Commit | Line | Data |
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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 | ||
9984de1a | 13 | #include <linux/export.h> |
1da177e4 LT |
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> | |
7e49fcce | 24 | #include <linux/ftrace.h> |
78eef01b | 25 | #include <linux/smp.h> |
3e339b5d | 26 | #include <linux/smpboot.h> |
79bf2bb3 | 27 | #include <linux/tick.h> |
a0e39ed3 HC |
28 | |
29 | #define CREATE_TRACE_POINTS | |
ad8d75ff | 30 | #include <trace/events/irq.h> |
1da177e4 LT |
31 | |
32 | #include <asm/irq.h> | |
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 | ||
978b0116 | 56 | static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
1da177e4 | 57 | |
4dd53d89 | 58 | DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
1da177e4 | 59 | |
5d592b44 | 60 | char *softirq_to_name[NR_SOFTIRQS] = { |
5dd4de58 | 61 | "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL", |
09223371 | 62 | "TASKLET", "SCHED", "HRTIMER", "RCU" |
5d592b44 JB |
63 | }; |
64 | ||
1da177e4 LT |
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 | */ | |
676cb02d | 71 | static void wakeup_softirqd(void) |
1da177e4 LT |
72 | { |
73 | /* Interrupts are disabled: no need to stop preemption */ | |
909ea964 | 74 | struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
1da177e4 LT |
75 | |
76 | if (tsk && tsk->state != TASK_RUNNING) | |
77 | wake_up_process(tsk); | |
78 | } | |
79 | ||
75e1056f VP |
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 | ||
de30a2b3 IM |
90 | /* |
91 | * This one is for softirq.c-internal use, | |
92 | * where hardirqs are disabled legitimately: | |
93 | */ | |
3c829c36 | 94 | #ifdef CONFIG_TRACE_IRQFLAGS |
75e1056f | 95 | static void __local_bh_disable(unsigned long ip, unsigned int cnt) |
de30a2b3 IM |
96 | { |
97 | unsigned long flags; | |
98 | ||
99 | WARN_ON_ONCE(in_irq()); | |
100 | ||
101 | raw_local_irq_save(flags); | |
7e49fcce SR |
102 | /* |
103 | * The preempt tracer hooks into add_preempt_count 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 | */ | |
75e1056f | 109 | preempt_count() += cnt; |
de30a2b3 IM |
110 | /* |
111 | * Were softirqs turned off above: | |
112 | */ | |
75e1056f | 113 | if (softirq_count() == cnt) |
de30a2b3 IM |
114 | trace_softirqs_off(ip); |
115 | raw_local_irq_restore(flags); | |
7e49fcce | 116 | |
75e1056f | 117 | if (preempt_count() == cnt) |
7e49fcce | 118 | trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); |
de30a2b3 | 119 | } |
3c829c36 | 120 | #else /* !CONFIG_TRACE_IRQFLAGS */ |
75e1056f | 121 | static inline void __local_bh_disable(unsigned long ip, unsigned int cnt) |
3c829c36 | 122 | { |
75e1056f | 123 | add_preempt_count(cnt); |
3c829c36 TC |
124 | barrier(); |
125 | } | |
126 | #endif /* CONFIG_TRACE_IRQFLAGS */ | |
de30a2b3 IM |
127 | |
128 | void local_bh_disable(void) | |
129 | { | |
d2e08473 | 130 | __local_bh_disable(_RET_IP_, SOFTIRQ_DISABLE_OFFSET); |
de30a2b3 IM |
131 | } |
132 | ||
133 | EXPORT_SYMBOL(local_bh_disable); | |
134 | ||
75e1056f VP |
135 | static void __local_bh_enable(unsigned int cnt) |
136 | { | |
137 | WARN_ON_ONCE(in_irq()); | |
138 | WARN_ON_ONCE(!irqs_disabled()); | |
139 | ||
140 | if (softirq_count() == cnt) | |
d2e08473 | 141 | trace_softirqs_on(_RET_IP_); |
75e1056f VP |
142 | sub_preempt_count(cnt); |
143 | } | |
144 | ||
de30a2b3 IM |
145 | /* |
146 | * Special-case - softirqs can safely be enabled in | |
147 | * cond_resched_softirq(), or by __do_softirq(), | |
148 | * without processing still-pending softirqs: | |
149 | */ | |
150 | void _local_bh_enable(void) | |
151 | { | |
75e1056f | 152 | __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); |
de30a2b3 IM |
153 | } |
154 | ||
155 | EXPORT_SYMBOL(_local_bh_enable); | |
156 | ||
0f476b6d | 157 | static inline void _local_bh_enable_ip(unsigned long ip) |
de30a2b3 | 158 | { |
0f476b6d | 159 | WARN_ON_ONCE(in_irq() || irqs_disabled()); |
3c829c36 | 160 | #ifdef CONFIG_TRACE_IRQFLAGS |
0f476b6d | 161 | local_irq_disable(); |
3c829c36 | 162 | #endif |
de30a2b3 IM |
163 | /* |
164 | * Are softirqs going to be turned on now: | |
165 | */ | |
75e1056f | 166 | if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) |
0f476b6d | 167 | trace_softirqs_on(ip); |
de30a2b3 IM |
168 | /* |
169 | * Keep preemption disabled until we are done with | |
170 | * softirq processing: | |
171 | */ | |
75e1056f | 172 | sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1); |
de30a2b3 IM |
173 | |
174 | if (unlikely(!in_interrupt() && local_softirq_pending())) | |
175 | do_softirq(); | |
176 | ||
177 | dec_preempt_count(); | |
3c829c36 | 178 | #ifdef CONFIG_TRACE_IRQFLAGS |
0f476b6d | 179 | local_irq_enable(); |
3c829c36 | 180 | #endif |
de30a2b3 IM |
181 | preempt_check_resched(); |
182 | } | |
0f476b6d JB |
183 | |
184 | void local_bh_enable(void) | |
185 | { | |
d2e08473 | 186 | _local_bh_enable_ip(_RET_IP_); |
0f476b6d | 187 | } |
de30a2b3 IM |
188 | EXPORT_SYMBOL(local_bh_enable); |
189 | ||
190 | void local_bh_enable_ip(unsigned long ip) | |
191 | { | |
0f476b6d | 192 | _local_bh_enable_ip(ip); |
de30a2b3 IM |
193 | } |
194 | EXPORT_SYMBOL(local_bh_enable_ip); | |
195 | ||
1da177e4 | 196 | /* |
34376a50 BG |
197 | * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, |
198 | * but break the loop if need_resched() is set or after 2 ms. | |
199 | * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in | |
200 | * certain cases, such as stop_machine(), jiffies may cease to | |
201 | * increment and so we need the MAX_SOFTIRQ_RESTART limit as | |
202 | * well to make sure we eventually return from this method. | |
1da177e4 | 203 | * |
c10d7367 | 204 | * These limits have been established via experimentation. |
1da177e4 LT |
205 | * The two things to balance is latency against fairness - |
206 | * we want to handle softirqs as soon as possible, but they | |
207 | * should not be able to lock up the box. | |
208 | */ | |
c10d7367 | 209 | #define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) |
34376a50 | 210 | #define MAX_SOFTIRQ_RESTART 10 |
1da177e4 LT |
211 | |
212 | asmlinkage void __do_softirq(void) | |
213 | { | |
214 | struct softirq_action *h; | |
215 | __u32 pending; | |
c10d7367 | 216 | unsigned long end = jiffies + MAX_SOFTIRQ_TIME; |
1da177e4 | 217 | int cpu; |
907aed48 | 218 | unsigned long old_flags = current->flags; |
34376a50 | 219 | int max_restart = MAX_SOFTIRQ_RESTART; |
907aed48 MG |
220 | |
221 | /* | |
222 | * Mask out PF_MEMALLOC s current task context is borrowed for the | |
223 | * softirq. A softirq handled such as network RX might set PF_MEMALLOC | |
224 | * again if the socket is related to swap | |
225 | */ | |
226 | current->flags &= ~PF_MEMALLOC; | |
1da177e4 LT |
227 | |
228 | pending = local_softirq_pending(); | |
6a61671b | 229 | account_irq_enter_time(current); |
829035fd | 230 | |
d2e08473 | 231 | __local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET); |
d820ac4c | 232 | lockdep_softirq_enter(); |
1da177e4 | 233 | |
1da177e4 LT |
234 | cpu = smp_processor_id(); |
235 | restart: | |
236 | /* Reset the pending bitmask before enabling irqs */ | |
3f74478b | 237 | set_softirq_pending(0); |
1da177e4 | 238 | |
c70f5d66 | 239 | local_irq_enable(); |
1da177e4 LT |
240 | |
241 | h = softirq_vec; | |
242 | ||
243 | do { | |
244 | if (pending & 1) { | |
f4bc6bb2 | 245 | unsigned int vec_nr = h - softirq_vec; |
8e85b4b5 TG |
246 | int prev_count = preempt_count(); |
247 | ||
f4bc6bb2 TG |
248 | kstat_incr_softirqs_this_cpu(vec_nr); |
249 | ||
250 | trace_softirq_entry(vec_nr); | |
1da177e4 | 251 | h->action(h); |
f4bc6bb2 | 252 | trace_softirq_exit(vec_nr); |
8e85b4b5 | 253 | if (unlikely(prev_count != preempt_count())) { |
f4bc6bb2 | 254 | printk(KERN_ERR "huh, entered softirq %u %s %p" |
8e85b4b5 | 255 | "with preempt_count %08x," |
f4bc6bb2 TG |
256 | " exited with %08x?\n", vec_nr, |
257 | softirq_to_name[vec_nr], h->action, | |
258 | prev_count, preempt_count()); | |
8e85b4b5 TG |
259 | preempt_count() = prev_count; |
260 | } | |
261 | ||
d6714c22 | 262 | rcu_bh_qs(cpu); |
1da177e4 LT |
263 | } |
264 | h++; | |
265 | pending >>= 1; | |
266 | } while (pending); | |
267 | ||
c70f5d66 | 268 | local_irq_disable(); |
1da177e4 LT |
269 | |
270 | pending = local_softirq_pending(); | |
c10d7367 | 271 | if (pending) { |
34376a50 BG |
272 | if (time_before(jiffies, end) && !need_resched() && |
273 | --max_restart) | |
c10d7367 | 274 | goto restart; |
1da177e4 | 275 | |
1da177e4 | 276 | wakeup_softirqd(); |
c10d7367 | 277 | } |
1da177e4 | 278 | |
d820ac4c | 279 | lockdep_softirq_exit(); |
829035fd | 280 | |
6a61671b | 281 | account_irq_exit_time(current); |
75e1056f | 282 | __local_bh_enable(SOFTIRQ_OFFSET); |
907aed48 | 283 | tsk_restore_flags(current, old_flags, PF_MEMALLOC); |
1da177e4 LT |
284 | } |
285 | ||
286 | #ifndef __ARCH_HAS_DO_SOFTIRQ | |
287 | ||
288 | asmlinkage void do_softirq(void) | |
289 | { | |
290 | __u32 pending; | |
291 | unsigned long flags; | |
292 | ||
293 | if (in_interrupt()) | |
294 | return; | |
295 | ||
296 | local_irq_save(flags); | |
297 | ||
298 | pending = local_softirq_pending(); | |
299 | ||
300 | if (pending) | |
301 | __do_softirq(); | |
302 | ||
303 | local_irq_restore(flags); | |
304 | } | |
305 | ||
1da177e4 LT |
306 | #endif |
307 | ||
dde4b2b5 IM |
308 | /* |
309 | * Enter an interrupt context. | |
310 | */ | |
311 | void irq_enter(void) | |
312 | { | |
6378ddb5 | 313 | int cpu = smp_processor_id(); |
719254fa | 314 | |
64db4cff | 315 | rcu_irq_enter(); |
0a8a2e78 | 316 | if (is_idle_task(current) && !in_interrupt()) { |
d267f87f VP |
317 | /* |
318 | * Prevent raise_softirq from needlessly waking up ksoftirqd | |
319 | * here, as softirq will be serviced on return from interrupt. | |
320 | */ | |
321 | local_bh_disable(); | |
719254fa | 322 | tick_check_idle(cpu); |
d267f87f VP |
323 | _local_bh_enable(); |
324 | } | |
325 | ||
326 | __irq_enter(); | |
dde4b2b5 IM |
327 | } |
328 | ||
8d32a307 TG |
329 | static inline void invoke_softirq(void) |
330 | { | |
ded79754 FW |
331 | if (!force_irqthreads) { |
332 | /* | |
333 | * We can safely execute softirq on the current stack if | |
334 | * it is the irq stack, because it should be near empty | |
335 | * at this stage. But we have no way to know if the arch | |
336 | * calls irq_exit() on the irq stack. So call softirq | |
337 | * in its own stack to prevent from any overrun on top | |
338 | * of a potentially deep task stack. | |
339 | */ | |
340 | do_softirq(); | |
341 | } else { | |
8d32a307 | 342 | wakeup_softirqd(); |
ded79754 | 343 | } |
8d32a307 | 344 | } |
1da177e4 | 345 | |
67826eae FW |
346 | static inline void tick_irq_exit(void) |
347 | { | |
348 | #ifdef CONFIG_NO_HZ_COMMON | |
349 | int cpu = smp_processor_id(); | |
350 | ||
351 | /* Make sure that timer wheel updates are propagated */ | |
352 | if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { | |
353 | if (!in_interrupt()) | |
354 | tick_nohz_irq_exit(); | |
355 | } | |
356 | #endif | |
357 | } | |
358 | ||
1da177e4 LT |
359 | /* |
360 | * Exit an interrupt context. Process softirqs if needed and possible: | |
361 | */ | |
362 | void irq_exit(void) | |
363 | { | |
74eed016 | 364 | #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED |
4cd5d111 | 365 | local_irq_disable(); |
74eed016 TG |
366 | #else |
367 | WARN_ON_ONCE(!irqs_disabled()); | |
368 | #endif | |
369 | ||
6a61671b | 370 | account_irq_exit_time(current); |
de30a2b3 | 371 | trace_hardirq_exit(); |
4d4c4e24 | 372 | sub_preempt_count(HARDIRQ_OFFSET); |
1da177e4 LT |
373 | if (!in_interrupt() && local_softirq_pending()) |
374 | invoke_softirq(); | |
79bf2bb3 | 375 | |
67826eae | 376 | tick_irq_exit(); |
416eb33c | 377 | rcu_irq_exit(); |
1da177e4 LT |
378 | } |
379 | ||
380 | /* | |
381 | * This function must run with irqs disabled! | |
382 | */ | |
7ad5b3a5 | 383 | inline void raise_softirq_irqoff(unsigned int nr) |
1da177e4 LT |
384 | { |
385 | __raise_softirq_irqoff(nr); | |
386 | ||
387 | /* | |
388 | * If we're in an interrupt or softirq, we're done | |
389 | * (this also catches softirq-disabled code). We will | |
390 | * actually run the softirq once we return from | |
391 | * the irq or softirq. | |
392 | * | |
393 | * Otherwise we wake up ksoftirqd to make sure we | |
394 | * schedule the softirq soon. | |
395 | */ | |
396 | if (!in_interrupt()) | |
397 | wakeup_softirqd(); | |
398 | } | |
399 | ||
7ad5b3a5 | 400 | void raise_softirq(unsigned int nr) |
1da177e4 LT |
401 | { |
402 | unsigned long flags; | |
403 | ||
404 | local_irq_save(flags); | |
405 | raise_softirq_irqoff(nr); | |
406 | local_irq_restore(flags); | |
407 | } | |
408 | ||
f069686e SR |
409 | void __raise_softirq_irqoff(unsigned int nr) |
410 | { | |
411 | trace_softirq_raise(nr); | |
412 | or_softirq_pending(1UL << nr); | |
413 | } | |
414 | ||
962cf36c | 415 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
1da177e4 | 416 | { |
1da177e4 LT |
417 | softirq_vec[nr].action = action; |
418 | } | |
419 | ||
9ba5f005 PZ |
420 | /* |
421 | * Tasklets | |
422 | */ | |
1da177e4 LT |
423 | struct tasklet_head |
424 | { | |
48f20a9a OJ |
425 | struct tasklet_struct *head; |
426 | struct tasklet_struct **tail; | |
1da177e4 LT |
427 | }; |
428 | ||
4620b49f VN |
429 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
430 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); | |
1da177e4 | 431 | |
7ad5b3a5 | 432 | void __tasklet_schedule(struct tasklet_struct *t) |
1da177e4 LT |
433 | { |
434 | unsigned long flags; | |
435 | ||
436 | local_irq_save(flags); | |
48f20a9a | 437 | t->next = NULL; |
909ea964 CL |
438 | *__this_cpu_read(tasklet_vec.tail) = t; |
439 | __this_cpu_write(tasklet_vec.tail, &(t->next)); | |
1da177e4 LT |
440 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
441 | local_irq_restore(flags); | |
442 | } | |
443 | ||
444 | EXPORT_SYMBOL(__tasklet_schedule); | |
445 | ||
7ad5b3a5 | 446 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
1da177e4 LT |
447 | { |
448 | unsigned long flags; | |
449 | ||
450 | local_irq_save(flags); | |
48f20a9a | 451 | t->next = NULL; |
909ea964 CL |
452 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
453 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); | |
1da177e4 LT |
454 | raise_softirq_irqoff(HI_SOFTIRQ); |
455 | local_irq_restore(flags); | |
456 | } | |
457 | ||
458 | EXPORT_SYMBOL(__tasklet_hi_schedule); | |
459 | ||
7c692cba VN |
460 | void __tasklet_hi_schedule_first(struct tasklet_struct *t) |
461 | { | |
462 | BUG_ON(!irqs_disabled()); | |
463 | ||
909ea964 CL |
464 | t->next = __this_cpu_read(tasklet_hi_vec.head); |
465 | __this_cpu_write(tasklet_hi_vec.head, t); | |
7c692cba VN |
466 | __raise_softirq_irqoff(HI_SOFTIRQ); |
467 | } | |
468 | ||
469 | EXPORT_SYMBOL(__tasklet_hi_schedule_first); | |
470 | ||
1da177e4 LT |
471 | static void tasklet_action(struct softirq_action *a) |
472 | { | |
473 | struct tasklet_struct *list; | |
474 | ||
475 | local_irq_disable(); | |
909ea964 CL |
476 | list = __this_cpu_read(tasklet_vec.head); |
477 | __this_cpu_write(tasklet_vec.head, NULL); | |
478 | __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head); | |
1da177e4 LT |
479 | local_irq_enable(); |
480 | ||
481 | while (list) { | |
482 | struct tasklet_struct *t = list; | |
483 | ||
484 | list = list->next; | |
485 | ||
486 | if (tasklet_trylock(t)) { | |
487 | if (!atomic_read(&t->count)) { | |
488 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) | |
489 | BUG(); | |
490 | t->func(t->data); | |
491 | tasklet_unlock(t); | |
492 | continue; | |
493 | } | |
494 | tasklet_unlock(t); | |
495 | } | |
496 | ||
497 | local_irq_disable(); | |
48f20a9a | 498 | t->next = NULL; |
909ea964 CL |
499 | *__this_cpu_read(tasklet_vec.tail) = t; |
500 | __this_cpu_write(tasklet_vec.tail, &(t->next)); | |
1da177e4 LT |
501 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
502 | local_irq_enable(); | |
503 | } | |
504 | } | |
505 | ||
506 | static void tasklet_hi_action(struct softirq_action *a) | |
507 | { | |
508 | struct tasklet_struct *list; | |
509 | ||
510 | local_irq_disable(); | |
909ea964 CL |
511 | list = __this_cpu_read(tasklet_hi_vec.head); |
512 | __this_cpu_write(tasklet_hi_vec.head, NULL); | |
513 | __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head); | |
1da177e4 LT |
514 | local_irq_enable(); |
515 | ||
516 | while (list) { | |
517 | struct tasklet_struct *t = list; | |
518 | ||
519 | list = list->next; | |
520 | ||
521 | if (tasklet_trylock(t)) { | |
522 | if (!atomic_read(&t->count)) { | |
523 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) | |
524 | BUG(); | |
525 | t->func(t->data); | |
526 | tasklet_unlock(t); | |
527 | continue; | |
528 | } | |
529 | tasklet_unlock(t); | |
530 | } | |
531 | ||
532 | local_irq_disable(); | |
48f20a9a | 533 | t->next = NULL; |
909ea964 CL |
534 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
535 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); | |
1da177e4 LT |
536 | __raise_softirq_irqoff(HI_SOFTIRQ); |
537 | local_irq_enable(); | |
538 | } | |
539 | } | |
540 | ||
541 | ||
542 | void tasklet_init(struct tasklet_struct *t, | |
543 | void (*func)(unsigned long), unsigned long data) | |
544 | { | |
545 | t->next = NULL; | |
546 | t->state = 0; | |
547 | atomic_set(&t->count, 0); | |
548 | t->func = func; | |
549 | t->data = data; | |
550 | } | |
551 | ||
552 | EXPORT_SYMBOL(tasklet_init); | |
553 | ||
554 | void tasklet_kill(struct tasklet_struct *t) | |
555 | { | |
556 | if (in_interrupt()) | |
557 | printk("Attempt to kill tasklet from interrupt\n"); | |
558 | ||
559 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { | |
79d381c9 | 560 | do { |
1da177e4 | 561 | yield(); |
79d381c9 | 562 | } while (test_bit(TASKLET_STATE_SCHED, &t->state)); |
1da177e4 LT |
563 | } |
564 | tasklet_unlock_wait(t); | |
565 | clear_bit(TASKLET_STATE_SCHED, &t->state); | |
566 | } | |
567 | ||
568 | EXPORT_SYMBOL(tasklet_kill); | |
569 | ||
9ba5f005 PZ |
570 | /* |
571 | * tasklet_hrtimer | |
572 | */ | |
573 | ||
574 | /* | |
b9c30322 PZ |
575 | * The trampoline is called when the hrtimer expires. It schedules a tasklet |
576 | * to run __tasklet_hrtimer_trampoline() which in turn will call the intended | |
577 | * hrtimer callback, but from softirq context. | |
9ba5f005 PZ |
578 | */ |
579 | static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer) | |
580 | { | |
581 | struct tasklet_hrtimer *ttimer = | |
582 | container_of(timer, struct tasklet_hrtimer, timer); | |
583 | ||
b9c30322 PZ |
584 | tasklet_hi_schedule(&ttimer->tasklet); |
585 | return HRTIMER_NORESTART; | |
9ba5f005 PZ |
586 | } |
587 | ||
588 | /* | |
589 | * Helper function which calls the hrtimer callback from | |
590 | * tasklet/softirq context | |
591 | */ | |
592 | static void __tasklet_hrtimer_trampoline(unsigned long data) | |
593 | { | |
594 | struct tasklet_hrtimer *ttimer = (void *)data; | |
595 | enum hrtimer_restart restart; | |
596 | ||
597 | restart = ttimer->function(&ttimer->timer); | |
598 | if (restart != HRTIMER_NORESTART) | |
599 | hrtimer_restart(&ttimer->timer); | |
600 | } | |
601 | ||
602 | /** | |
603 | * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks | |
604 | * @ttimer: tasklet_hrtimer which is initialized | |
25985edc | 605 | * @function: hrtimer callback function which gets called from softirq context |
9ba5f005 PZ |
606 | * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME) |
607 | * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL) | |
608 | */ | |
609 | void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer, | |
610 | enum hrtimer_restart (*function)(struct hrtimer *), | |
611 | clockid_t which_clock, enum hrtimer_mode mode) | |
612 | { | |
613 | hrtimer_init(&ttimer->timer, which_clock, mode); | |
614 | ttimer->timer.function = __hrtimer_tasklet_trampoline; | |
615 | tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline, | |
616 | (unsigned long)ttimer); | |
617 | ttimer->function = function; | |
618 | } | |
619 | EXPORT_SYMBOL_GPL(tasklet_hrtimer_init); | |
620 | ||
621 | /* | |
622 | * Remote softirq bits | |
623 | */ | |
624 | ||
54514a70 DM |
625 | DEFINE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); |
626 | EXPORT_PER_CPU_SYMBOL(softirq_work_list); | |
627 | ||
628 | static void __local_trigger(struct call_single_data *cp, int softirq) | |
629 | { | |
630 | struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]); | |
631 | ||
632 | list_add_tail(&cp->list, head); | |
633 | ||
634 | /* Trigger the softirq only if the list was previously empty. */ | |
635 | if (head->next == &cp->list) | |
636 | raise_softirq_irqoff(softirq); | |
637 | } | |
638 | ||
639 | #ifdef CONFIG_USE_GENERIC_SMP_HELPERS | |
640 | static void remote_softirq_receive(void *data) | |
641 | { | |
642 | struct call_single_data *cp = data; | |
643 | unsigned long flags; | |
644 | int softirq; | |
645 | ||
3440a1ca | 646 | softirq = *(int *)cp->info; |
54514a70 DM |
647 | local_irq_save(flags); |
648 | __local_trigger(cp, softirq); | |
649 | local_irq_restore(flags); | |
650 | } | |
651 | ||
652 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
653 | { | |
654 | if (cpu_online(cpu)) { | |
655 | cp->func = remote_softirq_receive; | |
3440a1ca | 656 | cp->info = &softirq; |
54514a70 | 657 | cp->flags = 0; |
54514a70 | 658 | |
6e275637 | 659 | __smp_call_function_single(cpu, cp, 0); |
54514a70 DM |
660 | return 0; |
661 | } | |
662 | return 1; | |
663 | } | |
664 | #else /* CONFIG_USE_GENERIC_SMP_HELPERS */ | |
665 | static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
666 | { | |
667 | return 1; | |
668 | } | |
669 | #endif | |
670 | ||
671 | /** | |
672 | * __send_remote_softirq - try to schedule softirq work on a remote cpu | |
673 | * @cp: private SMP call function data area | |
674 | * @cpu: the remote cpu | |
675 | * @this_cpu: the currently executing cpu | |
676 | * @softirq: the softirq for the work | |
677 | * | |
678 | * Attempt to schedule softirq work on a remote cpu. If this cannot be | |
679 | * done, the work is instead queued up on the local cpu. | |
680 | * | |
681 | * Interrupts must be disabled. | |
682 | */ | |
683 | void __send_remote_softirq(struct call_single_data *cp, int cpu, int this_cpu, int softirq) | |
684 | { | |
685 | if (cpu == this_cpu || __try_remote_softirq(cp, cpu, softirq)) | |
686 | __local_trigger(cp, softirq); | |
687 | } | |
688 | EXPORT_SYMBOL(__send_remote_softirq); | |
689 | ||
690 | /** | |
691 | * send_remote_softirq - try to schedule softirq work on a remote cpu | |
692 | * @cp: private SMP call function data area | |
693 | * @cpu: the remote cpu | |
694 | * @softirq: the softirq for the work | |
695 | * | |
696 | * Like __send_remote_softirq except that disabling interrupts and | |
697 | * computing the current cpu is done for the caller. | |
698 | */ | |
699 | void send_remote_softirq(struct call_single_data *cp, int cpu, int softirq) | |
700 | { | |
701 | unsigned long flags; | |
702 | int this_cpu; | |
703 | ||
704 | local_irq_save(flags); | |
705 | this_cpu = smp_processor_id(); | |
706 | __send_remote_softirq(cp, cpu, this_cpu, softirq); | |
707 | local_irq_restore(flags); | |
708 | } | |
709 | EXPORT_SYMBOL(send_remote_softirq); | |
710 | ||
0db0628d | 711 | static int remote_softirq_cpu_notify(struct notifier_block *self, |
54514a70 DM |
712 | unsigned long action, void *hcpu) |
713 | { | |
714 | /* | |
715 | * If a CPU goes away, splice its entries to the current CPU | |
716 | * and trigger a run of the softirq | |
717 | */ | |
718 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { | |
719 | int cpu = (unsigned long) hcpu; | |
720 | int i; | |
721 | ||
722 | local_irq_disable(); | |
723 | for (i = 0; i < NR_SOFTIRQS; i++) { | |
724 | struct list_head *head = &per_cpu(softirq_work_list[i], cpu); | |
725 | struct list_head *local_head; | |
726 | ||
727 | if (list_empty(head)) | |
728 | continue; | |
729 | ||
730 | local_head = &__get_cpu_var(softirq_work_list[i]); | |
731 | list_splice_init(head, local_head); | |
732 | raise_softirq_irqoff(i); | |
733 | } | |
734 | local_irq_enable(); | |
735 | } | |
736 | ||
737 | return NOTIFY_OK; | |
738 | } | |
739 | ||
0db0628d | 740 | static struct notifier_block remote_softirq_cpu_notifier = { |
54514a70 DM |
741 | .notifier_call = remote_softirq_cpu_notify, |
742 | }; | |
743 | ||
1da177e4 LT |
744 | void __init softirq_init(void) |
745 | { | |
48f20a9a OJ |
746 | int cpu; |
747 | ||
748 | for_each_possible_cpu(cpu) { | |
54514a70 DM |
749 | int i; |
750 | ||
48f20a9a OJ |
751 | per_cpu(tasklet_vec, cpu).tail = |
752 | &per_cpu(tasklet_vec, cpu).head; | |
753 | per_cpu(tasklet_hi_vec, cpu).tail = | |
754 | &per_cpu(tasklet_hi_vec, cpu).head; | |
54514a70 DM |
755 | for (i = 0; i < NR_SOFTIRQS; i++) |
756 | INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu)); | |
48f20a9a OJ |
757 | } |
758 | ||
54514a70 DM |
759 | register_hotcpu_notifier(&remote_softirq_cpu_notifier); |
760 | ||
962cf36c CM |
761 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
762 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); | |
1da177e4 LT |
763 | } |
764 | ||
3e339b5d | 765 | static int ksoftirqd_should_run(unsigned int cpu) |
1da177e4 | 766 | { |
3e339b5d TG |
767 | return local_softirq_pending(); |
768 | } | |
1da177e4 | 769 | |
3e339b5d TG |
770 | static void run_ksoftirqd(unsigned int cpu) |
771 | { | |
772 | local_irq_disable(); | |
773 | if (local_softirq_pending()) { | |
774 | __do_softirq(); | |
775 | rcu_note_context_switch(cpu); | |
776 | local_irq_enable(); | |
777 | cond_resched(); | |
778 | return; | |
1da177e4 | 779 | } |
3e339b5d | 780 | local_irq_enable(); |
1da177e4 LT |
781 | } |
782 | ||
783 | #ifdef CONFIG_HOTPLUG_CPU | |
784 | /* | |
785 | * tasklet_kill_immediate is called to remove a tasklet which can already be | |
786 | * scheduled for execution on @cpu. | |
787 | * | |
788 | * Unlike tasklet_kill, this function removes the tasklet | |
789 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. | |
790 | * | |
791 | * When this function is called, @cpu must be in the CPU_DEAD state. | |
792 | */ | |
793 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) | |
794 | { | |
795 | struct tasklet_struct **i; | |
796 | ||
797 | BUG_ON(cpu_online(cpu)); | |
798 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); | |
799 | ||
800 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) | |
801 | return; | |
802 | ||
803 | /* CPU is dead, so no lock needed. */ | |
48f20a9a | 804 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
1da177e4 LT |
805 | if (*i == t) { |
806 | *i = t->next; | |
48f20a9a OJ |
807 | /* If this was the tail element, move the tail ptr */ |
808 | if (*i == NULL) | |
809 | per_cpu(tasklet_vec, cpu).tail = i; | |
1da177e4 LT |
810 | return; |
811 | } | |
812 | } | |
813 | BUG(); | |
814 | } | |
815 | ||
816 | static void takeover_tasklets(unsigned int cpu) | |
817 | { | |
1da177e4 LT |
818 | /* CPU is dead, so no lock needed. */ |
819 | local_irq_disable(); | |
820 | ||
821 | /* Find end, append list for that CPU. */ | |
e5e41723 | 822 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
909ea964 CL |
823 | *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; |
824 | this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); | |
e5e41723 CB |
825 | per_cpu(tasklet_vec, cpu).head = NULL; |
826 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; | |
827 | } | |
1da177e4 LT |
828 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
829 | ||
e5e41723 | 830 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
909ea964 CL |
831 | *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; |
832 | __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); | |
e5e41723 CB |
833 | per_cpu(tasklet_hi_vec, cpu).head = NULL; |
834 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; | |
835 | } | |
1da177e4 LT |
836 | raise_softirq_irqoff(HI_SOFTIRQ); |
837 | ||
838 | local_irq_enable(); | |
839 | } | |
840 | #endif /* CONFIG_HOTPLUG_CPU */ | |
841 | ||
0db0628d | 842 | static int cpu_callback(struct notifier_block *nfb, |
1da177e4 LT |
843 | unsigned long action, |
844 | void *hcpu) | |
845 | { | |
1da177e4 | 846 | switch (action) { |
1da177e4 | 847 | #ifdef CONFIG_HOTPLUG_CPU |
1da177e4 | 848 | case CPU_DEAD: |
3e339b5d TG |
849 | case CPU_DEAD_FROZEN: |
850 | takeover_tasklets((unsigned long)hcpu); | |
1da177e4 LT |
851 | break; |
852 | #endif /* CONFIG_HOTPLUG_CPU */ | |
3e339b5d | 853 | } |
1da177e4 LT |
854 | return NOTIFY_OK; |
855 | } | |
856 | ||
0db0628d | 857 | static struct notifier_block cpu_nfb = { |
1da177e4 LT |
858 | .notifier_call = cpu_callback |
859 | }; | |
860 | ||
3e339b5d TG |
861 | static struct smp_hotplug_thread softirq_threads = { |
862 | .store = &ksoftirqd, | |
863 | .thread_should_run = ksoftirqd_should_run, | |
864 | .thread_fn = run_ksoftirqd, | |
865 | .thread_comm = "ksoftirqd/%u", | |
866 | }; | |
867 | ||
7babe8db | 868 | static __init int spawn_ksoftirqd(void) |
1da177e4 | 869 | { |
1da177e4 | 870 | register_cpu_notifier(&cpu_nfb); |
3e339b5d TG |
871 | |
872 | BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); | |
873 | ||
1da177e4 LT |
874 | return 0; |
875 | } | |
7babe8db | 876 | early_initcall(spawn_ksoftirqd); |
78eef01b | 877 | |
43a25632 YL |
878 | /* |
879 | * [ These __weak aliases are kept in a separate compilation unit, so that | |
880 | * GCC does not inline them incorrectly. ] | |
881 | */ | |
882 | ||
883 | int __init __weak early_irq_init(void) | |
884 | { | |
885 | return 0; | |
886 | } | |
887 | ||
4a046d17 YL |
888 | int __init __weak arch_probe_nr_irqs(void) |
889 | { | |
b683de2b | 890 | return NR_IRQS_LEGACY; |
4a046d17 YL |
891 | } |
892 | ||
43a25632 YL |
893 | int __init __weak arch_early_irq_init(void) |
894 | { | |
895 | return 0; | |
896 | } |