Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/kernel/softirq.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 11357 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | /* |
2 | * linux/kernel/softirq.c |
3 | * |
4 | * Copyright (C) 1992 Linus Torvalds |
5 | * |
6 | * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) |
7 | */ |
8 | |
9 | #include <linux/module.h> |
10 | #include <linux/kernel_stat.h> |
11 | #include <linux/interrupt.h> |
12 | #include <linux/init.h> |
13 | #include <linux/mm.h> |
14 | #include <linux/notifier.h> |
15 | #include <linux/percpu.h> |
16 | #include <linux/cpu.h> |
17 | #include <linux/kthread.h> |
18 | #include <linux/rcupdate.h> |
19 | |
20 | #include <asm/irq.h> |
21 | /* |
22 | - No shared variables, all the data are CPU local. |
23 | - If a softirq needs serialization, let it serialize itself |
24 | by its own spinlocks. |
25 | - Even if softirq is serialized, only local cpu is marked for |
26 | execution. Hence, we get something sort of weak cpu binding. |
27 | Though it is still not clear, will it result in better locality |
28 | or will not. |
29 | |
30 | Examples: |
31 | - NET RX softirq. It is multithreaded and does not require |
32 | any global serialization. |
33 | - NET TX softirq. It kicks software netdevice queues, hence |
34 | it is logically serialized per device, but this serialization |
35 | is invisible to common code. |
36 | - Tasklets: serialized wrt itself. |
37 | */ |
38 | |
39 | #ifndef __ARCH_IRQ_STAT |
40 | irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned; |
41 | EXPORT_SYMBOL(irq_stat); |
42 | #endif |
43 | |
44 | static struct softirq_action softirq_vec[32] __cacheline_aligned_in_smp; |
45 | |
46 | static DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
47 | |
48 | /* |
49 | * we cannot loop indefinitely here to avoid userspace starvation, |
50 | * but we also don't want to introduce a worst case 1/HZ latency |
51 | * to the pending events, so lets the scheduler to balance |
52 | * the softirq load for us. |
53 | */ |
54 | static inline void wakeup_softirqd(void) |
55 | { |
56 | /* Interrupts are disabled: no need to stop preemption */ |
57 | struct task_struct *tsk = __get_cpu_var(ksoftirqd); |
58 | |
59 | if (tsk && tsk->state != TASK_RUNNING) |
60 | wake_up_process(tsk); |
61 | } |
62 | |
63 | /* |
64 | * We restart softirq processing MAX_SOFTIRQ_RESTART times, |
65 | * and we fall back to softirqd after that. |
66 | * |
67 | * This number has been established via experimentation. |
68 | * The two things to balance is latency against fairness - |
69 | * we want to handle softirqs as soon as possible, but they |
70 | * should not be able to lock up the box. |
71 | */ |
72 | #define MAX_SOFTIRQ_RESTART 10 |
73 | |
74 | asmlinkage void __do_softirq(void) |
75 | { |
76 | struct softirq_action *h; |
77 | __u32 pending; |
78 | int max_restart = MAX_SOFTIRQ_RESTART; |
79 | int cpu; |
80 | |
81 | pending = local_softirq_pending(); |
82 | |
83 | local_bh_disable(); |
84 | cpu = smp_processor_id(); |
85 | restart: |
86 | /* Reset the pending bitmask before enabling irqs */ |
87 | local_softirq_pending() = 0; |
88 | |
89 | local_irq_enable(); |
90 | |
91 | h = softirq_vec; |
92 | |
93 | do { |
94 | if (pending & 1) { |
95 | h->action(h); |
96 | rcu_bh_qsctr_inc(cpu); |
97 | } |
98 | h++; |
99 | pending >>= 1; |
100 | } while (pending); |
101 | |
102 | local_irq_disable(); |
103 | |
104 | pending = local_softirq_pending(); |
105 | if (pending && --max_restart) |
106 | goto restart; |
107 | |
108 | if (pending) |
109 | wakeup_softirqd(); |
110 | |
111 | __local_bh_enable(); |
112 | } |
113 | |
114 | #ifndef __ARCH_HAS_DO_SOFTIRQ |
115 | |
116 | asmlinkage void do_softirq(void) |
117 | { |
118 | __u32 pending; |
119 | unsigned long flags; |
120 | |
121 | if (in_interrupt()) |
122 | return; |
123 | |
124 | local_irq_save(flags); |
125 | |
126 | pending = local_softirq_pending(); |
127 | |
128 | if (pending) |
129 | __do_softirq(); |
130 | |
131 | local_irq_restore(flags); |
132 | } |
133 | |
134 | EXPORT_SYMBOL(do_softirq); |
135 | |
136 | #endif |
137 | |
138 | void local_bh_enable(void) |
139 | { |
140 | WARN_ON(irqs_disabled()); |
141 | /* |
142 | * Keep preemption disabled until we are done with |
143 | * softirq processing: |
144 | */ |
145 | sub_preempt_count(SOFTIRQ_OFFSET - 1); |
146 | |
147 | if (unlikely(!in_interrupt() && local_softirq_pending())) |
148 | do_softirq(); |
149 | |
150 | dec_preempt_count(); |
151 | preempt_check_resched(); |
152 | } |
153 | EXPORT_SYMBOL(local_bh_enable); |
154 | |
155 | #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED |
156 | # define invoke_softirq() __do_softirq() |
157 | #else |
158 | # define invoke_softirq() do_softirq() |
159 | #endif |
160 | |
161 | /* |
162 | * Exit an interrupt context. Process softirqs if needed and possible: |
163 | */ |
164 | void irq_exit(void) |
165 | { |
166 | account_system_vtime(current); |
167 | sub_preempt_count(IRQ_EXIT_OFFSET); |
168 | if (!in_interrupt() && local_softirq_pending()) |
169 | invoke_softirq(); |
170 | preempt_enable_no_resched(); |
171 | } |
172 | |
173 | /* |
174 | * This function must run with irqs disabled! |
175 | */ |
176 | inline fastcall void raise_softirq_irqoff(unsigned int nr) |
177 | { |
178 | __raise_softirq_irqoff(nr); |
179 | |
180 | /* |
181 | * If we're in an interrupt or softirq, we're done |
182 | * (this also catches softirq-disabled code). We will |
183 | * actually run the softirq once we return from |
184 | * the irq or softirq. |
185 | * |
186 | * Otherwise we wake up ksoftirqd to make sure we |
187 | * schedule the softirq soon. |
188 | */ |
189 | if (!in_interrupt()) |
190 | wakeup_softirqd(); |
191 | } |
192 | |
193 | EXPORT_SYMBOL(raise_softirq_irqoff); |
194 | |
195 | void fastcall raise_softirq(unsigned int nr) |
196 | { |
197 | unsigned long flags; |
198 | |
199 | local_irq_save(flags); |
200 | raise_softirq_irqoff(nr); |
201 | local_irq_restore(flags); |
202 | } |
203 | |
204 | void open_softirq(int nr, void (*action)(struct softirq_action*), void *data) |
205 | { |
206 | softirq_vec[nr].data = data; |
207 | softirq_vec[nr].action = action; |
208 | } |
209 | |
210 | EXPORT_SYMBOL(open_softirq); |
211 | |
212 | /* Tasklets */ |
213 | struct tasklet_head |
214 | { |
215 | struct tasklet_struct *list; |
216 | }; |
217 | |
218 | /* Some compilers disobey section attribute on statics when not |
219 | initialized -- RR */ |
220 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL }; |
221 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL }; |
222 | |
223 | void fastcall __tasklet_schedule(struct tasklet_struct *t) |
224 | { |
225 | unsigned long flags; |
226 | |
227 | local_irq_save(flags); |
228 | t->next = __get_cpu_var(tasklet_vec).list; |
229 | __get_cpu_var(tasklet_vec).list = t; |
230 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
231 | local_irq_restore(flags); |
232 | } |
233 | |
234 | EXPORT_SYMBOL(__tasklet_schedule); |
235 | |
236 | void fastcall __tasklet_hi_schedule(struct tasklet_struct *t) |
237 | { |
238 | unsigned long flags; |
239 | |
240 | local_irq_save(flags); |
241 | t->next = __get_cpu_var(tasklet_hi_vec).list; |
242 | __get_cpu_var(tasklet_hi_vec).list = t; |
243 | raise_softirq_irqoff(HI_SOFTIRQ); |
244 | local_irq_restore(flags); |
245 | } |
246 | |
247 | EXPORT_SYMBOL(__tasklet_hi_schedule); |
248 | |
249 | static void tasklet_action(struct softirq_action *a) |
250 | { |
251 | struct tasklet_struct *list; |
252 | |
253 | local_irq_disable(); |
254 | list = __get_cpu_var(tasklet_vec).list; |
255 | __get_cpu_var(tasklet_vec).list = NULL; |
256 | local_irq_enable(); |
257 | |
258 | while (list) { |
259 | struct tasklet_struct *t = list; |
260 | |
261 | list = list->next; |
262 | |
263 | if (tasklet_trylock(t)) { |
264 | if (!atomic_read(&t->count)) { |
265 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
266 | BUG(); |
267 | t->func(t->data); |
268 | tasklet_unlock(t); |
269 | continue; |
270 | } |
271 | tasklet_unlock(t); |
272 | } |
273 | |
274 | local_irq_disable(); |
275 | t->next = __get_cpu_var(tasklet_vec).list; |
276 | __get_cpu_var(tasklet_vec).list = t; |
277 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
278 | local_irq_enable(); |
279 | } |
280 | } |
281 | |
282 | static void tasklet_hi_action(struct softirq_action *a) |
283 | { |
284 | struct tasklet_struct *list; |
285 | |
286 | local_irq_disable(); |
287 | list = __get_cpu_var(tasklet_hi_vec).list; |
288 | __get_cpu_var(tasklet_hi_vec).list = NULL; |
289 | local_irq_enable(); |
290 | |
291 | while (list) { |
292 | struct tasklet_struct *t = list; |
293 | |
294 | list = list->next; |
295 | |
296 | if (tasklet_trylock(t)) { |
297 | if (!atomic_read(&t->count)) { |
298 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
299 | BUG(); |
300 | t->func(t->data); |
301 | tasklet_unlock(t); |
302 | continue; |
303 | } |
304 | tasklet_unlock(t); |
305 | } |
306 | |
307 | local_irq_disable(); |
308 | t->next = __get_cpu_var(tasklet_hi_vec).list; |
309 | __get_cpu_var(tasklet_hi_vec).list = t; |
310 | __raise_softirq_irqoff(HI_SOFTIRQ); |
311 | local_irq_enable(); |
312 | } |
313 | } |
314 | |
315 | |
316 | void tasklet_init(struct tasklet_struct *t, |
317 | void (*func)(unsigned long), unsigned long data) |
318 | { |
319 | t->next = NULL; |
320 | t->state = 0; |
321 | atomic_set(&t->count, 0); |
322 | t->func = func; |
323 | t->data = data; |
324 | } |
325 | |
326 | EXPORT_SYMBOL(tasklet_init); |
327 | |
328 | void tasklet_kill(struct tasklet_struct *t) |
329 | { |
330 | if (in_interrupt()) |
331 | printk("Attempt to kill tasklet from interrupt\n"); |
332 | |
333 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { |
334 | do |
335 | yield(); |
336 | while (test_bit(TASKLET_STATE_SCHED, &t->state)); |
337 | } |
338 | tasklet_unlock_wait(t); |
339 | clear_bit(TASKLET_STATE_SCHED, &t->state); |
340 | } |
341 | |
342 | EXPORT_SYMBOL(tasklet_kill); |
343 | |
344 | void __init softirq_init(void) |
345 | { |
346 | open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL); |
347 | open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL); |
348 | } |
349 | |
350 | static int ksoftirqd(void * __bind_cpu) |
351 | { |
352 | set_user_nice(current, 19); |
353 | current->flags |= PF_NOFREEZE; |
354 | |
355 | set_current_state(TASK_INTERRUPTIBLE); |
356 | |
357 | while (!kthread_should_stop()) { |
358 | preempt_disable(); |
359 | if (!local_softirq_pending()) { |
360 | preempt_enable_no_resched(); |
361 | schedule(); |
362 | preempt_disable(); |
363 | } |
364 | |
365 | __set_current_state(TASK_RUNNING); |
366 | |
367 | while (local_softirq_pending()) { |
368 | /* Preempt disable stops cpu going offline. |
369 | If already offline, we'll be on wrong CPU: |
370 | don't process */ |
371 | if (cpu_is_offline((long)__bind_cpu)) |
372 | goto wait_to_die; |
373 | do_softirq(); |
374 | preempt_enable_no_resched(); |
375 | cond_resched(); |
376 | preempt_disable(); |
377 | } |
378 | preempt_enable(); |
379 | set_current_state(TASK_INTERRUPTIBLE); |
380 | } |
381 | __set_current_state(TASK_RUNNING); |
382 | return 0; |
383 | |
384 | wait_to_die: |
385 | preempt_enable(); |
386 | /* Wait for kthread_stop */ |
387 | set_current_state(TASK_INTERRUPTIBLE); |
388 | while (!kthread_should_stop()) { |
389 | schedule(); |
390 | set_current_state(TASK_INTERRUPTIBLE); |
391 | } |
392 | __set_current_state(TASK_RUNNING); |
393 | return 0; |
394 | } |
395 | |
396 | #ifdef CONFIG_HOTPLUG_CPU |
397 | /* |
398 | * tasklet_kill_immediate is called to remove a tasklet which can already be |
399 | * scheduled for execution on @cpu. |
400 | * |
401 | * Unlike tasklet_kill, this function removes the tasklet |
402 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. |
403 | * |
404 | * When this function is called, @cpu must be in the CPU_DEAD state. |
405 | */ |
406 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) |
407 | { |
408 | struct tasklet_struct **i; |
409 | |
410 | BUG_ON(cpu_online(cpu)); |
411 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); |
412 | |
413 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) |
414 | return; |
415 | |
416 | /* CPU is dead, so no lock needed. */ |
417 | for (i = &per_cpu(tasklet_vec, cpu).list; *i; i = &(*i)->next) { |
418 | if (*i == t) { |
419 | *i = t->next; |
420 | return; |
421 | } |
422 | } |
423 | BUG(); |
424 | } |
425 | |
426 | static void takeover_tasklets(unsigned int cpu) |
427 | { |
428 | struct tasklet_struct **i; |
429 | |
430 | /* CPU is dead, so no lock needed. */ |
431 | local_irq_disable(); |
432 | |
433 | /* Find end, append list for that CPU. */ |
434 | for (i = &__get_cpu_var(tasklet_vec).list; *i; i = &(*i)->next); |
435 | *i = per_cpu(tasklet_vec, cpu).list; |
436 | per_cpu(tasklet_vec, cpu).list = NULL; |
437 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
438 | |
439 | for (i = &__get_cpu_var(tasklet_hi_vec).list; *i; i = &(*i)->next); |
440 | *i = per_cpu(tasklet_hi_vec, cpu).list; |
441 | per_cpu(tasklet_hi_vec, cpu).list = NULL; |
442 | raise_softirq_irqoff(HI_SOFTIRQ); |
443 | |
444 | local_irq_enable(); |
445 | } |
446 | #endif /* CONFIG_HOTPLUG_CPU */ |
447 | |
448 | static int __devinit cpu_callback(struct notifier_block *nfb, |
449 | unsigned long action, |
450 | void *hcpu) |
451 | { |
452 | int hotcpu = (unsigned long)hcpu; |
453 | struct task_struct *p; |
454 | |
455 | switch (action) { |
456 | case CPU_UP_PREPARE: |
457 | BUG_ON(per_cpu(tasklet_vec, hotcpu).list); |
458 | BUG_ON(per_cpu(tasklet_hi_vec, hotcpu).list); |
459 | p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu); |
460 | if (IS_ERR(p)) { |
461 | printk("ksoftirqd for %i failed\n", hotcpu); |
462 | return NOTIFY_BAD; |
463 | } |
464 | kthread_bind(p, hotcpu); |
465 | per_cpu(ksoftirqd, hotcpu) = p; |
466 | break; |
467 | case CPU_ONLINE: |
468 | wake_up_process(per_cpu(ksoftirqd, hotcpu)); |
469 | break; |
470 | #ifdef CONFIG_HOTPLUG_CPU |
471 | case CPU_UP_CANCELED: |
472 | /* Unbind so it can run. Fall thru. */ |
473 | kthread_bind(per_cpu(ksoftirqd, hotcpu), smp_processor_id()); |
474 | case CPU_DEAD: |
475 | p = per_cpu(ksoftirqd, hotcpu); |
476 | per_cpu(ksoftirqd, hotcpu) = NULL; |
477 | kthread_stop(p); |
478 | takeover_tasklets(hotcpu); |
479 | break; |
480 | #endif /* CONFIG_HOTPLUG_CPU */ |
481 | } |
482 | return NOTIFY_OK; |
483 | } |
484 | |
485 | static struct notifier_block __devinitdata cpu_nfb = { |
486 | .notifier_call = cpu_callback |
487 | }; |
488 | |
489 | __init int spawn_ksoftirqd(void) |
490 | { |
491 | void *cpu = (void *)(long)smp_processor_id(); |
492 | cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
493 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
494 | register_cpu_notifier(&cpu_nfb); |
495 | return 0; |
496 | } |