Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Generic helpers for smp ipi calls
4 *
5 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
6 */
7
8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10#include <linux/irq_work.h>
11#include <linux/rcupdate.h>
12#include <linux/rculist.h>
13#include <linux/kernel.h>
14#include <linux/export.h>
15#include <linux/percpu.h>
16#include <linux/init.h>
17#include <linux/gfp.h>
18#include <linux/smp.h>
19#include <linux/cpu.h>
20#include <linux/sched.h>
21#include <linux/sched/idle.h>
22#include <linux/hypervisor.h>
23
24#include "smpboot.h"
25
26enum {
27 CSD_FLAG_LOCK = 0x01,
28 CSD_FLAG_SYNCHRONOUS = 0x02,
29};
30
31struct call_function_data {
32 call_single_data_t __percpu *csd;
33 cpumask_var_t cpumask;
34 cpumask_var_t cpumask_ipi;
35};
36
37static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
38
39static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
40
41static void flush_smp_call_function_queue(bool warn_cpu_offline);
42
43int smpcfd_prepare_cpu(unsigned int cpu)
44{
45 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
46
47 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
48 cpu_to_node(cpu)))
49 return -ENOMEM;
50 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
51 cpu_to_node(cpu))) {
52 free_cpumask_var(cfd->cpumask);
53 return -ENOMEM;
54 }
55 cfd->csd = alloc_percpu(call_single_data_t);
56 if (!cfd->csd) {
57 free_cpumask_var(cfd->cpumask);
58 free_cpumask_var(cfd->cpumask_ipi);
59 return -ENOMEM;
60 }
61
62 return 0;
63}
64
65int smpcfd_dead_cpu(unsigned int cpu)
66{
67 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
68
69 free_cpumask_var(cfd->cpumask);
70 free_cpumask_var(cfd->cpumask_ipi);
71 free_percpu(cfd->csd);
72 return 0;
73}
74
75int smpcfd_dying_cpu(unsigned int cpu)
76{
77 /*
78 * The IPIs for the smp-call-function callbacks queued by other
79 * CPUs might arrive late, either due to hardware latencies or
80 * because this CPU disabled interrupts (inside stop-machine)
81 * before the IPIs were sent. So flush out any pending callbacks
82 * explicitly (without waiting for the IPIs to arrive), to
83 * ensure that the outgoing CPU doesn't go offline with work
84 * still pending.
85 */
86 flush_smp_call_function_queue(false);
87 return 0;
88}
89
90void __init call_function_init(void)
91{
92 int i;
93
94 for_each_possible_cpu(i)
95 init_llist_head(&per_cpu(call_single_queue, i));
96
97 smpcfd_prepare_cpu(smp_processor_id());
98}
99
100/*
101 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
102 *
103 * For non-synchronous ipi calls the csd can still be in use by the
104 * previous function call. For multi-cpu calls its even more interesting
105 * as we'll have to ensure no other cpu is observing our csd.
106 */
107static __always_inline void csd_lock_wait(call_single_data_t *csd)
108{
109 smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
110}
111
112static __always_inline void csd_lock(call_single_data_t *csd)
113{
114 csd_lock_wait(csd);
115 csd->flags |= CSD_FLAG_LOCK;
116
117 /*
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_t structure:
121 */
122 smp_wmb();
123}
124
125static __always_inline void csd_unlock(call_single_data_t *csd)
126{
127 WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
128
129 /*
130 * ensure we're all done before releasing data:
131 */
132 smp_store_release(&csd->flags, 0);
133}
134
135static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data);
136
137/*
138 * Insert a previously allocated call_single_data_t element
139 * for execution on the given CPU. data must already have
140 * ->func, ->info, and ->flags set.
141 */
142static int generic_exec_single(int cpu, call_single_data_t *csd,
143 smp_call_func_t func, void *info)
144{
145 if (cpu == smp_processor_id()) {
146 unsigned long flags;
147
148 /*
149 * We can unlock early even for the synchronous on-stack case,
150 * since we're doing this from the same CPU..
151 */
152 csd_unlock(csd);
153 local_irq_save(flags);
154 func(info);
155 local_irq_restore(flags);
156 return 0;
157 }
158
159
160 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
161 csd_unlock(csd);
162 return -ENXIO;
163 }
164
165 csd->func = func;
166 csd->info = info;
167
168 /*
169 * The list addition should be visible before sending the IPI
170 * handler locks the list to pull the entry off it because of
171 * normal cache coherency rules implied by spinlocks.
172 *
173 * If IPIs can go out of order to the cache coherency protocol
174 * in an architecture, sufficient synchronisation should be added
175 * to arch code to make it appear to obey cache coherency WRT
176 * locking and barrier primitives. Generic code isn't really
177 * equipped to do the right thing...
178 */
179 if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
180 arch_send_call_function_single_ipi(cpu);
181
182 return 0;
183}
184
185/**
186 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
187 *
188 * Invoked by arch to handle an IPI for call function single.
189 * Must be called with interrupts disabled.
190 */
191void generic_smp_call_function_single_interrupt(void)
192{
193 flush_smp_call_function_queue(true);
194}
195
196/**
197 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
198 *
199 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
200 * offline CPU. Skip this check if set to 'false'.
201 *
202 * Flush any pending smp-call-function callbacks queued on this CPU. This is
203 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
204 * to ensure that all pending IPI callbacks are run before it goes completely
205 * offline.
206 *
207 * Loop through the call_single_queue and run all the queued callbacks.
208 * Must be called with interrupts disabled.
209 */
210static void flush_smp_call_function_queue(bool warn_cpu_offline)
211{
212 struct llist_head *head;
213 struct llist_node *entry;
214 call_single_data_t *csd, *csd_next;
215 static bool warned;
216
217 lockdep_assert_irqs_disabled();
218
219 head = this_cpu_ptr(&call_single_queue);
220 entry = llist_del_all(head);
221 entry = llist_reverse_order(entry);
222
223 /* There shouldn't be any pending callbacks on an offline CPU. */
224 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
225 !warned && !llist_empty(head))) {
226 warned = true;
227 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
228
229 /*
230 * We don't have to use the _safe() variant here
231 * because we are not invoking the IPI handlers yet.
232 */
233 llist_for_each_entry(csd, entry, llist)
234 pr_warn("IPI callback %pS sent to offline CPU\n",
235 csd->func);
236 }
237
238 llist_for_each_entry_safe(csd, csd_next, entry, llist) {
239 smp_call_func_t func = csd->func;
240 void *info = csd->info;
241
242 /* Do we wait until *after* callback? */
243 if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
244 func(info);
245 csd_unlock(csd);
246 } else {
247 csd_unlock(csd);
248 func(info);
249 }
250 }
251
252 /*
253 * Handle irq works queued remotely by irq_work_queue_on().
254 * Smp functions above are typically synchronous so they
255 * better run first since some other CPUs may be busy waiting
256 * for them.
257 */
258 irq_work_run();
259}
260
261/*
262 * smp_call_function_single - Run a function on a specific CPU
263 * @func: The function to run. This must be fast and non-blocking.
264 * @info: An arbitrary pointer to pass to the function.
265 * @wait: If true, wait until function has completed on other CPUs.
266 *
267 * Returns 0 on success, else a negative status code.
268 */
269int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
270 int wait)
271{
272 call_single_data_t *csd;
273 call_single_data_t csd_stack = {
274 .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS,
275 };
276 int this_cpu;
277 int err;
278
279 /*
280 * prevent preemption and reschedule on another processor,
281 * as well as CPU removal
282 */
283 this_cpu = get_cpu();
284
285 /*
286 * Can deadlock when called with interrupts disabled.
287 * We allow cpu's that are not yet online though, as no one else can
288 * send smp call function interrupt to this cpu and as such deadlocks
289 * can't happen.
290 */
291 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
292 && !oops_in_progress);
293
294 /*
295 * When @wait we can deadlock when we interrupt between llist_add() and
296 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
297 * csd_lock() on because the interrupt context uses the same csd
298 * storage.
299 */
300 WARN_ON_ONCE(!in_task());
301
302 csd = &csd_stack;
303 if (!wait) {
304 csd = this_cpu_ptr(&csd_data);
305 csd_lock(csd);
306 }
307
308 err = generic_exec_single(cpu, csd, func, info);
309
310 if (wait)
311 csd_lock_wait(csd);
312
313 put_cpu();
314
315 return err;
316}
317EXPORT_SYMBOL(smp_call_function_single);
318
319/**
320 * smp_call_function_single_async(): Run an asynchronous function on a
321 * specific CPU.
322 * @cpu: The CPU to run on.
323 * @csd: Pre-allocated and setup data structure
324 *
325 * Like smp_call_function_single(), but the call is asynchonous and
326 * can thus be done from contexts with disabled interrupts.
327 *
328 * The caller passes his own pre-allocated data structure
329 * (ie: embedded in an object) and is responsible for synchronizing it
330 * such that the IPIs performed on the @csd are strictly serialized.
331 *
332 * NOTE: Be careful, there is unfortunately no current debugging facility to
333 * validate the correctness of this serialization.
334 */
335int smp_call_function_single_async(int cpu, call_single_data_t *csd)
336{
337 int err = 0;
338
339 preempt_disable();
340
341 /* We could deadlock if we have to wait here with interrupts disabled! */
342 if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
343 csd_lock_wait(csd);
344
345 csd->flags = CSD_FLAG_LOCK;
346 smp_wmb();
347
348 err = generic_exec_single(cpu, csd, csd->func, csd->info);
349 preempt_enable();
350
351 return err;
352}
353EXPORT_SYMBOL_GPL(smp_call_function_single_async);
354
355/*
356 * smp_call_function_any - Run a function on any of the given cpus
357 * @mask: The mask of cpus it can run on.
358 * @func: The function to run. This must be fast and non-blocking.
359 * @info: An arbitrary pointer to pass to the function.
360 * @wait: If true, wait until function has completed.
361 *
362 * Returns 0 on success, else a negative status code (if no cpus were online).
363 *
364 * Selection preference:
365 * 1) current cpu if in @mask
366 * 2) any cpu of current node if in @mask
367 * 3) any other online cpu in @mask
368 */
369int smp_call_function_any(const struct cpumask *mask,
370 smp_call_func_t func, void *info, int wait)
371{
372 unsigned int cpu;
373 const struct cpumask *nodemask;
374 int ret;
375
376 /* Try for same CPU (cheapest) */
377 cpu = get_cpu();
378 if (cpumask_test_cpu(cpu, mask))
379 goto call;
380
381 /* Try for same node. */
382 nodemask = cpumask_of_node(cpu_to_node(cpu));
383 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
384 cpu = cpumask_next_and(cpu, nodemask, mask)) {
385 if (cpu_online(cpu))
386 goto call;
387 }
388
389 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
390 cpu = cpumask_any_and(mask, cpu_online_mask);
391call:
392 ret = smp_call_function_single(cpu, func, info, wait);
393 put_cpu();
394 return ret;
395}
396EXPORT_SYMBOL_GPL(smp_call_function_any);
397
398/**
399 * smp_call_function_many(): Run a function on a set of other CPUs.
400 * @mask: The set of cpus to run on (only runs on online subset).
401 * @func: The function to run. This must be fast and non-blocking.
402 * @info: An arbitrary pointer to pass to the function.
403 * @wait: If true, wait (atomically) until function has completed
404 * on other CPUs.
405 *
406 * If @wait is true, then returns once @func has returned.
407 *
408 * You must not call this function with disabled interrupts or from a
409 * hardware interrupt handler or from a bottom half handler. Preemption
410 * must be disabled when calling this function.
411 */
412void smp_call_function_many(const struct cpumask *mask,
413 smp_call_func_t func, void *info, bool wait)
414{
415 struct call_function_data *cfd;
416 int cpu, next_cpu, this_cpu = smp_processor_id();
417
418 /*
419 * Can deadlock when called with interrupts disabled.
420 * We allow cpu's that are not yet online though, as no one else can
421 * send smp call function interrupt to this cpu and as such deadlocks
422 * can't happen.
423 */
424 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
425 && !oops_in_progress && !early_boot_irqs_disabled);
426
427 /*
428 * When @wait we can deadlock when we interrupt between llist_add() and
429 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
430 * csd_lock() on because the interrupt context uses the same csd
431 * storage.
432 */
433 WARN_ON_ONCE(!in_task());
434
435 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
436 cpu = cpumask_first_and(mask, cpu_online_mask);
437 if (cpu == this_cpu)
438 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
439
440 /* No online cpus? We're done. */
441 if (cpu >= nr_cpu_ids)
442 return;
443
444 /* Do we have another CPU which isn't us? */
445 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
446 if (next_cpu == this_cpu)
447 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
448
449 /* Fastpath: do that cpu by itself. */
450 if (next_cpu >= nr_cpu_ids) {
451 smp_call_function_single(cpu, func, info, wait);
452 return;
453 }
454
455 cfd = this_cpu_ptr(&cfd_data);
456
457 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
458 __cpumask_clear_cpu(this_cpu, cfd->cpumask);
459
460 /* Some callers race with other cpus changing the passed mask */
461 if (unlikely(!cpumask_weight(cfd->cpumask)))
462 return;
463
464 cpumask_clear(cfd->cpumask_ipi);
465 for_each_cpu(cpu, cfd->cpumask) {
466 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
467
468 csd_lock(csd);
469 if (wait)
470 csd->flags |= CSD_FLAG_SYNCHRONOUS;
471 csd->func = func;
472 csd->info = info;
473 if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
474 __cpumask_set_cpu(cpu, cfd->cpumask_ipi);
475 }
476
477 /* Send a message to all CPUs in the map */
478 arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
479
480 if (wait) {
481 for_each_cpu(cpu, cfd->cpumask) {
482 call_single_data_t *csd;
483
484 csd = per_cpu_ptr(cfd->csd, cpu);
485 csd_lock_wait(csd);
486 }
487 }
488}
489EXPORT_SYMBOL(smp_call_function_many);
490
491/**
492 * smp_call_function(): Run a function on all other CPUs.
493 * @func: The function to run. This must be fast and non-blocking.
494 * @info: An arbitrary pointer to pass to the function.
495 * @wait: If true, wait (atomically) until function has completed
496 * on other CPUs.
497 *
498 * Returns 0.
499 *
500 * If @wait is true, then returns once @func has returned; otherwise
501 * it returns just before the target cpu calls @func.
502 *
503 * You must not call this function with disabled interrupts or from a
504 * hardware interrupt handler or from a bottom half handler.
505 */
506void smp_call_function(smp_call_func_t func, void *info, int wait)
507{
508 preempt_disable();
509 smp_call_function_many(cpu_online_mask, func, info, wait);
510 preempt_enable();
511}
512EXPORT_SYMBOL(smp_call_function);
513
514/* Setup configured maximum number of CPUs to activate */
515unsigned int setup_max_cpus = NR_CPUS;
516EXPORT_SYMBOL(setup_max_cpus);
517
518
519/*
520 * Setup routine for controlling SMP activation
521 *
522 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
523 * activation entirely (the MPS table probe still happens, though).
524 *
525 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
526 * greater than 0, limits the maximum number of CPUs activated in
527 * SMP mode to <NUM>.
528 */
529
530void __weak arch_disable_smp_support(void) { }
531
532static int __init nosmp(char *str)
533{
534 setup_max_cpus = 0;
535 arch_disable_smp_support();
536
537 return 0;
538}
539
540early_param("nosmp", nosmp);
541
542/* this is hard limit */
543static int __init nrcpus(char *str)
544{
545 int nr_cpus;
546
547 get_option(&str, &nr_cpus);
548 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
549 nr_cpu_ids = nr_cpus;
550
551 return 0;
552}
553
554early_param("nr_cpus", nrcpus);
555
556static int __init maxcpus(char *str)
557{
558 get_option(&str, &setup_max_cpus);
559 if (setup_max_cpus == 0)
560 arch_disable_smp_support();
561
562 return 0;
563}
564
565early_param("maxcpus", maxcpus);
566
567/* Setup number of possible processor ids */
568unsigned int nr_cpu_ids __read_mostly = NR_CPUS;
569EXPORT_SYMBOL(nr_cpu_ids);
570
571/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
572void __init setup_nr_cpu_ids(void)
573{
574 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
575}
576
577/* Called by boot processor to activate the rest. */
578void __init smp_init(void)
579{
580 int num_nodes, num_cpus;
581 unsigned int cpu;
582
583 idle_threads_init();
584 cpuhp_threads_init();
585
586 pr_info("Bringing up secondary CPUs ...\n");
587
588 /* FIXME: This should be done in userspace --RR */
589 for_each_present_cpu(cpu) {
590 if (num_online_cpus() >= setup_max_cpus)
591 break;
592 if (!cpu_online(cpu))
593 cpu_up(cpu);
594 }
595
596 num_nodes = num_online_nodes();
597 num_cpus = num_online_cpus();
598 pr_info("Brought up %d node%s, %d CPU%s\n",
599 num_nodes, (num_nodes > 1 ? "s" : ""),
600 num_cpus, (num_cpus > 1 ? "s" : ""));
601
602 /* Any cleanup work */
603 smp_cpus_done(setup_max_cpus);
604}
605
606/*
607 * Call a function on all processors. May be used during early boot while
608 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
609 * of local_irq_disable/enable().
610 */
611void on_each_cpu(void (*func) (void *info), void *info, int wait)
612{
613 unsigned long flags;
614
615 preempt_disable();
616 smp_call_function(func, info, wait);
617 local_irq_save(flags);
618 func(info);
619 local_irq_restore(flags);
620 preempt_enable();
621}
622EXPORT_SYMBOL(on_each_cpu);
623
624/**
625 * on_each_cpu_mask(): Run a function on processors specified by
626 * cpumask, which may include the local processor.
627 * @mask: The set of cpus to run on (only runs on online subset).
628 * @func: The function to run. This must be fast and non-blocking.
629 * @info: An arbitrary pointer to pass to the function.
630 * @wait: If true, wait (atomically) until function has completed
631 * on other CPUs.
632 *
633 * If @wait is true, then returns once @func has returned.
634 *
635 * You must not call this function with disabled interrupts or from a
636 * hardware interrupt handler or from a bottom half handler. The
637 * exception is that it may be used during early boot while
638 * early_boot_irqs_disabled is set.
639 */
640void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
641 void *info, bool wait)
642{
643 int cpu = get_cpu();
644
645 smp_call_function_many(mask, func, info, wait);
646 if (cpumask_test_cpu(cpu, mask)) {
647 unsigned long flags;
648 local_irq_save(flags);
649 func(info);
650 local_irq_restore(flags);
651 }
652 put_cpu();
653}
654EXPORT_SYMBOL(on_each_cpu_mask);
655
656/*
657 * on_each_cpu_cond(): Call a function on each processor for which
658 * the supplied function cond_func returns true, optionally waiting
659 * for all the required CPUs to finish. This may include the local
660 * processor.
661 * @cond_func: A callback function that is passed a cpu id and
662 * the the info parameter. The function is called
663 * with preemption disabled. The function should
664 * return a blooean value indicating whether to IPI
665 * the specified CPU.
666 * @func: The function to run on all applicable CPUs.
667 * This must be fast and non-blocking.
668 * @info: An arbitrary pointer to pass to both functions.
669 * @wait: If true, wait (atomically) until function has
670 * completed on other CPUs.
671 * @gfp_flags: GFP flags to use when allocating the cpumask
672 * used internally by the function.
673 *
674 * The function might sleep if the GFP flags indicates a non
675 * atomic allocation is allowed.
676 *
677 * Preemption is disabled to protect against CPUs going offline but not online.
678 * CPUs going online during the call will not be seen or sent an IPI.
679 *
680 * You must not call this function with disabled interrupts or
681 * from a hardware interrupt handler or from a bottom half handler.
682 */
683void on_each_cpu_cond_mask(bool (*cond_func)(int cpu, void *info),
684 smp_call_func_t func, void *info, bool wait,
685 gfp_t gfp_flags, const struct cpumask *mask)
686{
687 cpumask_var_t cpus;
688 int cpu, ret;
689
690 might_sleep_if(gfpflags_allow_blocking(gfp_flags));
691
692 if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
693 preempt_disable();
694 for_each_cpu(cpu, mask)
695 if (cond_func(cpu, info))
696 __cpumask_set_cpu(cpu, cpus);
697 on_each_cpu_mask(cpus, func, info, wait);
698 preempt_enable();
699 free_cpumask_var(cpus);
700 } else {
701 /*
702 * No free cpumask, bother. No matter, we'll
703 * just have to IPI them one by one.
704 */
705 preempt_disable();
706 for_each_cpu(cpu, mask)
707 if (cond_func(cpu, info)) {
708 ret = smp_call_function_single(cpu, func,
709 info, wait);
710 WARN_ON_ONCE(ret);
711 }
712 preempt_enable();
713 }
714}
715EXPORT_SYMBOL(on_each_cpu_cond_mask);
716
717void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
718 smp_call_func_t func, void *info, bool wait,
719 gfp_t gfp_flags)
720{
721 on_each_cpu_cond_mask(cond_func, func, info, wait, gfp_flags,
722 cpu_online_mask);
723}
724EXPORT_SYMBOL(on_each_cpu_cond);
725
726static void do_nothing(void *unused)
727{
728}
729
730/**
731 * kick_all_cpus_sync - Force all cpus out of idle
732 *
733 * Used to synchronize the update of pm_idle function pointer. It's
734 * called after the pointer is updated and returns after the dummy
735 * callback function has been executed on all cpus. The execution of
736 * the function can only happen on the remote cpus after they have
737 * left the idle function which had been called via pm_idle function
738 * pointer. So it's guaranteed that nothing uses the previous pointer
739 * anymore.
740 */
741void kick_all_cpus_sync(void)
742{
743 /* Make sure the change is visible before we kick the cpus */
744 smp_mb();
745 smp_call_function(do_nothing, NULL, 1);
746}
747EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
748
749/**
750 * wake_up_all_idle_cpus - break all cpus out of idle
751 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
752 * including idle polling cpus, for non-idle cpus, we will do nothing
753 * for them.
754 */
755void wake_up_all_idle_cpus(void)
756{
757 int cpu;
758
759 preempt_disable();
760 for_each_online_cpu(cpu) {
761 if (cpu == smp_processor_id())
762 continue;
763
764 wake_up_if_idle(cpu);
765 }
766 preempt_enable();
767}
768EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
769
770/**
771 * smp_call_on_cpu - Call a function on a specific cpu
772 *
773 * Used to call a function on a specific cpu and wait for it to return.
774 * Optionally make sure the call is done on a specified physical cpu via vcpu
775 * pinning in order to support virtualized environments.
776 */
777struct smp_call_on_cpu_struct {
778 struct work_struct work;
779 struct completion done;
780 int (*func)(void *);
781 void *data;
782 int ret;
783 int cpu;
784};
785
786static void smp_call_on_cpu_callback(struct work_struct *work)
787{
788 struct smp_call_on_cpu_struct *sscs;
789
790 sscs = container_of(work, struct smp_call_on_cpu_struct, work);
791 if (sscs->cpu >= 0)
792 hypervisor_pin_vcpu(sscs->cpu);
793 sscs->ret = sscs->func(sscs->data);
794 if (sscs->cpu >= 0)
795 hypervisor_pin_vcpu(-1);
796
797 complete(&sscs->done);
798}
799
800int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
801{
802 struct smp_call_on_cpu_struct sscs = {
803 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
804 .func = func,
805 .data = par,
806 .cpu = phys ? cpu : -1,
807 };
808
809 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
810
811 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
812 return -ENXIO;
813
814 queue_work_on(cpu, system_wq, &sscs.work);
815 wait_for_completion(&sscs.done);
816
817 return sscs.ret;
818}
819EXPORT_SYMBOL_GPL(smp_call_on_cpu);
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
17static 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
26enum {
27 CSD_FLAG_LOCK = 0x01,
28};
29
30struct call_function_data {
31 struct call_single_data csd;
32 atomic_t refs;
33 cpumask_var_t cpumask;
34};
35
36static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
37
38struct call_single_queue {
39 struct list_head list;
40 raw_spinlock_t lock;
41};
42
43static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
44
45static int
46hotplug_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
73static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
74 .notifier_call = hotplug_cfd,
75};
76
77void __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 */
100static void csd_lock_wait(struct call_single_data *data)
101{
102 while (data->flags & CSD_FLAG_LOCK)
103 cpu_relax();
104}
105
106static 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
119static 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 */
136static
137void 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 */
170void 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 */
249void 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
287static 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 */
297int 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}
347EXPORT_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 */
365int 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);
387call:
388 ret = smp_call_function_single(cpu, func, info, wait);
389 put_cpu();
390 return ret;
391}
392EXPORT_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 */
404void __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 */
445void 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}
556EXPORT_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 */
573int 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}
581EXPORT_SYMBOL(smp_call_function);
582
583void ipi_call_lock(void)
584{
585 raw_spin_lock(&call_function.lock);
586}
587
588void ipi_call_unlock(void)
589{
590 raw_spin_unlock(&call_function.lock);
591}
592
593void ipi_call_lock_irq(void)
594{
595 raw_spin_lock_irq(&call_function.lock);
596}
597
598void 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 */
605unsigned int setup_max_cpus = NR_CPUS;
606EXPORT_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
620void __weak arch_disable_smp_support(void) { }
621
622static int __init nosmp(char *str)
623{
624 setup_max_cpus = 0;
625 arch_disable_smp_support();
626
627 return 0;
628}
629
630early_param("nosmp", nosmp);
631
632/* this is hard limit */
633static 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
644early_param("nr_cpus", nrcpus);
645
646static 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
655early_param("maxcpus", maxcpus);
656
657/* Setup number of possible processor ids */
658int nr_cpu_ids __read_mostly = NR_CPUS;
659EXPORT_SYMBOL(nr_cpu_ids);
660
661/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
662void __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. */
668void __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 */
690int 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}
703EXPORT_SYMBOL(on_each_cpu);