
778 | return 0; |
779 | } |
780 | |
781 | unsigned int __weak arch_dynirq_lower_bound(unsigned int from) |
782 | { |
783 | return from; |
784 | } |
785 |
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v2.6.34-rc5
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