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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/export.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 | void __init call_function_init(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 | |
93 | /* |
94 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources |
95 | * |
96 | * For non-synchronous ipi calls the csd can still be in use by the |
97 | * previous function call. For multi-cpu calls its even more interesting |
98 | * as we'll have to ensure no other cpu is observing our csd. |
99 | */ |
100 | static void csd_lock_wait(struct call_single_data *data) |
101 | { |
102 | while (data->flags & CSD_FLAG_LOCK) |
103 | cpu_relax(); |
104 | } |
105 | |
106 | static void csd_lock(struct call_single_data *data) |
107 | { |
108 | csd_lock_wait(data); |
109 | data->flags = CSD_FLAG_LOCK; |
110 | |
111 | /* |
112 | * prevent CPU from reordering the above assignment |
113 | * to ->flags with any subsequent assignments to other |
114 | * fields of the specified call_single_data structure: |
115 | */ |
116 | smp_mb(); |
117 | } |
118 | |
119 | static void csd_unlock(struct call_single_data *data) |
120 | { |
121 | WARN_ON(!(data->flags & CSD_FLAG_LOCK)); |
122 | |
123 | /* |
124 | * ensure we're all done before releasing data: |
125 | */ |
126 | smp_mb(); |
127 | |
128 | data->flags &= ~CSD_FLAG_LOCK; |
129 | } |
130 | |
131 | /* |
132 | * Insert a previously allocated call_single_data element |
133 | * for execution on the given CPU. data must already have |
134 | * ->func, ->info, and ->flags set. |
135 | */ |
136 | static |
137 | void generic_exec_single(int cpu, struct call_single_data *data, int wait) |
138 | { |
139 | struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); |
140 | unsigned long flags; |
141 | int ipi; |
142 | |
143 | raw_spin_lock_irqsave(&dst->lock, flags); |
144 | ipi = list_empty(&dst->list); |
145 | list_add_tail(&data->list, &dst->list); |
146 | raw_spin_unlock_irqrestore(&dst->lock, flags); |
147 | |
148 | /* |
149 | * The list addition should be visible before sending the IPI |
150 | * handler locks the list to pull the entry off it because of |
151 | * normal cache coherency rules implied by spinlocks. |
152 | * |
153 | * If IPIs can go out of order to the cache coherency protocol |
154 | * in an architecture, sufficient synchronisation should be added |
155 | * to arch code to make it appear to obey cache coherency WRT |
156 | * locking and barrier primitives. Generic code isn't really |
157 | * equipped to do the right thing... |
158 | */ |
159 | if (ipi) |
160 | arch_send_call_function_single_ipi(cpu); |
161 | |
162 | if (wait) |
163 | csd_lock_wait(data); |
164 | } |
165 | |
166 | /* |
167 | * Invoked by arch to handle an IPI for call function. Must be called with |
168 | * interrupts disabled. |
169 | */ |
170 | void generic_smp_call_function_interrupt(void) |
171 | { |
172 | struct call_function_data *data; |
173 | int cpu = smp_processor_id(); |
174 | |
175 | /* |
176 | * Shouldn't receive this interrupt on a cpu that is not yet online. |
177 | */ |
178 | WARN_ON_ONCE(!cpu_online(cpu)); |
179 | |
180 | /* |
181 | * Ensure entry is visible on call_function_queue after we have |
182 | * entered the IPI. See comment in smp_call_function_many. |
183 | * If we don't have this, then we may miss an entry on the list |
184 | * and never get another IPI to process it. |
185 | */ |
186 | smp_mb(); |
187 | |
188 | /* |
189 | * It's ok to use list_for_each_rcu() here even though we may |
190 | * delete 'pos', since list_del_rcu() doesn't clear ->next |
191 | */ |
192 | list_for_each_entry_rcu(data, &call_function.queue, csd.list) { |
193 | int refs; |
194 | smp_call_func_t func; |
195 | |
196 | /* |
197 | * Since we walk the list without any locks, we might |
198 | * see an entry that was completed, removed from the |
199 | * list and is in the process of being reused. |
200 | * |
201 | * We must check that the cpu is in the cpumask before |
202 | * checking the refs, and both must be set before |
203 | * executing the callback on this cpu. |
204 | */ |
205 | |
206 | if (!cpumask_test_cpu(cpu, data->cpumask)) |
207 | continue; |
208 | |
209 | smp_rmb(); |
210 | |
211 | if (atomic_read(&data->refs) == 0) |
212 | continue; |
213 | |
214 | func = data->csd.func; /* save for later warn */ |
215 | func(data->csd.info); |
216 | |
217 | /* |
218 | * If the cpu mask is not still set then func enabled |
219 | * interrupts (BUG), and this cpu took another smp call |
220 | * function interrupt and executed func(info) twice |
221 | * on this cpu. That nested execution decremented refs. |
222 | */ |
223 | if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) { |
224 | WARN(1, "%pf enabled interrupts and double executed\n", func); |
225 | continue; |
226 | } |
227 | |
228 | refs = atomic_dec_return(&data->refs); |
229 | WARN_ON(refs < 0); |
230 | |
231 | if (refs) |
232 | continue; |
233 | |
234 | WARN_ON(!cpumask_empty(data->cpumask)); |
235 | |
236 | raw_spin_lock(&call_function.lock); |
237 | list_del_rcu(&data->csd.list); |
238 | raw_spin_unlock(&call_function.lock); |
239 | |
240 | csd_unlock(&data->csd); |
241 | } |
242 | |
243 | } |
244 | |
245 | /* |
246 | * Invoked by arch to handle an IPI for call function single. Must be |
247 | * called from the arch with interrupts disabled. |
248 | */ |
249 | void generic_smp_call_function_single_interrupt(void) |
250 | { |
251 | struct call_single_queue *q = &__get_cpu_var(call_single_queue); |
252 | unsigned int data_flags; |
253 | LIST_HEAD(list); |
254 | |
255 | /* |
256 | * Shouldn't receive this interrupt on a cpu that is not yet online. |
257 | */ |
258 | WARN_ON_ONCE(!cpu_online(smp_processor_id())); |
259 | |
260 | raw_spin_lock(&q->lock); |
261 | list_replace_init(&q->list, &list); |
262 | raw_spin_unlock(&q->lock); |
263 | |
264 | while (!list_empty(&list)) { |
265 | struct call_single_data *data; |
266 | |
267 | data = list_entry(list.next, struct call_single_data, list); |
268 | list_del(&data->list); |
269 | |
270 | /* |
271 | * 'data' can be invalid after this call if flags == 0 |
272 | * (when called through generic_exec_single()), |
273 | * so save them away before making the call: |
274 | */ |
275 | data_flags = data->flags; |
276 | |
277 | data->func(data->info); |
278 | |
279 | /* |
280 | * Unlocked CSDs are valid through generic_exec_single(): |
281 | */ |
282 | if (data_flags & CSD_FLAG_LOCK) |
283 | csd_unlock(data); |
284 | } |
285 | } |
286 | |
287 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); |
288 | |
289 | /* |
290 | * smp_call_function_single - Run a function on a specific CPU |
291 | * @func: The function to run. This must be fast and non-blocking. |
292 | * @info: An arbitrary pointer to pass to the function. |
293 | * @wait: If true, wait until function has completed on other CPUs. |
294 | * |
295 | * Returns 0 on success, else a negative status code. |
296 | */ |
297 | int smp_call_function_single(int cpu, smp_call_func_t func, void *info, |
298 | int wait) |
299 | { |
300 | struct call_single_data d = { |
301 | .flags = 0, |
302 | }; |
303 | unsigned long flags; |
304 | int this_cpu; |
305 | int err = 0; |
306 | |
307 | /* |
308 | * prevent preemption and reschedule on another processor, |
309 | * as well as CPU removal |
310 | */ |
311 | this_cpu = get_cpu(); |
312 | |
313 | /* |
314 | * Can deadlock when called with interrupts disabled. |
315 | * We allow cpu's that are not yet online though, as no one else can |
316 | * send smp call function interrupt to this cpu and as such deadlocks |
317 | * can't happen. |
318 | */ |
319 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
320 | && !oops_in_progress); |
321 | |
322 | if (cpu == this_cpu) { |
323 | local_irq_save(flags); |
324 | func(info); |
325 | local_irq_restore(flags); |
326 | } else { |
327 | if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { |
328 | struct call_single_data *data = &d; |
329 | |
330 | if (!wait) |
331 | data = &__get_cpu_var(csd_data); |
332 | |
333 | csd_lock(data); |
334 | |
335 | data->func = func; |
336 | data->info = info; |
337 | generic_exec_single(cpu, data, wait); |
338 | } else { |
339 | err = -ENXIO; /* CPU not online */ |
340 | } |
341 | } |
342 | |
343 | put_cpu(); |
344 | |
345 | return err; |
346 | } |
347 | EXPORT_SYMBOL(smp_call_function_single); |
348 | |
349 | /* |
350 | * smp_call_function_any - Run a function on any of the given cpus |
351 | * @mask: The mask of cpus it can run on. |
352 | * @func: The function to run. This must be fast and non-blocking. |
353 | * @info: An arbitrary pointer to pass to the function. |
354 | * @wait: If true, wait until function has completed. |
355 | * |
356 | * Returns 0 on success, else a negative status code (if no cpus were online). |
357 | * Note that @wait will be implicitly turned on in case of allocation failures, |
358 | * since we fall back to on-stack allocation. |
359 | * |
360 | * Selection preference: |
361 | * 1) current cpu if in @mask |
362 | * 2) any cpu of current node if in @mask |
363 | * 3) any other online cpu in @mask |
364 | */ |
365 | int smp_call_function_any(const struct cpumask *mask, |
366 | smp_call_func_t func, void *info, int wait) |
367 | { |
368 | unsigned int cpu; |
369 | const struct cpumask *nodemask; |
370 | int ret; |
371 | |
372 | /* Try for same CPU (cheapest) */ |
373 | cpu = get_cpu(); |
374 | if (cpumask_test_cpu(cpu, mask)) |
375 | goto call; |
376 | |
377 | /* Try for same node. */ |
378 | nodemask = cpumask_of_node(cpu_to_node(cpu)); |
379 | for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; |
380 | cpu = cpumask_next_and(cpu, nodemask, mask)) { |
381 | if (cpu_online(cpu)) |
382 | goto call; |
383 | } |
384 | |
385 | /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ |
386 | cpu = cpumask_any_and(mask, cpu_online_mask); |
387 | call: |
388 | ret = smp_call_function_single(cpu, func, info, wait); |
389 | put_cpu(); |
390 | return ret; |
391 | } |
392 | EXPORT_SYMBOL_GPL(smp_call_function_any); |
393 | |
394 | /** |
395 | * __smp_call_function_single(): Run a function on a specific CPU |
396 | * @cpu: The CPU to run on. |
397 | * @data: Pre-allocated and setup data structure |
398 | * @wait: If true, wait until function has completed on specified CPU. |
399 | * |
400 | * Like smp_call_function_single(), but allow caller to pass in a |
401 | * pre-allocated data structure. Useful for embedding @data inside |
402 | * other structures, for instance. |
403 | */ |
404 | void __smp_call_function_single(int cpu, struct call_single_data *data, |
405 | int wait) |
406 | { |
407 | unsigned int this_cpu; |
408 | unsigned long flags; |
409 | |
410 | this_cpu = get_cpu(); |
411 | /* |
412 | * Can deadlock when called with interrupts disabled. |
413 | * We allow cpu's that are not yet online though, as no one else can |
414 | * send smp call function interrupt to this cpu and as such deadlocks |
415 | * can't happen. |
416 | */ |
417 | WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() |
418 | && !oops_in_progress); |
419 | |
420 | if (cpu == this_cpu) { |
421 | local_irq_save(flags); |
422 | data->func(data->info); |
423 | local_irq_restore(flags); |
424 | } else { |
425 | csd_lock(data); |
426 | generic_exec_single(cpu, data, wait); |
427 | } |
428 | put_cpu(); |
429 | } |
430 | |
431 | /** |
432 | * smp_call_function_many(): Run a function on a set of other CPUs. |
433 | * @mask: The set of cpus to run on (only runs on online subset). |
434 | * @func: The function to run. This must be fast and non-blocking. |
435 | * @info: An arbitrary pointer to pass to the function. |
436 | * @wait: If true, wait (atomically) until function has completed |
437 | * on other CPUs. |
438 | * |
439 | * If @wait is true, then returns once @func has returned. |
440 | * |
441 | * You must not call this function with disabled interrupts or from a |
442 | * hardware interrupt handler or from a bottom half handler. Preemption |
443 | * must be disabled when calling this function. |
444 | */ |
445 | void smp_call_function_many(const struct cpumask *mask, |
446 | smp_call_func_t func, void *info, bool wait) |
447 | { |
448 | struct call_function_data *data; |
449 | unsigned long flags; |
450 | int refs, cpu, next_cpu, this_cpu = smp_processor_id(); |
451 | |
452 | /* |
453 | * Can deadlock when called with interrupts disabled. |
454 | * We allow cpu's that are not yet online though, as no one else can |
455 | * send smp call function interrupt to this cpu and as such deadlocks |
456 | * can't happen. |
457 | */ |
458 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
459 | && !oops_in_progress && !early_boot_irqs_disabled); |
460 | |
461 | /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ |
462 | cpu = cpumask_first_and(mask, cpu_online_mask); |
463 | if (cpu == this_cpu) |
464 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
465 | |
466 | /* No online cpus? We're done. */ |
467 | if (cpu >= nr_cpu_ids) |
468 | return; |
469 | |
470 | /* Do we have another CPU which isn't us? */ |
471 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
472 | if (next_cpu == this_cpu) |
473 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); |
474 | |
475 | /* Fastpath: do that cpu by itself. */ |
476 | if (next_cpu >= nr_cpu_ids) { |
477 | smp_call_function_single(cpu, func, info, wait); |
478 | return; |
479 | } |
480 | |
481 | data = &__get_cpu_var(cfd_data); |
482 | csd_lock(&data->csd); |
483 | |
484 | /* This BUG_ON verifies our reuse assertions and can be removed */ |
485 | BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask)); |
486 | |
487 | /* |
488 | * The global call function queue list add and delete are protected |
489 | * by a lock, but the list is traversed without any lock, relying |
490 | * on the rcu list add and delete to allow safe concurrent traversal. |
491 | * We reuse the call function data without waiting for any grace |
492 | * period after some other cpu removes it from the global queue. |
493 | * This means a cpu might find our data block as it is being |
494 | * filled out. |
495 | * |
496 | * We hold off the interrupt handler on the other cpu by |
497 | * ordering our writes to the cpu mask vs our setting of the |
498 | * refs counter. We assert only the cpu owning the data block |
499 | * will set a bit in cpumask, and each bit will only be cleared |
500 | * by the subject cpu. Each cpu must first find its bit is |
501 | * set and then check that refs is set indicating the element is |
502 | * ready to be processed, otherwise it must skip the entry. |
503 | * |
504 | * On the previous iteration refs was set to 0 by another cpu. |
505 | * To avoid the use of transitivity, set the counter to 0 here |
506 | * so the wmb will pair with the rmb in the interrupt handler. |
507 | */ |
508 | atomic_set(&data->refs, 0); /* convert 3rd to 1st party write */ |
509 | |
510 | data->csd.func = func; |
511 | data->csd.info = info; |
512 | |
513 | /* Ensure 0 refs is visible before mask. Also orders func and info */ |
514 | smp_wmb(); |
515 | |
516 | /* We rely on the "and" being processed before the store */ |
517 | cpumask_and(data->cpumask, mask, cpu_online_mask); |
518 | cpumask_clear_cpu(this_cpu, data->cpumask); |
519 | refs = cpumask_weight(data->cpumask); |
520 | |
521 | /* Some callers race with other cpus changing the passed mask */ |
522 | if (unlikely(!refs)) { |
523 | csd_unlock(&data->csd); |
524 | return; |
525 | } |
526 | |
527 | raw_spin_lock_irqsave(&call_function.lock, flags); |
528 | /* |
529 | * Place entry at the _HEAD_ of the list, so that any cpu still |
530 | * observing the entry in generic_smp_call_function_interrupt() |
531 | * will not miss any other list entries: |
532 | */ |
533 | list_add_rcu(&data->csd.list, &call_function.queue); |
534 | /* |
535 | * We rely on the wmb() in list_add_rcu to complete our writes |
536 | * to the cpumask before this write to refs, which indicates |
537 | * data is on the list and is ready to be processed. |
538 | */ |
539 | atomic_set(&data->refs, refs); |
540 | raw_spin_unlock_irqrestore(&call_function.lock, flags); |
541 | |
542 | /* |
543 | * Make the list addition visible before sending the ipi. |
544 | * (IPIs must obey or appear to obey normal Linux cache |
545 | * coherency rules -- see comment in generic_exec_single). |
546 | */ |
547 | smp_mb(); |
548 | |
549 | /* Send a message to all CPUs in the map */ |
550 | arch_send_call_function_ipi_mask(data->cpumask); |
551 | |
552 | /* Optionally wait for the CPUs to complete */ |
553 | if (wait) |
554 | csd_lock_wait(&data->csd); |
555 | } |
556 | EXPORT_SYMBOL(smp_call_function_many); |
557 | |
558 | /** |
559 | * smp_call_function(): Run a function on all other CPUs. |
560 | * @func: The function to run. This must be fast and non-blocking. |
561 | * @info: An arbitrary pointer to pass to the function. |
562 | * @wait: If true, wait (atomically) until function has completed |
563 | * on other CPUs. |
564 | * |
565 | * Returns 0. |
566 | * |
567 | * If @wait is true, then returns once @func has returned; otherwise |
568 | * it returns just before the target cpu calls @func. |
569 | * |
570 | * You must not call this function with disabled interrupts or from a |
571 | * hardware interrupt handler or from a bottom half handler. |
572 | */ |
573 | int smp_call_function(smp_call_func_t func, void *info, int wait) |
574 | { |
575 | preempt_disable(); |
576 | smp_call_function_many(cpu_online_mask, func, info, wait); |
577 | preempt_enable(); |
578 | |
579 | return 0; |
580 | } |
581 | EXPORT_SYMBOL(smp_call_function); |
582 | |
583 | void ipi_call_lock(void) |
584 | { |
585 | raw_spin_lock(&call_function.lock); |
586 | } |
587 | |
588 | void ipi_call_unlock(void) |
589 | { |
590 | raw_spin_unlock(&call_function.lock); |
591 | } |
592 | |
593 | void ipi_call_lock_irq(void) |
594 | { |
595 | raw_spin_lock_irq(&call_function.lock); |
596 | } |
597 | |
598 | void ipi_call_unlock_irq(void) |
599 | { |
600 | raw_spin_unlock_irq(&call_function.lock); |
601 | } |
602 | #endif /* USE_GENERIC_SMP_HELPERS */ |
603 | |
604 | /* Setup configured maximum number of CPUs to activate */ |
605 | unsigned int setup_max_cpus = NR_CPUS; |
606 | EXPORT_SYMBOL(setup_max_cpus); |
607 | |
608 | |
609 | /* |
610 | * Setup routine for controlling SMP activation |
611 | * |
612 | * Command-line option of "nosmp" or "maxcpus=0" will disable SMP |
613 | * activation entirely (the MPS table probe still happens, though). |
614 | * |
615 | * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer |
616 | * greater than 0, limits the maximum number of CPUs activated in |
617 | * SMP mode to <NUM>. |
618 | */ |
619 | |
620 | void __weak arch_disable_smp_support(void) { } |
621 | |
622 | static int __init nosmp(char *str) |
623 | { |
624 | setup_max_cpus = 0; |
625 | arch_disable_smp_support(); |
626 | |
627 | return 0; |
628 | } |
629 | |
630 | early_param("nosmp", nosmp); |
631 | |
632 | /* this is hard limit */ |
633 | static int __init nrcpus(char *str) |
634 | { |
635 | int nr_cpus; |
636 | |
637 | get_option(&str, &nr_cpus); |
638 | if (nr_cpus > 0 && nr_cpus < nr_cpu_ids) |
639 | nr_cpu_ids = nr_cpus; |
640 | |
641 | return 0; |
642 | } |
643 | |
644 | early_param("nr_cpus", nrcpus); |
645 | |
646 | static int __init maxcpus(char *str) |
647 | { |
648 | get_option(&str, &setup_max_cpus); |
649 | if (setup_max_cpus == 0) |
650 | arch_disable_smp_support(); |
651 | |
652 | return 0; |
653 | } |
654 | |
655 | early_param("maxcpus", maxcpus); |
656 | |
657 | /* Setup number of possible processor ids */ |
658 | int nr_cpu_ids __read_mostly = NR_CPUS; |
659 | EXPORT_SYMBOL(nr_cpu_ids); |
660 | |
661 | /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ |
662 | void __init setup_nr_cpu_ids(void) |
663 | { |
664 | nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1; |
665 | } |
666 | |
667 | /* Called by boot processor to activate the rest. */ |
668 | void __init smp_init(void) |
669 | { |
670 | unsigned int cpu; |
671 | |
672 | /* FIXME: This should be done in userspace --RR */ |
673 | for_each_present_cpu(cpu) { |
674 | if (num_online_cpus() >= setup_max_cpus) |
675 | break; |
676 | if (!cpu_online(cpu)) |
677 | cpu_up(cpu); |
678 | } |
679 | |
680 | /* Any cleanup work */ |
681 | printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus()); |
682 | smp_cpus_done(setup_max_cpus); |
683 | } |
684 | |
685 | /* |
686 | * Call a function on all processors. May be used during early boot while |
687 | * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead |
688 | * of local_irq_disable/enable(). |
689 | */ |
690 | int on_each_cpu(void (*func) (void *info), void *info, int wait) |
691 | { |
692 | unsigned long flags; |
693 | int ret = 0; |
694 | |
695 | preempt_disable(); |
696 | ret = smp_call_function(func, info, wait); |
697 | local_irq_save(flags); |
698 | func(info); |
699 | local_irq_restore(flags); |
700 | preempt_enable(); |
701 | return ret; |
702 | } |
703 | EXPORT_SYMBOL(on_each_cpu); |
704 | |
705 | /** |
706 | * on_each_cpu_mask(): Run a function on processors specified by |
707 | * cpumask, which may include the local processor. |
708 | * @mask: The set of cpus to run on (only runs on online subset). |
709 | * @func: The function to run. This must be fast and non-blocking. |
710 | * @info: An arbitrary pointer to pass to the function. |
711 | * @wait: If true, wait (atomically) until function has completed |
712 | * on other CPUs. |
713 | * |
714 | * If @wait is true, then returns once @func has returned. |
715 | * |
716 | * You must not call this function with disabled interrupts or |
717 | * from a hardware interrupt handler or from a bottom half handler. |
718 | */ |
719 | void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, |
720 | void *info, bool wait) |
721 | { |
722 | int cpu = get_cpu(); |
723 | |
724 | smp_call_function_many(mask, func, info, wait); |
725 | if (cpumask_test_cpu(cpu, mask)) { |
726 | local_irq_disable(); |
727 | func(info); |
728 | local_irq_enable(); |
729 | } |
730 | put_cpu(); |
731 | } |
732 | EXPORT_SYMBOL(on_each_cpu_mask); |
733 | |
734 | /* |
735 | * on_each_cpu_cond(): Call a function on each processor for which |
736 | * the supplied function cond_func returns true, optionally waiting |
737 | * for all the required CPUs to finish. This may include the local |
738 | * processor. |
739 | * @cond_func: A callback function that is passed a cpu id and |
740 | * the the info parameter. The function is called |
741 | * with preemption disabled. The function should |
742 | * return a blooean value indicating whether to IPI |
743 | * the specified CPU. |
744 | * @func: The function to run on all applicable CPUs. |
745 | * This must be fast and non-blocking. |
746 | * @info: An arbitrary pointer to pass to both functions. |
747 | * @wait: If true, wait (atomically) until function has |
748 | * completed on other CPUs. |
749 | * @gfp_flags: GFP flags to use when allocating the cpumask |
750 | * used internally by the function. |
751 | * |
752 | * The function might sleep if the GFP flags indicates a non |
753 | * atomic allocation is allowed. |
754 | * |
755 | * Preemption is disabled to protect against CPUs going offline but not online. |
756 | * CPUs going online during the call will not be seen or sent an IPI. |
757 | * |
758 | * You must not call this function with disabled interrupts or |
759 | * from a hardware interrupt handler or from a bottom half handler. |
760 | */ |
761 | void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info), |
762 | smp_call_func_t func, void *info, bool wait, |
763 | gfp_t gfp_flags) |
764 | { |
765 | cpumask_var_t cpus; |
766 | int cpu, ret; |
767 | |
768 | might_sleep_if(gfp_flags & __GFP_WAIT); |
769 | |
770 | if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) { |
771 | preempt_disable(); |
772 | for_each_online_cpu(cpu) |
773 | if (cond_func(cpu, info)) |
774 | cpumask_set_cpu(cpu, cpus); |
775 | on_each_cpu_mask(cpus, func, info, wait); |
776 | preempt_enable(); |
777 | free_cpumask_var(cpus); |
778 | } else { |
779 | /* |
780 | * No free cpumask, bother. No matter, we'll |
781 | * just have to IPI them one by one. |
782 | */ |
783 | preempt_disable(); |
784 | for_each_online_cpu(cpu) |
785 | if (cond_func(cpu, info)) { |
786 | ret = smp_call_function_single(cpu, func, |
787 | info, wait); |
788 | WARN_ON_ONCE(!ret); |
789 | } |
790 | preempt_enable(); |
791 | } |
792 | } |
793 | EXPORT_SYMBOL(on_each_cpu_cond); |
794 |
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