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1 | /* |
2 | * Generic helpers for smp ipi calls |
3 | * |
4 | * (C) Jens Axboe <jens.axboe@oracle.com> 2008 |
5 | */ |
6 | #include <linux/rcupdate.h> |
7 | #include <linux/rculist.h> |
8 | #include <linux/kernel.h> |
9 | #include <linux/module.h> |
10 | #include <linux/percpu.h> |
11 | #include <linux/init.h> |
12 | #include <linux/gfp.h> |
13 | #include <linux/smp.h> |
14 | #include <linux/cpu.h> |
15 | |
16 | #ifdef CONFIG_USE_GENERIC_SMP_HELPERS |
17 | static struct { |
18 | struct list_head queue; |
19 | raw_spinlock_t lock; |
20 | } call_function __cacheline_aligned_in_smp = |
21 | { |
22 | .queue = LIST_HEAD_INIT(call_function.queue), |
23 | .lock = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock), |
24 | }; |
25 | |
26 | enum { |
27 | CSD_FLAG_LOCK = 0x01, |
28 | }; |
29 | |
30 | struct call_function_data { |
31 | struct call_single_data csd; |
32 | atomic_t refs; |
33 | cpumask_var_t cpumask; |
34 | }; |
35 | |
36 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); |
37 | |
38 | struct call_single_queue { |
39 | struct list_head list; |
40 | raw_spinlock_t lock; |
41 | }; |
42 | |
43 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); |
44 | |
45 | static int |
46 | hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) |
47 | { |
48 | long cpu = (long)hcpu; |
49 | struct call_function_data *cfd = &per_cpu(cfd_data, cpu); |
50 | |
51 | switch (action) { |
52 | case CPU_UP_PREPARE: |
53 | case CPU_UP_PREPARE_FROZEN: |
54 | if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, |
55 | cpu_to_node(cpu))) |
56 | return notifier_from_errno(-ENOMEM); |
57 | break; |
58 | |
59 | #ifdef CONFIG_HOTPLUG_CPU |
60 | case CPU_UP_CANCELED: |
61 | case CPU_UP_CANCELED_FROZEN: |
62 | |
63 | case CPU_DEAD: |
64 | case CPU_DEAD_FROZEN: |
65 | free_cpumask_var(cfd->cpumask); |
66 | break; |
67 | #endif |
68 | }; |
69 | |
70 | return NOTIFY_OK; |
71 | } |
72 | |
73 | static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { |
74 | .notifier_call = hotplug_cfd, |
75 | }; |
76 | |
77 | static int __cpuinit init_call_single_data(void) |
78 | { |
79 | void *cpu = (void *)(long)smp_processor_id(); |
80 | int i; |
81 | |
82 | for_each_possible_cpu(i) { |
83 | struct call_single_queue *q = &per_cpu(call_single_queue, i); |
84 | |
85 | raw_spin_lock_init(&q->lock); |
86 | INIT_LIST_HEAD(&q->list); |
87 | } |
88 | |
89 | hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); |
90 | register_cpu_notifier(&hotplug_cfd_notifier); |
91 | |
92 | return 0; |
93 | } |
94 | early_initcall(init_call_single_data); |
95 | |
96 | /* |
97 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources |
98 | * |
99 | * For non-synchronous ipi calls the csd can still be in use by the |
100 | * previous function call. For multi-cpu calls its even more interesting |
101 | * as we'll have to ensure no other cpu is observing our csd. |
102 | */ |
103 | static void csd_lock_wait(struct call_single_data *data) |
104 | { |
105 | while (data->flags & CSD_FLAG_LOCK) |
106 | cpu_relax(); |
107 | } |
108 | |
109 | static void csd_lock(struct call_single_data *data) |
110 | { |
111 | csd_lock_wait(data); |
112 | data->flags = CSD_FLAG_LOCK; |
113 | |
114 | /* |
115 | * prevent CPU from reordering the above assignment |
116 | * to ->flags with any subsequent assignments to other |
117 | * fields of the specified call_single_data structure: |
118 | */ |
119 | smp_mb(); |
120 | } |
121 | |
122 | static void csd_unlock(struct call_single_data *data) |
123 | { |
124 | WARN_ON(!(data->flags & CSD_FLAG_LOCK)); |
125 | |
126 | /* |
127 | * ensure we're all done before releasing data: |
128 | */ |
129 | smp_mb(); |
130 | |
131 | data->flags &= ~CSD_FLAG_LOCK; |
132 | } |
133 | |
134 | /* |
135 | * Insert a previously allocated call_single_data element |
136 | * for execution on the given CPU. data must already have |
137 | * ->func, ->info, and ->flags set. |
138 | */ |
139 | static |
140 | void generic_exec_single(int cpu, struct call_single_data *data, int wait) |
141 | { |
142 | struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); |
143 | unsigned long flags; |
144 | int ipi; |
145 | |
146 | raw_spin_lock_irqsave(&dst->lock, flags); |
147 | ipi = list_empty(&dst->list); |
148 | list_add_tail(&data->list, &dst->list); |
149 | raw_spin_unlock_irqrestore(&dst->lock, flags); |
150 | |
151 | /* |
152 | * The list addition should be visible before sending the IPI |
153 | * handler locks the list to pull the entry off it because of |
154 | * normal cache coherency rules implied by spinlocks. |
155 | * |
156 | * If IPIs can go out of order to the cache coherency protocol |
157 | * in an architecture, sufficient synchronisation should be added |
158 | * to arch code to make it appear to obey cache coherency WRT |
159 | * locking and barrier primitives. Generic code isn't really |
160 | * equipped to do the right thing... |
161 | */ |
162 | if (ipi) |
163 | arch_send_call_function_single_ipi(cpu); |
164 | |
165 | if (wait) |
166 | csd_lock_wait(data); |
167 | } |
168 | |
169 | /* |
170 | * Invoked by arch to handle an IPI for call function. Must be called with |
171 | * interrupts disabled. |
172 | */ |
173 | void generic_smp_call_function_interrupt(void) |
174 | { |
175 | struct call_function_data *data; |
176 | int cpu = smp_processor_id(); |
177 | |
178 | /* |
179 | * Shouldn't receive this interrupt on a cpu that is not yet online. |
180 | */ |
181 | WARN_ON_ONCE(!cpu_online(cpu)); |
182 | |
183 | /* |
184 | * Ensure entry is visible on call_function_queue after we have |
185 | * entered the IPI. See comment in smp_call_function_many. |
186 | * If we don't have this, then we may miss an entry on the list |
187 | * and never get another IPI to process it. |
188 | */ |
189 | smp_mb(); |
190 | |
191 | /* |
192 | * It's ok to use list_for_each_rcu() here even though we may |
193 | * delete 'pos', since list_del_rcu() doesn't clear ->next |
194 | */ |
195 | list_for_each_entry_rcu(data, &call_function.queue, csd.list) { |
196 | int refs; |
197 | void (*func) (void *info); |
198 | |
199 | /* |
200 | * Since we walk the list without any locks, we might |
201 | * see an entry that was completed, removed from the |
202 | * list and is in the process of being reused. |
203 | * |
204 | * We must check that the cpu is in the cpumask before |
205 | * checking the refs, and both must be set before |
206 | * executing the callback on this cpu. |
207 | */ |
208 | |
209 | if (!cpumask_test_cpu(cpu, data->cpumask)) |
210 | continue; |
211 | |
212 | smp_rmb(); |
213 | |
214 | if (atomic_read(&data->refs) == 0) |
215 | continue; |
216 | |
217 | func = data->csd.func; /* for later warn */ |
218 | data->csd.func(data->csd.info); |
219 | |
220 | /* |
221 | * If the cpu mask is not still set then it enabled interrupts, |
222 | * we took another smp interrupt, and executed the function |
223 | * twice on this cpu. In theory that copy decremented refs. |
224 | */ |
225 | if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) { |
226 | WARN(1, "%pS enabled interrupts and double executed\n", |
227 | func); |
228 | continue; |
229 | } |
230 | |
231 | refs = atomic_dec_return(&data->refs); |
232 | WARN_ON(refs < 0); |
233 | |
234 | if (refs) |
235 | continue; |
236 | |
237 | WARN_ON(!cpumask_empty(data->cpumask)); |
238 | |
239 | raw_spin_lock(&call_function.lock); |
240 | list_del_rcu(&data->csd.list); |
241 | raw_spin_unlock(&call_function.lock); |
242 | |
243 | csd_unlock(&data->csd); |
244 | } |
245 | |
246 | } |
247 | |
248 | /* |
249 | * Invoked by arch to handle an IPI for call function single. Must be |
250 | * called from the arch with interrupts disabled. |
251 | */ |
252 | void generic_smp_call_function_single_interrupt(void) |
253 | { |
254 | struct call_single_queue *q = &__get_cpu_var(call_single_queue); |
255 | unsigned int data_flags; |
256 | LIST_HEAD(list); |
257 | |
258 | /* |
259 | * Shouldn't receive this interrupt on a cpu that is not yet online. |
260 | */ |
261 | WARN_ON_ONCE(!cpu_online(smp_processor_id())); |
262 | |
263 | raw_spin_lock(&q->lock); |
264 | list_replace_init(&q->list, &list); |
265 | raw_spin_unlock(&q->lock); |
266 | |
267 | while (!list_empty(&list)) { |
268 | struct call_single_data *data; |
269 | |
270 | data = list_entry(list.next, struct call_single_data, list); |
271 | list_del(&data->list); |
272 | |
273 | /* |
274 | * 'data' can be invalid after this call if flags == 0 |
275 | * (when called through generic_exec_single()), |
276 | * so save them away before making the call: |
277 | */ |
278 | data_flags = data->flags; |
279 | |
280 | data->func(data->info); |
281 | |
282 | /* |
283 | * Unlocked CSDs are valid through generic_exec_single(): |
284 | */ |
285 | if (data_flags & CSD_FLAG_LOCK) |
286 | csd_unlock(data); |
287 | } |
288 | } |
289 | |
290 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); |
291 | |
292 | /* |
293 | * smp_call_function_single - Run a function on a specific CPU |
294 | * @func: The function to run. This must be fast and non-blocking. |
295 | * @info: An arbitrary pointer to pass to the function. |
296 | * @wait: If true, wait until function has completed on other CPUs. |
297 | * |
298 | * Returns 0 on success, else a negative status code. |
299 | */ |
300 | int smp_call_function_single(int cpu, smp_call_func_t func, void *info, |
301 | int wait) |
302 | { |
303 | struct call_single_data d = { |
304 | .flags = 0, |
305 | }; |
306 | unsigned long flags; |
307 | int this_cpu; |
308 | int err = 0; |
309 | |
310 | /* |
311 | * prevent preemption and reschedule on another processor, |
312 | * as well as CPU removal |
313 | */ |
314 | this_cpu = get_cpu(); |
315 | |
316 | /* |
317 | * Can deadlock when called with interrupts disabled. |
318 | * We allow cpu's that are not yet online though, as no one else can |
319 | * send smp call function interrupt to this cpu and as such deadlocks |
320 | * can't happen. |
321 | */ |
322 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
323 | && !oops_in_progress); |
324 | |
325 | if (cpu == this_cpu) { |
326 | local_irq_save(flags); |
327 | func(info); |
328 | local_irq_restore(flags); |
329 | } else { |
330 | if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { |
331 | struct call_single_data *data = &d; |
332 | |
333 | if (!wait) |
334 | data = &__get_cpu_var(csd_data); |
335 | |
336 | csd_lock(data); |
337 | |
338 | data->func = func; |
339 | data->info = info; |
340 | generic_exec_single(cpu, data, wait); |
341 | } else { |
342 | err = -ENXIO; /* CPU not online */ |
343 | } |
344 | } |
345 | |
346 | put_cpu(); |
347 | |
348 | return err; |
349 | } |
350 | EXPORT_SYMBOL(smp_call_function_single); |
351 | |
352 | /* |
353 | * smp_call_function_any - Run a function on any of the given cpus |
354 | * @mask: The mask of cpus it can run on. |
355 | * @func: The function to run. This must be fast and non-blocking. |
356 | * @info: An arbitrary pointer to pass to the function. |
357 | * @wait: If true, wait until function has completed. |
358 | * |
359 | * Returns 0 on success, else a negative status code (if no cpus were online). |
360 | * Note that @wait will be implicitly turned on in case of allocation failures, |
361 | * since we fall back to on-stack allocation. |
362 | * |
363 | * Selection preference: |
364 | * 1) current cpu if in @mask |
365 | * 2) any cpu of current node if in @mask |
366 | * 3) any other online cpu in @mask |
367 | */ |
368 | int smp_call_function_any(const struct cpumask *mask, |
369 | smp_call_func_t func, void *info, int wait) |
370 | { |
371 | unsigned int cpu; |
372 | const struct cpumask *nodemask; |
373 | int ret; |
374 | |
375 | /* Try for same CPU (cheapest) */ |
376 | cpu = get_cpu(); |
377 | if (cpumask_test_cpu(cpu, mask)) |
378 | goto call; |
379 | |
380 | /* Try for same node. */ |
381 | nodemask = cpumask_of_node(cpu_to_node(cpu)); |
382 | for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; |
383 | cpu = cpumask_next_and(cpu, nodemask, mask)) { |
384 | if (cpu_online(cpu)) |
385 | goto call; |
386 | } |
387 | |
388 | /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ |
389 | cpu = cpumask_any_and(mask, cpu_online_mask); |
390 | call: |
391 | ret = smp_call_function_single(cpu, func, info, wait); |
392 | put_cpu(); |
393 | return ret; |
394 | } |
395 | EXPORT_SYMBOL_GPL(smp_call_function_any); |
396 | |
397 | /** |
398 | * __smp_call_function_single(): Run a function on a specific CPU |
399 | * @cpu: The CPU to run on. |
400 | * @data: Pre-allocated and setup data structure |
401 | * @wait: If true, wait until function has completed on specified CPU. |
402 | * |
403 | * Like smp_call_function_single(), but allow caller to pass in a |
404 | * pre-allocated data structure. Useful for embedding @data inside |
405 | * other structures, for instance. |
406 | */ |
407 | void __smp_call_function_single(int cpu, struct call_single_data *data, |
408 | int wait) |
409 | { |
410 | unsigned int this_cpu; |
411 | unsigned long flags; |
412 | |
413 | this_cpu = get_cpu(); |
414 | /* |
415 | * Can deadlock when called with interrupts disabled. |
416 | * We allow cpu's that are not yet online though, as no one else can |
417 | * send smp call function interrupt to this cpu and as such deadlocks |
418 | * can't happen. |
419 | */ |
420 | WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() |
421 | && !oops_in_progress); |
422 | |
423 | if (cpu == this_cpu) { |
424 | local_irq_save(flags); |
425 | data->func(data->info); |
426 | local_irq_restore(flags); |
427 | } else { |
428 | csd_lock(data); |
429 | generic_exec_single(cpu, data, wait); |
430 | } |
431 | put_cpu(); |
432 | } |
433 | |
434 | /** |
435 | * smp_call_function_many(): Run a function on a set of other CPUs. |
436 | * @mask: The set of cpus to run on (only runs on online subset). |
437 | * @func: The function to run. This must be fast and non-blocking. |
438 | * @info: An arbitrary pointer to pass to the function. |
439 | * @wait: If true, wait (atomically) until function has completed |
440 | * on other CPUs. |
441 | * |
442 | * If @wait is true, then returns once @func has returned. |
443 | * |
444 | * You must not call this function with disabled interrupts or from a |
445 | * hardware interrupt handler or from a bottom half handler. Preemption |
446 | * must be disabled when calling this function. |
447 | */ |
448 | void smp_call_function_many(const struct cpumask *mask, |
449 | smp_call_func_t func, void *info, bool wait) |
450 | { |
451 | struct call_function_data *data; |
452 | unsigned long flags; |
453 | int cpu, next_cpu, this_cpu = smp_processor_id(); |
454 | |
455 | /* |
456 | * Can deadlock when called with interrupts disabled. |
457 | * We allow cpu's that are not yet online though, as no one else can |
458 | * send smp call function interrupt to this cpu and as such deadlocks |
459 | * can't happen. |
460 | */ |
461 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
462 | && !oops_in_progress && !early_boot_irqs_disabled); |
463 | |
464 | /* So, what's a CPU they want? Ignoring this one. */ |
465 | cpu = cpumask_first_and(mask, cpu_online_mask); |
466 | if (cpu == this_cpu) |
467 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
468 | |
469 | /* No online cpus? We're done. */ |
470 | if (cpu >= nr_cpu_ids) |
471 | return; |
472 | |
473 | /* Do we have another CPU which isn't us? */ |
474 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
475 | if (next_cpu == this_cpu) |
476 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); |
477 | |
478 | /* Fastpath: do that cpu by itself. */ |
479 | if (next_cpu >= nr_cpu_ids) { |
480 | smp_call_function_single(cpu, func, info, wait); |
481 | return; |
482 | } |
483 | |
484 | data = &__get_cpu_var(cfd_data); |
485 | csd_lock(&data->csd); |
486 | BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask)); |
487 | |
488 | data->csd.func = func; |
489 | data->csd.info = info; |
490 | cpumask_and(data->cpumask, mask, cpu_online_mask); |
491 | cpumask_clear_cpu(this_cpu, data->cpumask); |
492 | |
493 | /* |
494 | * To ensure the interrupt handler gets an complete view |
495 | * we order the cpumask and refs writes and order the read |
496 | * of them in the interrupt handler. In addition we may |
497 | * only clear our own cpu bit from the mask. |
498 | */ |
499 | smp_wmb(); |
500 | |
501 | atomic_set(&data->refs, cpumask_weight(data->cpumask)); |
502 | |
503 | raw_spin_lock_irqsave(&call_function.lock, flags); |
504 | /* |
505 | * Place entry at the _HEAD_ of the list, so that any cpu still |
506 | * observing the entry in generic_smp_call_function_interrupt() |
507 | * will not miss any other list entries: |
508 | */ |
509 | list_add_rcu(&data->csd.list, &call_function.queue); |
510 | raw_spin_unlock_irqrestore(&call_function.lock, flags); |
511 | |
512 | /* |
513 | * Make the list addition visible before sending the ipi. |
514 | * (IPIs must obey or appear to obey normal Linux cache |
515 | * coherency rules -- see comment in generic_exec_single). |
516 | */ |
517 | smp_mb(); |
518 | |
519 | /* Send a message to all CPUs in the map */ |
520 | arch_send_call_function_ipi_mask(data->cpumask); |
521 | |
522 | /* Optionally wait for the CPUs to complete */ |
523 | if (wait) |
524 | csd_lock_wait(&data->csd); |
525 | } |
526 | EXPORT_SYMBOL(smp_call_function_many); |
527 | |
528 | /** |
529 | * smp_call_function(): Run a function on all other CPUs. |
530 | * @func: The function to run. This must be fast and non-blocking. |
531 | * @info: An arbitrary pointer to pass to the function. |
532 | * @wait: If true, wait (atomically) until function has completed |
533 | * on other CPUs. |
534 | * |
535 | * Returns 0. |
536 | * |
537 | * If @wait is true, then returns once @func has returned; otherwise |
538 | * it returns just before the target cpu calls @func. |
539 | * |
540 | * You must not call this function with disabled interrupts or from a |
541 | * hardware interrupt handler or from a bottom half handler. |
542 | */ |
543 | int smp_call_function(smp_call_func_t func, void *info, int wait) |
544 | { |
545 | preempt_disable(); |
546 | smp_call_function_many(cpu_online_mask, func, info, wait); |
547 | preempt_enable(); |
548 | |
549 | return 0; |
550 | } |
551 | EXPORT_SYMBOL(smp_call_function); |
552 | |
553 | void ipi_call_lock(void) |
554 | { |
555 | raw_spin_lock(&call_function.lock); |
556 | } |
557 | |
558 | void ipi_call_unlock(void) |
559 | { |
560 | raw_spin_unlock(&call_function.lock); |
561 | } |
562 | |
563 | void ipi_call_lock_irq(void) |
564 | { |
565 | raw_spin_lock_irq(&call_function.lock); |
566 | } |
567 | |
568 | void ipi_call_unlock_irq(void) |
569 | { |
570 | raw_spin_unlock_irq(&call_function.lock); |
571 | } |
572 | #endif /* USE_GENERIC_SMP_HELPERS */ |
573 | |
574 | /* |
575 | * Call a function on all processors. May be used during early boot while |
576 | * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead |
577 | * of local_irq_disable/enable(). |
578 | */ |
579 | int on_each_cpu(void (*func) (void *info), void *info, int wait) |
580 | { |
581 | unsigned long flags; |
582 | int ret = 0; |
583 | |
584 | preempt_disable(); |
585 | ret = smp_call_function(func, info, wait); |
586 | local_irq_save(flags); |
587 | func(info); |
588 | local_irq_restore(flags); |
589 | preempt_enable(); |
590 | return ret; |
591 | } |
592 | EXPORT_SYMBOL(on_each_cpu); |
593 |
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