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3d442233
JA
1/*
2 * Generic helpers for smp ipi calls
3 *
4 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
3d442233 5 */
3d442233 6#include <linux/rcupdate.h>
59190f42 7#include <linux/rculist.h>
641cd4cf 8#include <linux/kernel.h>
9984de1a 9#include <linux/export.h>
0b13fda1
IM
10#include <linux/percpu.h>
11#include <linux/init.h>
5a0e3ad6 12#include <linux/gfp.h>
3d442233 13#include <linux/smp.h>
8969a5ed 14#include <linux/cpu.h>
3d442233 15
3bb5d2ee
SS
16#include "smpboot.h"
17
3d442233 18enum {
6e275637 19 CSD_FLAG_LOCK = 0x01,
c84a83e2 20 CSD_FLAG_WAIT = 0x02,
3d442233
JA
21};
22
23struct call_function_data {
9a46ad6d 24 struct call_single_data __percpu *csd;
0b13fda1 25 cpumask_var_t cpumask;
3d442233
JA
26};
27
e03bcb68
MM
28static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
29
6897fc22 30static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
8969a5ed 31
8d056c48
SB
32static void flush_smp_call_function_queue(bool warn_cpu_offline);
33
8969a5ed
PZ
34static int
35hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
36{
37 long cpu = (long)hcpu;
38 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
39
40 switch (action) {
41 case CPU_UP_PREPARE:
42 case CPU_UP_PREPARE_FROZEN:
eaa95840 43 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
8969a5ed 44 cpu_to_node(cpu)))
80b5184c 45 return notifier_from_errno(-ENOMEM);
9a46ad6d
SL
46 cfd->csd = alloc_percpu(struct call_single_data);
47 if (!cfd->csd) {
48 free_cpumask_var(cfd->cpumask);
49 return notifier_from_errno(-ENOMEM);
50 }
8969a5ed
PZ
51 break;
52
69dd647f 53#ifdef CONFIG_HOTPLUG_CPU
8969a5ed
PZ
54 case CPU_UP_CANCELED:
55 case CPU_UP_CANCELED_FROZEN:
8d056c48 56 /* Fall-through to the CPU_DEAD[_FROZEN] case. */
8969a5ed
PZ
57
58 case CPU_DEAD:
59 case CPU_DEAD_FROZEN:
60 free_cpumask_var(cfd->cpumask);
9a46ad6d 61 free_percpu(cfd->csd);
8969a5ed 62 break;
8d056c48
SB
63
64 case CPU_DYING:
65 case CPU_DYING_FROZEN:
66 /*
67 * The IPIs for the smp-call-function callbacks queued by other
68 * CPUs might arrive late, either due to hardware latencies or
69 * because this CPU disabled interrupts (inside stop-machine)
70 * before the IPIs were sent. So flush out any pending callbacks
71 * explicitly (without waiting for the IPIs to arrive), to
72 * ensure that the outgoing CPU doesn't go offline with work
73 * still pending.
74 */
75 flush_smp_call_function_queue(false);
76 break;
8969a5ed
PZ
77#endif
78 };
79
80 return NOTIFY_OK;
81}
82
0db0628d 83static struct notifier_block hotplug_cfd_notifier = {
0b13fda1 84 .notifier_call = hotplug_cfd,
8969a5ed
PZ
85};
86
d8ad7d11 87void __init call_function_init(void)
3d442233 88{
8969a5ed 89 void *cpu = (void *)(long)smp_processor_id();
3d442233
JA
90 int i;
91
6897fc22
CH
92 for_each_possible_cpu(i)
93 init_llist_head(&per_cpu(call_single_queue, i));
8969a5ed
PZ
94
95 hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
96 register_cpu_notifier(&hotplug_cfd_notifier);
3d442233
JA
97}
98
8969a5ed
PZ
99/*
100 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
101 *
0b13fda1
IM
102 * For non-synchronous ipi calls the csd can still be in use by the
103 * previous function call. For multi-cpu calls its even more interesting
104 * as we'll have to ensure no other cpu is observing our csd.
8969a5ed 105 */
e1d12f32 106static void csd_lock_wait(struct call_single_data *csd)
8969a5ed 107{
e1d12f32 108 while (csd->flags & CSD_FLAG_LOCK)
8969a5ed 109 cpu_relax();
6e275637
PZ
110}
111
e1d12f32 112static void csd_lock(struct call_single_data *csd)
6e275637 113{
e1d12f32
AM
114 csd_lock_wait(csd);
115 csd->flags |= CSD_FLAG_LOCK;
8969a5ed
PZ
116
117 /*
0b13fda1
IM
118 * prevent CPU from reordering the above assignment
119 * to ->flags with any subsequent assignments to other
120 * fields of the specified call_single_data structure:
8969a5ed 121 */
8969a5ed
PZ
122 smp_mb();
123}
124
e1d12f32 125static void csd_unlock(struct call_single_data *csd)
8969a5ed 126{
c84a83e2 127 WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
0b13fda1 128
8969a5ed 129 /*
0b13fda1 130 * ensure we're all done before releasing data:
8969a5ed
PZ
131 */
132 smp_mb();
0b13fda1 133
e1d12f32 134 csd->flags &= ~CSD_FLAG_LOCK;
3d442233
JA
135}
136
8b28499a
FW
137static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
138
3d442233 139/*
0b13fda1
IM
140 * Insert a previously allocated call_single_data element
141 * for execution on the given CPU. data must already have
142 * ->func, ->info, and ->flags set.
3d442233 143 */
8b28499a
FW
144static int generic_exec_single(int cpu, struct call_single_data *csd,
145 smp_call_func_t func, void *info, int wait)
3d442233 146{
8b28499a
FW
147 struct call_single_data csd_stack = { .flags = 0 };
148 unsigned long flags;
149
150
151 if (cpu == smp_processor_id()) {
152 local_irq_save(flags);
153 func(info);
154 local_irq_restore(flags);
155 return 0;
156 }
157
158
159 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu))
160 return -ENXIO;
161
162
163 if (!csd) {
164 csd = &csd_stack;
165 if (!wait)
166 csd = &__get_cpu_var(csd_data);
167 }
168
169 csd_lock(csd);
170
171 csd->func = func;
172 csd->info = info;
173
c84a83e2
JA
174 if (wait)
175 csd->flags |= CSD_FLAG_WAIT;
176
561920a0 177 /*
15d0d3b3
NP
178 * The list addition should be visible before sending the IPI
179 * handler locks the list to pull the entry off it because of
180 * normal cache coherency rules implied by spinlocks.
181 *
182 * If IPIs can go out of order to the cache coherency protocol
183 * in an architecture, sufficient synchronisation should be added
184 * to arch code to make it appear to obey cache coherency WRT
0b13fda1
IM
185 * locking and barrier primitives. Generic code isn't really
186 * equipped to do the right thing...
561920a0 187 */
6897fc22 188 if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
3d442233
JA
189 arch_send_call_function_single_ipi(cpu);
190
191 if (wait)
e1d12f32 192 csd_lock_wait(csd);
8b28499a
FW
193
194 return 0;
3d442233
JA
195}
196
8d056c48
SB
197/**
198 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
199 *
200 * Invoked by arch to handle an IPI for call function single.
201 * Must be called with interrupts disabled.
3d442233
JA
202 */
203void generic_smp_call_function_single_interrupt(void)
204{
8d056c48
SB
205 flush_smp_call_function_queue(true);
206}
207
208/**
209 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
210 *
211 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
212 * offline CPU. Skip this check if set to 'false'.
213 *
214 * Flush any pending smp-call-function callbacks queued on this CPU. This is
215 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
216 * to ensure that all pending IPI callbacks are run before it goes completely
217 * offline.
218 *
219 * Loop through the call_single_queue and run all the queued callbacks.
220 * Must be called with interrupts disabled.
221 */
222static void flush_smp_call_function_queue(bool warn_cpu_offline)
223{
224 struct llist_head *head;
5fd77595
JK
225 struct llist_node *entry;
226 struct call_single_data *csd, *csd_next;
a219ccf4
SB
227 static bool warned;
228
8d056c48
SB
229 WARN_ON(!irqs_disabled());
230
231 head = &__get_cpu_var(call_single_queue);
232 entry = llist_del_all(head);
a219ccf4 233 entry = llist_reverse_order(entry);
3d442233 234
8d056c48
SB
235 /* There shouldn't be any pending callbacks on an offline CPU. */
236 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
237 !warned && !llist_empty(head))) {
a219ccf4
SB
238 warned = true;
239 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
240
241 /*
242 * We don't have to use the _safe() variant here
243 * because we are not invoking the IPI handlers yet.
244 */
245 llist_for_each_entry(csd, entry, llist)
246 pr_warn("IPI callback %pS sent to offline CPU\n",
247 csd->func);
248 }
3d442233 249
5fd77595 250 llist_for_each_entry_safe(csd, csd_next, entry, llist) {
e1d12f32 251 csd->func(csd->info);
46591962 252 csd_unlock(csd);
3d442233
JA
253 }
254}
255
256/*
257 * smp_call_function_single - Run a function on a specific CPU
258 * @func: The function to run. This must be fast and non-blocking.
259 * @info: An arbitrary pointer to pass to the function.
3d442233
JA
260 * @wait: If true, wait until function has completed on other CPUs.
261 *
72f279b2 262 * Returns 0 on success, else a negative status code.
3d442233 263 */
3a5f65df 264int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
8691e5a8 265 int wait)
3d442233 266{
0b13fda1 267 int this_cpu;
8b28499a 268 int err;
3d442233 269
0b13fda1
IM
270 /*
271 * prevent preemption and reschedule on another processor,
272 * as well as CPU removal
273 */
274 this_cpu = get_cpu();
275
269c861b
SS
276 /*
277 * Can deadlock when called with interrupts disabled.
278 * We allow cpu's that are not yet online though, as no one else can
279 * send smp call function interrupt to this cpu and as such deadlocks
280 * can't happen.
281 */
282 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
283 && !oops_in_progress);
3d442233 284
8b28499a 285 err = generic_exec_single(cpu, NULL, func, info, wait);
3d442233
JA
286
287 put_cpu();
0b13fda1 288
f73be6de 289 return err;
3d442233
JA
290}
291EXPORT_SYMBOL(smp_call_function_single);
292
d7877c03 293/**
c46fff2a
FW
294 * smp_call_function_single_async(): Run an asynchronous function on a
295 * specific CPU.
d7877c03
FW
296 * @cpu: The CPU to run on.
297 * @csd: Pre-allocated and setup data structure
d7877c03 298 *
c46fff2a
FW
299 * Like smp_call_function_single(), but the call is asynchonous and
300 * can thus be done from contexts with disabled interrupts.
301 *
302 * The caller passes his own pre-allocated data structure
303 * (ie: embedded in an object) and is responsible for synchronizing it
304 * such that the IPIs performed on the @csd are strictly serialized.
305 *
306 * NOTE: Be careful, there is unfortunately no current debugging facility to
307 * validate the correctness of this serialization.
d7877c03 308 */
c46fff2a 309int smp_call_function_single_async(int cpu, struct call_single_data *csd)
d7877c03
FW
310{
311 int err = 0;
d7877c03 312
fce8ad15
FW
313 preempt_disable();
314 err = generic_exec_single(cpu, csd, csd->func, csd->info, 0);
315 preempt_enable();
d7877c03
FW
316
317 return err;
318}
c46fff2a 319EXPORT_SYMBOL_GPL(smp_call_function_single_async);
d7877c03 320
2ea6dec4
RR
321/*
322 * smp_call_function_any - Run a function on any of the given cpus
323 * @mask: The mask of cpus it can run on.
324 * @func: The function to run. This must be fast and non-blocking.
325 * @info: An arbitrary pointer to pass to the function.
326 * @wait: If true, wait until function has completed.
327 *
328 * Returns 0 on success, else a negative status code (if no cpus were online).
2ea6dec4
RR
329 *
330 * Selection preference:
331 * 1) current cpu if in @mask
332 * 2) any cpu of current node if in @mask
333 * 3) any other online cpu in @mask
334 */
335int smp_call_function_any(const struct cpumask *mask,
3a5f65df 336 smp_call_func_t func, void *info, int wait)
2ea6dec4
RR
337{
338 unsigned int cpu;
339 const struct cpumask *nodemask;
340 int ret;
341
342 /* Try for same CPU (cheapest) */
343 cpu = get_cpu();
344 if (cpumask_test_cpu(cpu, mask))
345 goto call;
346
347 /* Try for same node. */
af2422c4 348 nodemask = cpumask_of_node(cpu_to_node(cpu));
2ea6dec4
RR
349 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
350 cpu = cpumask_next_and(cpu, nodemask, mask)) {
351 if (cpu_online(cpu))
352 goto call;
353 }
354
355 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
356 cpu = cpumask_any_and(mask, cpu_online_mask);
357call:
358 ret = smp_call_function_single(cpu, func, info, wait);
359 put_cpu();
360 return ret;
361}
362EXPORT_SYMBOL_GPL(smp_call_function_any);
363
3d442233 364/**
54b11e6d
RR
365 * smp_call_function_many(): Run a function on a set of other CPUs.
366 * @mask: The set of cpus to run on (only runs on online subset).
3d442233
JA
367 * @func: The function to run. This must be fast and non-blocking.
368 * @info: An arbitrary pointer to pass to the function.
0b13fda1
IM
369 * @wait: If true, wait (atomically) until function has completed
370 * on other CPUs.
3d442233 371 *
72f279b2 372 * If @wait is true, then returns once @func has returned.
3d442233
JA
373 *
374 * You must not call this function with disabled interrupts or from a
375 * hardware interrupt handler or from a bottom half handler. Preemption
376 * must be disabled when calling this function.
377 */
54b11e6d 378void smp_call_function_many(const struct cpumask *mask,
3a5f65df 379 smp_call_func_t func, void *info, bool wait)
3d442233 380{
e1d12f32 381 struct call_function_data *cfd;
9a46ad6d 382 int cpu, next_cpu, this_cpu = smp_processor_id();
3d442233 383
269c861b
SS
384 /*
385 * Can deadlock when called with interrupts disabled.
386 * We allow cpu's that are not yet online though, as no one else can
387 * send smp call function interrupt to this cpu and as such deadlocks
388 * can't happen.
389 */
390 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
bd924e8c 391 && !oops_in_progress && !early_boot_irqs_disabled);
3d442233 392
723aae25 393 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
54b11e6d 394 cpu = cpumask_first_and(mask, cpu_online_mask);
0b13fda1 395 if (cpu == this_cpu)
54b11e6d 396 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
0b13fda1 397
54b11e6d
RR
398 /* No online cpus? We're done. */
399 if (cpu >= nr_cpu_ids)
400 return;
401
402 /* Do we have another CPU which isn't us? */
403 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
0b13fda1 404 if (next_cpu == this_cpu)
54b11e6d
RR
405 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
406
407 /* Fastpath: do that cpu by itself. */
408 if (next_cpu >= nr_cpu_ids) {
409 smp_call_function_single(cpu, func, info, wait);
410 return;
3d442233
JA
411 }
412
e1d12f32 413 cfd = &__get_cpu_var(cfd_data);
45a57919 414
e1d12f32
AM
415 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
416 cpumask_clear_cpu(this_cpu, cfd->cpumask);
723aae25
MM
417
418 /* Some callers race with other cpus changing the passed mask */
e1d12f32 419 if (unlikely(!cpumask_weight(cfd->cpumask)))
723aae25 420 return;
3d442233 421
e1d12f32
AM
422 for_each_cpu(cpu, cfd->cpumask) {
423 struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
9a46ad6d
SL
424
425 csd_lock(csd);
426 csd->func = func;
427 csd->info = info;
6897fc22 428 llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
9a46ad6d 429 }
561920a0 430
3d442233 431 /* Send a message to all CPUs in the map */
73f94550 432 arch_send_call_function_ipi_mask(cfd->cpumask);
3d442233 433
9a46ad6d 434 if (wait) {
e1d12f32
AM
435 for_each_cpu(cpu, cfd->cpumask) {
436 struct call_single_data *csd;
437
438 csd = per_cpu_ptr(cfd->csd, cpu);
9a46ad6d
SL
439 csd_lock_wait(csd);
440 }
441 }
3d442233 442}
54b11e6d 443EXPORT_SYMBOL(smp_call_function_many);
3d442233
JA
444
445/**
446 * smp_call_function(): Run a function on all other CPUs.
447 * @func: The function to run. This must be fast and non-blocking.
448 * @info: An arbitrary pointer to pass to the function.
0b13fda1
IM
449 * @wait: If true, wait (atomically) until function has completed
450 * on other CPUs.
3d442233 451 *
54b11e6d 452 * Returns 0.
3d442233
JA
453 *
454 * If @wait is true, then returns once @func has returned; otherwise
72f279b2 455 * it returns just before the target cpu calls @func.
3d442233
JA
456 *
457 * You must not call this function with disabled interrupts or from a
458 * hardware interrupt handler or from a bottom half handler.
459 */
3a5f65df 460int smp_call_function(smp_call_func_t func, void *info, int wait)
3d442233 461{
3d442233 462 preempt_disable();
54b11e6d 463 smp_call_function_many(cpu_online_mask, func, info, wait);
3d442233 464 preempt_enable();
0b13fda1 465
54b11e6d 466 return 0;
3d442233
JA
467}
468EXPORT_SYMBOL(smp_call_function);
351f8f8e 469
34db18a0
AW
470/* Setup configured maximum number of CPUs to activate */
471unsigned int setup_max_cpus = NR_CPUS;
472EXPORT_SYMBOL(setup_max_cpus);
473
474
475/*
476 * Setup routine for controlling SMP activation
477 *
478 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
479 * activation entirely (the MPS table probe still happens, though).
480 *
481 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
482 * greater than 0, limits the maximum number of CPUs activated in
483 * SMP mode to <NUM>.
484 */
485
486void __weak arch_disable_smp_support(void) { }
487
488static int __init nosmp(char *str)
489{
490 setup_max_cpus = 0;
491 arch_disable_smp_support();
492
493 return 0;
494}
495
496early_param("nosmp", nosmp);
497
498/* this is hard limit */
499static int __init nrcpus(char *str)
500{
501 int nr_cpus;
502
503 get_option(&str, &nr_cpus);
504 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
505 nr_cpu_ids = nr_cpus;
506
507 return 0;
508}
509
510early_param("nr_cpus", nrcpus);
511
512static int __init maxcpus(char *str)
513{
514 get_option(&str, &setup_max_cpus);
515 if (setup_max_cpus == 0)
516 arch_disable_smp_support();
517
518 return 0;
519}
520
521early_param("maxcpus", maxcpus);
522
523/* Setup number of possible processor ids */
524int nr_cpu_ids __read_mostly = NR_CPUS;
525EXPORT_SYMBOL(nr_cpu_ids);
526
527/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
528void __init setup_nr_cpu_ids(void)
529{
530 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
531}
532
a17bce4d
BP
533void __weak smp_announce(void)
534{
535 printk(KERN_INFO "Brought up %d CPUs\n", num_online_cpus());
536}
537
34db18a0
AW
538/* Called by boot processor to activate the rest. */
539void __init smp_init(void)
540{
541 unsigned int cpu;
542
3bb5d2ee
SS
543 idle_threads_init();
544
34db18a0
AW
545 /* FIXME: This should be done in userspace --RR */
546 for_each_present_cpu(cpu) {
547 if (num_online_cpus() >= setup_max_cpus)
548 break;
549 if (!cpu_online(cpu))
550 cpu_up(cpu);
551 }
552
553 /* Any cleanup work */
a17bce4d 554 smp_announce();
34db18a0
AW
555 smp_cpus_done(setup_max_cpus);
556}
557
351f8f8e 558/*
bd924e8c
TH
559 * Call a function on all processors. May be used during early boot while
560 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
561 * of local_irq_disable/enable().
351f8f8e
AW
562 */
563int on_each_cpu(void (*func) (void *info), void *info, int wait)
564{
bd924e8c 565 unsigned long flags;
351f8f8e
AW
566 int ret = 0;
567
568 preempt_disable();
569 ret = smp_call_function(func, info, wait);
bd924e8c 570 local_irq_save(flags);
351f8f8e 571 func(info);
bd924e8c 572 local_irq_restore(flags);
351f8f8e
AW
573 preempt_enable();
574 return ret;
575}
576EXPORT_SYMBOL(on_each_cpu);
3fc498f1
GBY
577
578/**
579 * on_each_cpu_mask(): Run a function on processors specified by
580 * cpumask, which may include the local processor.
581 * @mask: The set of cpus to run on (only runs on online subset).
582 * @func: The function to run. This must be fast and non-blocking.
583 * @info: An arbitrary pointer to pass to the function.
584 * @wait: If true, wait (atomically) until function has completed
585 * on other CPUs.
586 *
587 * If @wait is true, then returns once @func has returned.
588 *
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589 * You must not call this function with disabled interrupts or from a
590 * hardware interrupt handler or from a bottom half handler. The
591 * exception is that it may be used during early boot while
592 * early_boot_irqs_disabled is set.
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593 */
594void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
595 void *info, bool wait)
596{
597 int cpu = get_cpu();
598
599 smp_call_function_many(mask, func, info, wait);
600 if (cpumask_test_cpu(cpu, mask)) {
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601 unsigned long flags;
602 local_irq_save(flags);
3fc498f1 603 func(info);
202da400 604 local_irq_restore(flags);
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605 }
606 put_cpu();
607}
608EXPORT_SYMBOL(on_each_cpu_mask);
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609
610/*
611 * on_each_cpu_cond(): Call a function on each processor for which
612 * the supplied function cond_func returns true, optionally waiting
613 * for all the required CPUs to finish. This may include the local
614 * processor.
615 * @cond_func: A callback function that is passed a cpu id and
616 * the the info parameter. The function is called
617 * with preemption disabled. The function should
618 * return a blooean value indicating whether to IPI
619 * the specified CPU.
620 * @func: The function to run on all applicable CPUs.
621 * This must be fast and non-blocking.
622 * @info: An arbitrary pointer to pass to both functions.
623 * @wait: If true, wait (atomically) until function has
624 * completed on other CPUs.
625 * @gfp_flags: GFP flags to use when allocating the cpumask
626 * used internally by the function.
627 *
628 * The function might sleep if the GFP flags indicates a non
629 * atomic allocation is allowed.
630 *
631 * Preemption is disabled to protect against CPUs going offline but not online.
632 * CPUs going online during the call will not be seen or sent an IPI.
633 *
634 * You must not call this function with disabled interrupts or
635 * from a hardware interrupt handler or from a bottom half handler.
636 */
637void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
638 smp_call_func_t func, void *info, bool wait,
639 gfp_t gfp_flags)
640{
641 cpumask_var_t cpus;
642 int cpu, ret;
643
644 might_sleep_if(gfp_flags & __GFP_WAIT);
645
646 if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
647 preempt_disable();
648 for_each_online_cpu(cpu)
649 if (cond_func(cpu, info))
650 cpumask_set_cpu(cpu, cpus);
651 on_each_cpu_mask(cpus, func, info, wait);
652 preempt_enable();
653 free_cpumask_var(cpus);
654 } else {
655 /*
656 * No free cpumask, bother. No matter, we'll
657 * just have to IPI them one by one.
658 */
659 preempt_disable();
660 for_each_online_cpu(cpu)
661 if (cond_func(cpu, info)) {
662 ret = smp_call_function_single(cpu, func,
663 info, wait);
664 WARN_ON_ONCE(!ret);
665 }
666 preempt_enable();
667 }
668}
669EXPORT_SYMBOL(on_each_cpu_cond);
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670
671static void do_nothing(void *unused)
672{
673}
674
675/**
676 * kick_all_cpus_sync - Force all cpus out of idle
677 *
678 * Used to synchronize the update of pm_idle function pointer. It's
679 * called after the pointer is updated and returns after the dummy
680 * callback function has been executed on all cpus. The execution of
681 * the function can only happen on the remote cpus after they have
682 * left the idle function which had been called via pm_idle function
683 * pointer. So it's guaranteed that nothing uses the previous pointer
684 * anymore.
685 */
686void kick_all_cpus_sync(void)
687{
688 /* Make sure the change is visible before we kick the cpus */
689 smp_mb();
690 smp_call_function(do_nothing, NULL, 1);
691}
692EXPORT_SYMBOL_GPL(kick_all_cpus_sync);