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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#include "smpboot.h"
17
18#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
19static struct {
20 struct list_head queue;
21 raw_spinlock_t lock;
22} call_function __cacheline_aligned_in_smp =
23 {
24 .queue = LIST_HEAD_INIT(call_function.queue),
25 .lock = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock),
26 };
27
28enum {
29 CSD_FLAG_LOCK = 0x01,
30};
31
32struct call_function_data {
33 struct call_single_data csd;
34 atomic_t refs;
35 cpumask_var_t cpumask;
36};
37
38static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
39
40struct call_single_queue {
41 struct list_head list;
42 raw_spinlock_t lock;
43};
44
45static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
46
47static int
48hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
49{
50 long cpu = (long)hcpu;
51 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
52
53 switch (action) {
54 case CPU_UP_PREPARE:
55 case CPU_UP_PREPARE_FROZEN:
56 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
57 cpu_to_node(cpu)))
58 return notifier_from_errno(-ENOMEM);
59 break;
60
61#ifdef CONFIG_HOTPLUG_CPU
62 case CPU_UP_CANCELED:
63 case CPU_UP_CANCELED_FROZEN:
64
65 case CPU_DEAD:
66 case CPU_DEAD_FROZEN:
67 free_cpumask_var(cfd->cpumask);
68 break;
69#endif
70 };
71
72 return NOTIFY_OK;
73}
74
75static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
76 .notifier_call = hotplug_cfd,
77};
78
79void __init call_function_init(void)
80{
81 void *cpu = (void *)(long)smp_processor_id();
82 int i;
83
84 for_each_possible_cpu(i) {
85 struct call_single_queue *q = &per_cpu(call_single_queue, i);
86
87 raw_spin_lock_init(&q->lock);
88 INIT_LIST_HEAD(&q->list);
89 }
90
91 hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
92 register_cpu_notifier(&hotplug_cfd_notifier);
93}
94
95/*
96 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
97 *
98 * For non-synchronous ipi calls the csd can still be in use by the
99 * previous function call. For multi-cpu calls its even more interesting
100 * as we'll have to ensure no other cpu is observing our csd.
101 */
102static void csd_lock_wait(struct call_single_data *data)
103{
104 while (data->flags & CSD_FLAG_LOCK)
105 cpu_relax();
106}
107
108static void csd_lock(struct call_single_data *data)
109{
110 csd_lock_wait(data);
111 data->flags = CSD_FLAG_LOCK;
112
113 /*
114 * prevent CPU from reordering the above assignment
115 * to ->flags with any subsequent assignments to other
116 * fields of the specified call_single_data structure:
117 */
118 smp_mb();
119}
120
121static void csd_unlock(struct call_single_data *data)
122{
123 WARN_ON(!(data->flags & CSD_FLAG_LOCK));
124
125 /*
126 * ensure we're all done before releasing data:
127 */
128 smp_mb();
129
130 data->flags &= ~CSD_FLAG_LOCK;
131}
132
133/*
134 * Insert a previously allocated call_single_data element
135 * for execution on the given CPU. data must already have
136 * ->func, ->info, and ->flags set.
137 */
138static
139void generic_exec_single(int cpu, struct call_single_data *data, int wait)
140{
141 struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
142 unsigned long flags;
143 int ipi;
144
145 raw_spin_lock_irqsave(&dst->lock, flags);
146 ipi = list_empty(&dst->list);
147 list_add_tail(&data->list, &dst->list);
148 raw_spin_unlock_irqrestore(&dst->lock, flags);
149
150 /*
151 * The list addition should be visible before sending the IPI
152 * handler locks the list to pull the entry off it because of
153 * normal cache coherency rules implied by spinlocks.
154 *
155 * If IPIs can go out of order to the cache coherency protocol
156 * in an architecture, sufficient synchronisation should be added
157 * to arch code to make it appear to obey cache coherency WRT
158 * locking and barrier primitives. Generic code isn't really
159 * equipped to do the right thing...
160 */
161 if (ipi)
162 arch_send_call_function_single_ipi(cpu);
163
164 if (wait)
165 csd_lock_wait(data);
166}
167
168/*
169 * Invoked by arch to handle an IPI for call function. Must be called with
170 * interrupts disabled.
171 */
172void generic_smp_call_function_interrupt(void)
173{
174 struct call_function_data *data;
175 int cpu = smp_processor_id();
176
177 /*
178 * Shouldn't receive this interrupt on a cpu that is not yet online.
179 */
180 WARN_ON_ONCE(!cpu_online(cpu));
181
182 /*
183 * Ensure entry is visible on call_function_queue after we have
184 * entered the IPI. See comment in smp_call_function_many.
185 * If we don't have this, then we may miss an entry on the list
186 * and never get another IPI to process it.
187 */
188 smp_mb();
189
190 /*
191 * It's ok to use list_for_each_rcu() here even though we may
192 * delete 'pos', since list_del_rcu() doesn't clear ->next
193 */
194 list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
195 int refs;
196 smp_call_func_t func;
197
198 /*
199 * Since we walk the list without any locks, we might
200 * see an entry that was completed, removed from the
201 * list and is in the process of being reused.
202 *
203 * We must check that the cpu is in the cpumask before
204 * checking the refs, and both must be set before
205 * executing the callback on this cpu.
206 */
207
208 if (!cpumask_test_cpu(cpu, data->cpumask))
209 continue;
210
211 smp_rmb();
212
213 if (atomic_read(&data->refs) == 0)
214 continue;
215
216 func = data->csd.func; /* save for later warn */
217 func(data->csd.info);
218
219 /*
220 * If the cpu mask is not still set then func enabled
221 * interrupts (BUG), and this cpu took another smp call
222 * function interrupt and executed func(info) twice
223 * on this cpu. That nested execution decremented refs.
224 */
225 if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) {
226 WARN(1, "%pf enabled interrupts and double executed\n", func);
227 continue;
228 }
229
230 refs = atomic_dec_return(&data->refs);
231 WARN_ON(refs < 0);
232
233 if (refs)
234 continue;
235
236 WARN_ON(!cpumask_empty(data->cpumask));
237
238 raw_spin_lock(&call_function.lock);
239 list_del_rcu(&data->csd.list);
240 raw_spin_unlock(&call_function.lock);
241
242 csd_unlock(&data->csd);
243 }
244
245}
246
247/*
248 * Invoked by arch to handle an IPI for call function single. Must be
249 * called from the arch with interrupts disabled.
250 */
251void generic_smp_call_function_single_interrupt(void)
252{
253 struct call_single_queue *q = &__get_cpu_var(call_single_queue);
254 unsigned int data_flags;
255 LIST_HEAD(list);
256
257 /*
258 * Shouldn't receive this interrupt on a cpu that is not yet online.
259 */
260 WARN_ON_ONCE(!cpu_online(smp_processor_id()));
261
262 raw_spin_lock(&q->lock);
263 list_replace_init(&q->list, &list);
264 raw_spin_unlock(&q->lock);
265
266 while (!list_empty(&list)) {
267 struct call_single_data *data;
268
269 data = list_entry(list.next, struct call_single_data, list);
270 list_del(&data->list);
271
272 /*
273 * 'data' can be invalid after this call if flags == 0
274 * (when called through generic_exec_single()),
275 * so save them away before making the call:
276 */
277 data_flags = data->flags;
278
279 data->func(data->info);
280
281 /*
282 * Unlocked CSDs are valid through generic_exec_single():
283 */
284 if (data_flags & CSD_FLAG_LOCK)
285 csd_unlock(data);
286 }
287}
288
289static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
290
291/*
292 * smp_call_function_single - Run a function on a specific CPU
293 * @func: The function to run. This must be fast and non-blocking.
294 * @info: An arbitrary pointer to pass to the function.
295 * @wait: If true, wait until function has completed on other CPUs.
296 *
297 * Returns 0 on success, else a negative status code.
298 */
299int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
300 int wait)
301{
302 struct call_single_data d = {
303 .flags = 0,
304 };
305 unsigned long flags;
306 int this_cpu;
307 int err = 0;
308
309 /*
310 * prevent preemption and reschedule on another processor,
311 * as well as CPU removal
312 */
313 this_cpu = get_cpu();
314
315 /*
316 * Can deadlock when called with interrupts disabled.
317 * We allow cpu's that are not yet online though, as no one else can
318 * send smp call function interrupt to this cpu and as such deadlocks
319 * can't happen.
320 */
321 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
322 && !oops_in_progress);
323
324 if (cpu == this_cpu) {
325 local_irq_save(flags);
326 func(info);
327 local_irq_restore(flags);
328 } else {
329 if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
330 struct call_single_data *data = &d;
331
332 if (!wait)
333 data = &__get_cpu_var(csd_data);
334
335 csd_lock(data);
336
337 data->func = func;
338 data->info = info;
339 generic_exec_single(cpu, data, wait);
340 } else {
341 err = -ENXIO; /* CPU not online */
342 }
343 }
344
345 put_cpu();
346
347 return err;
348}
349EXPORT_SYMBOL(smp_call_function_single);
350
351/*
352 * smp_call_function_any - Run a function on any of the given cpus
353 * @mask: The mask of cpus it can run on.
354 * @func: The function to run. This must be fast and non-blocking.
355 * @info: An arbitrary pointer to pass to the function.
356 * @wait: If true, wait until function has completed.
357 *
358 * Returns 0 on success, else a negative status code (if no cpus were online).
359 * Note that @wait will be implicitly turned on in case of allocation failures,
360 * since we fall back to on-stack allocation.
361 *
362 * Selection preference:
363 * 1) current cpu if in @mask
364 * 2) any cpu of current node if in @mask
365 * 3) any other online cpu in @mask
366 */
367int smp_call_function_any(const struct cpumask *mask,
368 smp_call_func_t func, void *info, int wait)
369{
370 unsigned int cpu;
371 const struct cpumask *nodemask;
372 int ret;
373
374 /* Try for same CPU (cheapest) */
375 cpu = get_cpu();
376 if (cpumask_test_cpu(cpu, mask))
377 goto call;
378
379 /* Try for same node. */
380 nodemask = cpumask_of_node(cpu_to_node(cpu));
381 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
382 cpu = cpumask_next_and(cpu, nodemask, mask)) {
383 if (cpu_online(cpu))
384 goto call;
385 }
386
387 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
388 cpu = cpumask_any_and(mask, cpu_online_mask);
389call:
390 ret = smp_call_function_single(cpu, func, info, wait);
391 put_cpu();
392 return ret;
393}
394EXPORT_SYMBOL_GPL(smp_call_function_any);
395
396/**
397 * __smp_call_function_single(): Run a function on a specific CPU
398 * @cpu: The CPU to run on.
399 * @data: Pre-allocated and setup data structure
400 * @wait: If true, wait until function has completed on specified CPU.
401 *
402 * Like smp_call_function_single(), but allow caller to pass in a
403 * pre-allocated data structure. Useful for embedding @data inside
404 * other structures, for instance.
405 */
406void __smp_call_function_single(int cpu, struct call_single_data *data,
407 int wait)
408{
409 unsigned int this_cpu;
410 unsigned long flags;
411
412 this_cpu = get_cpu();
413 /*
414 * Can deadlock when called with interrupts disabled.
415 * We allow cpu's that are not yet online though, as no one else can
416 * send smp call function interrupt to this cpu and as such deadlocks
417 * can't happen.
418 */
419 WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
420 && !oops_in_progress);
421
422 if (cpu == this_cpu) {
423 local_irq_save(flags);
424 data->func(data->info);
425 local_irq_restore(flags);
426 } else {
427 csd_lock(data);
428 generic_exec_single(cpu, data, wait);
429 }
430 put_cpu();
431}
432
433/**
434 * smp_call_function_many(): Run a function on a set of other CPUs.
435 * @mask: The set of cpus to run on (only runs on online subset).
436 * @func: The function to run. This must be fast and non-blocking.
437 * @info: An arbitrary pointer to pass to the function.
438 * @wait: If true, wait (atomically) until function has completed
439 * on other CPUs.
440 *
441 * If @wait is true, then returns once @func has returned.
442 *
443 * You must not call this function with disabled interrupts or from a
444 * hardware interrupt handler or from a bottom half handler. Preemption
445 * must be disabled when calling this function.
446 */
447void smp_call_function_many(const struct cpumask *mask,
448 smp_call_func_t func, void *info, bool wait)
449{
450 struct call_function_data *data;
451 unsigned long flags;
452 int refs, cpu, next_cpu, this_cpu = smp_processor_id();
453
454 /*
455 * Can deadlock when called with interrupts disabled.
456 * We allow cpu's that are not yet online though, as no one else can
457 * send smp call function interrupt to this cpu and as such deadlocks
458 * can't happen.
459 */
460 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
461 && !oops_in_progress && !early_boot_irqs_disabled);
462
463 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
464 cpu = cpumask_first_and(mask, cpu_online_mask);
465 if (cpu == this_cpu)
466 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
467
468 /* No online cpus? We're done. */
469 if (cpu >= nr_cpu_ids)
470 return;
471
472 /* Do we have another CPU which isn't us? */
473 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
474 if (next_cpu == this_cpu)
475 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
476
477 /* Fastpath: do that cpu by itself. */
478 if (next_cpu >= nr_cpu_ids) {
479 smp_call_function_single(cpu, func, info, wait);
480 return;
481 }
482
483 data = &__get_cpu_var(cfd_data);
484 csd_lock(&data->csd);
485
486 /* This BUG_ON verifies our reuse assertions and can be removed */
487 BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask));
488
489 /*
490 * The global call function queue list add and delete are protected
491 * by a lock, but the list is traversed without any lock, relying
492 * on the rcu list add and delete to allow safe concurrent traversal.
493 * We reuse the call function data without waiting for any grace
494 * period after some other cpu removes it from the global queue.
495 * This means a cpu might find our data block as it is being
496 * filled out.
497 *
498 * We hold off the interrupt handler on the other cpu by
499 * ordering our writes to the cpu mask vs our setting of the
500 * refs counter. We assert only the cpu owning the data block
501 * will set a bit in cpumask, and each bit will only be cleared
502 * by the subject cpu. Each cpu must first find its bit is
503 * set and then check that refs is set indicating the element is
504 * ready to be processed, otherwise it must skip the entry.
505 *
506 * On the previous iteration refs was set to 0 by another cpu.
507 * To avoid the use of transitivity, set the counter to 0 here
508 * so the wmb will pair with the rmb in the interrupt handler.
509 */
510 atomic_set(&data->refs, 0); /* convert 3rd to 1st party write */
511
512 data->csd.func = func;
513 data->csd.info = info;
514
515 /* Ensure 0 refs is visible before mask. Also orders func and info */
516 smp_wmb();
517
518 /* We rely on the "and" being processed before the store */
519 cpumask_and(data->cpumask, mask, cpu_online_mask);
520 cpumask_clear_cpu(this_cpu, data->cpumask);
521 refs = cpumask_weight(data->cpumask);
522
523 /* Some callers race with other cpus changing the passed mask */
524 if (unlikely(!refs)) {
525 csd_unlock(&data->csd);
526 return;
527 }
528
529 raw_spin_lock_irqsave(&call_function.lock, flags);
530 /*
531 * Place entry at the _HEAD_ of the list, so that any cpu still
532 * observing the entry in generic_smp_call_function_interrupt()
533 * will not miss any other list entries:
534 */
535 list_add_rcu(&data->csd.list, &call_function.queue);
536 /*
537 * We rely on the wmb() in list_add_rcu to complete our writes
538 * to the cpumask before this write to refs, which indicates
539 * data is on the list and is ready to be processed.
540 */
541 atomic_set(&data->refs, refs);
542 raw_spin_unlock_irqrestore(&call_function.lock, flags);
543
544 /*
545 * Make the list addition visible before sending the ipi.
546 * (IPIs must obey or appear to obey normal Linux cache
547 * coherency rules -- see comment in generic_exec_single).
548 */
549 smp_mb();
550
551 /* Send a message to all CPUs in the map */
552 arch_send_call_function_ipi_mask(data->cpumask);
553
554 /* Optionally wait for the CPUs to complete */
555 if (wait)
556 csd_lock_wait(&data->csd);
557}
558EXPORT_SYMBOL(smp_call_function_many);
559
560/**
561 * smp_call_function(): Run a function on all other CPUs.
562 * @func: The function to run. This must be fast and non-blocking.
563 * @info: An arbitrary pointer to pass to the function.
564 * @wait: If true, wait (atomically) until function has completed
565 * on other CPUs.
566 *
567 * Returns 0.
568 *
569 * If @wait is true, then returns once @func has returned; otherwise
570 * it returns just before the target cpu calls @func.
571 *
572 * You must not call this function with disabled interrupts or from a
573 * hardware interrupt handler or from a bottom half handler.
574 */
575int smp_call_function(smp_call_func_t func, void *info, int wait)
576{
577 preempt_disable();
578 smp_call_function_many(cpu_online_mask, func, info, wait);
579 preempt_enable();
580
581 return 0;
582}
583EXPORT_SYMBOL(smp_call_function);
584
585void ipi_call_lock(void)
586{
587 raw_spin_lock(&call_function.lock);
588}
589
590void ipi_call_unlock(void)
591{
592 raw_spin_unlock(&call_function.lock);
593}
594
595void ipi_call_lock_irq(void)
596{
597 raw_spin_lock_irq(&call_function.lock);
598}
599
600void ipi_call_unlock_irq(void)
601{
602 raw_spin_unlock_irq(&call_function.lock);
603}
604#endif /* USE_GENERIC_SMP_HELPERS */
605
606/* Setup configured maximum number of CPUs to activate */
607unsigned int setup_max_cpus = NR_CPUS;
608EXPORT_SYMBOL(setup_max_cpus);
609
610
611/*
612 * Setup routine for controlling SMP activation
613 *
614 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
615 * activation entirely (the MPS table probe still happens, though).
616 *
617 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
618 * greater than 0, limits the maximum number of CPUs activated in
619 * SMP mode to <NUM>.
620 */
621
622void __weak arch_disable_smp_support(void) { }
623
624static int __init nosmp(char *str)
625{
626 setup_max_cpus = 0;
627 arch_disable_smp_support();
628
629 return 0;
630}
631
632early_param("nosmp", nosmp);
633
634/* this is hard limit */
635static int __init nrcpus(char *str)
636{
637 int nr_cpus;
638
639 get_option(&str, &nr_cpus);
640 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
641 nr_cpu_ids = nr_cpus;
642
643 return 0;
644}
645
646early_param("nr_cpus", nrcpus);
647
648static int __init maxcpus(char *str)
649{
650 get_option(&str, &setup_max_cpus);
651 if (setup_max_cpus == 0)
652 arch_disable_smp_support();
653
654 return 0;
655}
656
657early_param("maxcpus", maxcpus);
658
659/* Setup number of possible processor ids */
660int nr_cpu_ids __read_mostly = NR_CPUS;
661EXPORT_SYMBOL(nr_cpu_ids);
662
663/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
664void __init setup_nr_cpu_ids(void)
665{
666 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
667}
668
669/* Called by boot processor to activate the rest. */
670void __init smp_init(void)
671{
672 unsigned int cpu;
673
674 idle_threads_init();
675
676 /* FIXME: This should be done in userspace --RR */
677 for_each_present_cpu(cpu) {
678 if (num_online_cpus() >= setup_max_cpus)
679 break;
680 if (!cpu_online(cpu))
681 cpu_up(cpu);
682 }
683
684 /* Any cleanup work */
685 printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
686 smp_cpus_done(setup_max_cpus);
687}
688
689/*
690 * Call a function on all processors. May be used during early boot while
691 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
692 * of local_irq_disable/enable().
693 */
694int on_each_cpu(void (*func) (void *info), void *info, int wait)
695{
696 unsigned long flags;
697 int ret = 0;
698
699 preempt_disable();
700 ret = smp_call_function(func, info, wait);
701 local_irq_save(flags);
702 func(info);
703 local_irq_restore(flags);
704 preempt_enable();
705 return ret;
706}
707EXPORT_SYMBOL(on_each_cpu);
708
709/**
710 * on_each_cpu_mask(): Run a function on processors specified by
711 * cpumask, which may include the local processor.
712 * @mask: The set of cpus to run on (only runs on online subset).
713 * @func: The function to run. This must be fast and non-blocking.
714 * @info: An arbitrary pointer to pass to the function.
715 * @wait: If true, wait (atomically) until function has completed
716 * on other CPUs.
717 *
718 * If @wait is true, then returns once @func has returned.
719 *
720 * You must not call this function with disabled interrupts or
721 * from a hardware interrupt handler or from a bottom half handler.
722 */
723void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
724 void *info, bool wait)
725{
726 int cpu = get_cpu();
727
728 smp_call_function_many(mask, func, info, wait);
729 if (cpumask_test_cpu(cpu, mask)) {
730 local_irq_disable();
731 func(info);
732 local_irq_enable();
733 }
734 put_cpu();
735}
736EXPORT_SYMBOL(on_each_cpu_mask);
737
738/*
739 * on_each_cpu_cond(): Call a function on each processor for which
740 * the supplied function cond_func returns true, optionally waiting
741 * for all the required CPUs to finish. This may include the local
742 * processor.
743 * @cond_func: A callback function that is passed a cpu id and
744 * the the info parameter. The function is called
745 * with preemption disabled. The function should
746 * return a blooean value indicating whether to IPI
747 * the specified CPU.
748 * @func: The function to run on all applicable CPUs.
749 * This must be fast and non-blocking.
750 * @info: An arbitrary pointer to pass to both functions.
751 * @wait: If true, wait (atomically) until function has
752 * completed on other CPUs.
753 * @gfp_flags: GFP flags to use when allocating the cpumask
754 * used internally by the function.
755 *
756 * The function might sleep if the GFP flags indicates a non
757 * atomic allocation is allowed.
758 *
759 * Preemption is disabled to protect against CPUs going offline but not online.
760 * CPUs going online during the call will not be seen or sent an IPI.
761 *
762 * You must not call this function with disabled interrupts or
763 * from a hardware interrupt handler or from a bottom half handler.
764 */
765void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
766 smp_call_func_t func, void *info, bool wait,
767 gfp_t gfp_flags)
768{
769 cpumask_var_t cpus;
770 int cpu, ret;
771
772 might_sleep_if(gfp_flags & __GFP_WAIT);
773
774 if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
775 preempt_disable();
776 for_each_online_cpu(cpu)
777 if (cond_func(cpu, info))
778 cpumask_set_cpu(cpu, cpus);
779 on_each_cpu_mask(cpus, func, info, wait);
780 preempt_enable();
781 free_cpumask_var(cpus);
782 } else {
783 /*
784 * No free cpumask, bother. No matter, we'll
785 * just have to IPI them one by one.
786 */
787 preempt_disable();
788 for_each_online_cpu(cpu)
789 if (cond_func(cpu, info)) {
790 ret = smp_call_function_single(cpu, func,
791 info, wait);
792 WARN_ON_ONCE(!ret);
793 }
794 preempt_enable();
795 }
796}
797EXPORT_SYMBOL(on_each_cpu_cond);
798
799static void do_nothing(void *unused)
800{
801}
802
803/**
804 * kick_all_cpus_sync - Force all cpus out of idle
805 *
806 * Used to synchronize the update of pm_idle function pointer. It's
807 * called after the pointer is updated and returns after the dummy
808 * callback function has been executed on all cpus. The execution of
809 * the function can only happen on the remote cpus after they have
810 * left the idle function which had been called via pm_idle function
811 * pointer. So it's guaranteed that nothing uses the previous pointer
812 * anymore.
813 */
814void kick_all_cpus_sync(void)
815{
816 /* Make sure the change is visible before we kick the cpus */
817 smp_mb();
818 smp_call_function(do_nothing, NULL, 1);
819}
820EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
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/interrupt.h>
18#include <linux/gfp.h>
19#include <linux/smp.h>
20#include <linux/cpu.h>
21#include <linux/sched.h>
22#include <linux/sched/idle.h>
23#include <linux/hypervisor.h>
24#include <linux/sched/clock.h>
25#include <linux/nmi.h>
26#include <linux/sched/debug.h>
27#include <linux/jump_label.h>
28#include <linux/string_choices.h>
29
30#include <trace/events/ipi.h>
31#define CREATE_TRACE_POINTS
32#include <trace/events/csd.h>
33#undef CREATE_TRACE_POINTS
34
35#include "smpboot.h"
36#include "sched/smp.h"
37
38#define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK)
39
40struct call_function_data {
41 call_single_data_t __percpu *csd;
42 cpumask_var_t cpumask;
43 cpumask_var_t cpumask_ipi;
44};
45
46static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
47
48static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
49
50static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1);
51
52static void __flush_smp_call_function_queue(bool warn_cpu_offline);
53
54int smpcfd_prepare_cpu(unsigned int cpu)
55{
56 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
57
58 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
59 cpu_to_node(cpu)))
60 return -ENOMEM;
61 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
62 cpu_to_node(cpu))) {
63 free_cpumask_var(cfd->cpumask);
64 return -ENOMEM;
65 }
66 cfd->csd = alloc_percpu(call_single_data_t);
67 if (!cfd->csd) {
68 free_cpumask_var(cfd->cpumask);
69 free_cpumask_var(cfd->cpumask_ipi);
70 return -ENOMEM;
71 }
72
73 return 0;
74}
75
76int smpcfd_dead_cpu(unsigned int cpu)
77{
78 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
79
80 free_cpumask_var(cfd->cpumask);
81 free_cpumask_var(cfd->cpumask_ipi);
82 free_percpu(cfd->csd);
83 return 0;
84}
85
86int smpcfd_dying_cpu(unsigned int cpu)
87{
88 /*
89 * The IPIs for the smp-call-function callbacks queued by other
90 * CPUs might arrive late, either due to hardware latencies or
91 * because this CPU disabled interrupts (inside stop-machine)
92 * before the IPIs were sent. So flush out any pending callbacks
93 * explicitly (without waiting for the IPIs to arrive), to
94 * ensure that the outgoing CPU doesn't go offline with work
95 * still pending.
96 */
97 __flush_smp_call_function_queue(false);
98 irq_work_run();
99 return 0;
100}
101
102void __init call_function_init(void)
103{
104 int i;
105
106 for_each_possible_cpu(i)
107 init_llist_head(&per_cpu(call_single_queue, i));
108
109 smpcfd_prepare_cpu(smp_processor_id());
110}
111
112static __always_inline void
113send_call_function_single_ipi(int cpu)
114{
115 if (call_function_single_prep_ipi(cpu)) {
116 trace_ipi_send_cpu(cpu, _RET_IP_,
117 generic_smp_call_function_single_interrupt);
118 arch_send_call_function_single_ipi(cpu);
119 }
120}
121
122static __always_inline void
123send_call_function_ipi_mask(struct cpumask *mask)
124{
125 trace_ipi_send_cpumask(mask, _RET_IP_,
126 generic_smp_call_function_single_interrupt);
127 arch_send_call_function_ipi_mask(mask);
128}
129
130static __always_inline void
131csd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd)
132{
133 trace_csd_function_entry(func, csd);
134 func(info);
135 trace_csd_function_exit(func, csd);
136}
137
138#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
139
140static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled);
141
142/*
143 * Parse the csdlock_debug= kernel boot parameter.
144 *
145 * If you need to restore the old "ext" value that once provided
146 * additional debugging information, reapply the following commits:
147 *
148 * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging")
149 * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging")
150 */
151static int __init csdlock_debug(char *str)
152{
153 int ret;
154 unsigned int val = 0;
155
156 ret = get_option(&str, &val);
157 if (ret) {
158 if (val)
159 static_branch_enable(&csdlock_debug_enabled);
160 else
161 static_branch_disable(&csdlock_debug_enabled);
162 }
163
164 return 1;
165}
166__setup("csdlock_debug=", csdlock_debug);
167
168static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
169static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
170static DEFINE_PER_CPU(void *, cur_csd_info);
171
172static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */
173module_param(csd_lock_timeout, ulong, 0444);
174static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */
175module_param(panic_on_ipistall, int, 0444);
176
177static atomic_t csd_bug_count = ATOMIC_INIT(0);
178
179/* Record current CSD work for current CPU, NULL to erase. */
180static void __csd_lock_record(call_single_data_t *csd)
181{
182 if (!csd) {
183 smp_mb(); /* NULL cur_csd after unlock. */
184 __this_cpu_write(cur_csd, NULL);
185 return;
186 }
187 __this_cpu_write(cur_csd_func, csd->func);
188 __this_cpu_write(cur_csd_info, csd->info);
189 smp_wmb(); /* func and info before csd. */
190 __this_cpu_write(cur_csd, csd);
191 smp_mb(); /* Update cur_csd before function call. */
192 /* Or before unlock, as the case may be. */
193}
194
195static __always_inline void csd_lock_record(call_single_data_t *csd)
196{
197 if (static_branch_unlikely(&csdlock_debug_enabled))
198 __csd_lock_record(csd);
199}
200
201static int csd_lock_wait_getcpu(call_single_data_t *csd)
202{
203 unsigned int csd_type;
204
205 csd_type = CSD_TYPE(csd);
206 if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC)
207 return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */
208 return -1;
209}
210
211static atomic_t n_csd_lock_stuck;
212
213/**
214 * csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long?
215 *
216 * Returns @true if a CSD-lock acquisition is stuck and has been stuck
217 * long enough for a "non-responsive CSD lock" message to be printed.
218 */
219bool csd_lock_is_stuck(void)
220{
221 return !!atomic_read(&n_csd_lock_stuck);
222}
223
224/*
225 * Complain if too much time spent waiting. Note that only
226 * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU,
227 * so waiting on other types gets much less information.
228 */
229static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages)
230{
231 int cpu = -1;
232 int cpux;
233 bool firsttime;
234 u64 ts2, ts_delta;
235 call_single_data_t *cpu_cur_csd;
236 unsigned int flags = READ_ONCE(csd->node.u_flags);
237 unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC;
238
239 if (!(flags & CSD_FLAG_LOCK)) {
240 if (!unlikely(*bug_id))
241 return true;
242 cpu = csd_lock_wait_getcpu(csd);
243 pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n",
244 *bug_id, raw_smp_processor_id(), cpu);
245 atomic_dec(&n_csd_lock_stuck);
246 return true;
247 }
248
249 ts2 = ktime_get_mono_fast_ns();
250 /* How long since we last checked for a stuck CSD lock.*/
251 ts_delta = ts2 - *ts1;
252 if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) *
253 (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) ||
254 csd_lock_timeout_ns == 0))
255 return false;
256
257 if (ts0 > ts2) {
258 /* Our own sched_clock went backward; don't blame another CPU. */
259 ts_delta = ts0 - ts2;
260 pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta);
261 *ts1 = ts2;
262 return false;
263 }
264
265 firsttime = !*bug_id;
266 if (firsttime)
267 *bug_id = atomic_inc_return(&csd_bug_count);
268 cpu = csd_lock_wait_getcpu(csd);
269 if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
270 cpux = 0;
271 else
272 cpux = cpu;
273 cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */
274 /* How long since this CSD lock was stuck. */
275 ts_delta = ts2 - ts0;
276 pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n",
277 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta,
278 cpu, csd->func, csd->info);
279 (*nmessages)++;
280 if (firsttime)
281 atomic_inc(&n_csd_lock_stuck);
282 /*
283 * If the CSD lock is still stuck after 5 minutes, it is unlikely
284 * to become unstuck. Use a signed comparison to avoid triggering
285 * on underflows when the TSC is out of sync between sockets.
286 */
287 BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC));
288 if (cpu_cur_csd && csd != cpu_cur_csd) {
289 pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",
290 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),
291 READ_ONCE(per_cpu(cur_csd_info, cpux)));
292 } else {
293 pr_alert("\tcsd: CSD lock (#%d) %s.\n",
294 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");
295 }
296 if (cpu >= 0) {
297 if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0))
298 dump_cpu_task(cpu);
299 if (!cpu_cur_csd) {
300 pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
301 arch_send_call_function_single_ipi(cpu);
302 }
303 }
304 if (firsttime)
305 dump_stack();
306 *ts1 = ts2;
307
308 return false;
309}
310
311/*
312 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
313 *
314 * For non-synchronous ipi calls the csd can still be in use by the
315 * previous function call. For multi-cpu calls its even more interesting
316 * as we'll have to ensure no other cpu is observing our csd.
317 */
318static void __csd_lock_wait(call_single_data_t *csd)
319{
320 unsigned long nmessages = 0;
321 int bug_id = 0;
322 u64 ts0, ts1;
323
324 ts1 = ts0 = ktime_get_mono_fast_ns();
325 for (;;) {
326 if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages))
327 break;
328 cpu_relax();
329 }
330 smp_acquire__after_ctrl_dep();
331}
332
333static __always_inline void csd_lock_wait(call_single_data_t *csd)
334{
335 if (static_branch_unlikely(&csdlock_debug_enabled)) {
336 __csd_lock_wait(csd);
337 return;
338 }
339
340 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
341}
342#else
343static void csd_lock_record(call_single_data_t *csd)
344{
345}
346
347static __always_inline void csd_lock_wait(call_single_data_t *csd)
348{
349 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
350}
351#endif
352
353static __always_inline void csd_lock(call_single_data_t *csd)
354{
355 csd_lock_wait(csd);
356 csd->node.u_flags |= CSD_FLAG_LOCK;
357
358 /*
359 * prevent CPU from reordering the above assignment
360 * to ->flags with any subsequent assignments to other
361 * fields of the specified call_single_data_t structure:
362 */
363 smp_wmb();
364}
365
366static __always_inline void csd_unlock(call_single_data_t *csd)
367{
368 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK));
369
370 /*
371 * ensure we're all done before releasing data:
372 */
373 smp_store_release(&csd->node.u_flags, 0);
374}
375
376static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data);
377
378void __smp_call_single_queue(int cpu, struct llist_node *node)
379{
380 /*
381 * We have to check the type of the CSD before queueing it, because
382 * once queued it can have its flags cleared by
383 * flush_smp_call_function_queue()
384 * even if we haven't sent the smp_call IPI yet (e.g. the stopper
385 * executes migration_cpu_stop() on the remote CPU).
386 */
387 if (trace_csd_queue_cpu_enabled()) {
388 call_single_data_t *csd;
389 smp_call_func_t func;
390
391 csd = container_of(node, call_single_data_t, node.llist);
392 func = CSD_TYPE(csd) == CSD_TYPE_TTWU ?
393 sched_ttwu_pending : csd->func;
394
395 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
396 }
397
398 /*
399 * The list addition should be visible to the target CPU when it pops
400 * the head of the list to pull the entry off it in the IPI handler
401 * because of normal cache coherency rules implied by the underlying
402 * llist ops.
403 *
404 * If IPIs can go out of order to the cache coherency protocol
405 * in an architecture, sufficient synchronisation should be added
406 * to arch code to make it appear to obey cache coherency WRT
407 * locking and barrier primitives. Generic code isn't really
408 * equipped to do the right thing...
409 */
410 if (llist_add(node, &per_cpu(call_single_queue, cpu)))
411 send_call_function_single_ipi(cpu);
412}
413
414/*
415 * Insert a previously allocated call_single_data_t element
416 * for execution on the given CPU. data must already have
417 * ->func, ->info, and ->flags set.
418 */
419static int generic_exec_single(int cpu, call_single_data_t *csd)
420{
421 if (cpu == smp_processor_id()) {
422 smp_call_func_t func = csd->func;
423 void *info = csd->info;
424 unsigned long flags;
425
426 /*
427 * We can unlock early even for the synchronous on-stack case,
428 * since we're doing this from the same CPU..
429 */
430 csd_lock_record(csd);
431 csd_unlock(csd);
432 local_irq_save(flags);
433 csd_do_func(func, info, NULL);
434 csd_lock_record(NULL);
435 local_irq_restore(flags);
436 return 0;
437 }
438
439 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
440 csd_unlock(csd);
441 return -ENXIO;
442 }
443
444 __smp_call_single_queue(cpu, &csd->node.llist);
445
446 return 0;
447}
448
449/**
450 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
451 *
452 * Invoked by arch to handle an IPI for call function single.
453 * Must be called with interrupts disabled.
454 */
455void generic_smp_call_function_single_interrupt(void)
456{
457 __flush_smp_call_function_queue(true);
458}
459
460/**
461 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks
462 *
463 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
464 * offline CPU. Skip this check if set to 'false'.
465 *
466 * Flush any pending smp-call-function callbacks queued on this CPU. This is
467 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
468 * to ensure that all pending IPI callbacks are run before it goes completely
469 * offline.
470 *
471 * Loop through the call_single_queue and run all the queued callbacks.
472 * Must be called with interrupts disabled.
473 */
474static void __flush_smp_call_function_queue(bool warn_cpu_offline)
475{
476 call_single_data_t *csd, *csd_next;
477 struct llist_node *entry, *prev;
478 struct llist_head *head;
479 static bool warned;
480 atomic_t *tbt;
481
482 lockdep_assert_irqs_disabled();
483
484 /* Allow waiters to send backtrace NMI from here onwards */
485 tbt = this_cpu_ptr(&trigger_backtrace);
486 atomic_set_release(tbt, 1);
487
488 head = this_cpu_ptr(&call_single_queue);
489 entry = llist_del_all(head);
490 entry = llist_reverse_order(entry);
491
492 /* There shouldn't be any pending callbacks on an offline CPU. */
493 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
494 !warned && entry != NULL)) {
495 warned = true;
496 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
497
498 /*
499 * We don't have to use the _safe() variant here
500 * because we are not invoking the IPI handlers yet.
501 */
502 llist_for_each_entry(csd, entry, node.llist) {
503 switch (CSD_TYPE(csd)) {
504 case CSD_TYPE_ASYNC:
505 case CSD_TYPE_SYNC:
506 case CSD_TYPE_IRQ_WORK:
507 pr_warn("IPI callback %pS sent to offline CPU\n",
508 csd->func);
509 break;
510
511 case CSD_TYPE_TTWU:
512 pr_warn("IPI task-wakeup sent to offline CPU\n");
513 break;
514
515 default:
516 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n",
517 CSD_TYPE(csd));
518 break;
519 }
520 }
521 }
522
523 /*
524 * First; run all SYNC callbacks, people are waiting for us.
525 */
526 prev = NULL;
527 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) {
528 /* Do we wait until *after* callback? */
529 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) {
530 smp_call_func_t func = csd->func;
531 void *info = csd->info;
532
533 if (prev) {
534 prev->next = &csd_next->node.llist;
535 } else {
536 entry = &csd_next->node.llist;
537 }
538
539 csd_lock_record(csd);
540 csd_do_func(func, info, csd);
541 csd_unlock(csd);
542 csd_lock_record(NULL);
543 } else {
544 prev = &csd->node.llist;
545 }
546 }
547
548 if (!entry)
549 return;
550
551 /*
552 * Second; run all !SYNC callbacks.
553 */
554 prev = NULL;
555 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) {
556 int type = CSD_TYPE(csd);
557
558 if (type != CSD_TYPE_TTWU) {
559 if (prev) {
560 prev->next = &csd_next->node.llist;
561 } else {
562 entry = &csd_next->node.llist;
563 }
564
565 if (type == CSD_TYPE_ASYNC) {
566 smp_call_func_t func = csd->func;
567 void *info = csd->info;
568
569 csd_lock_record(csd);
570 csd_unlock(csd);
571 csd_do_func(func, info, csd);
572 csd_lock_record(NULL);
573 } else if (type == CSD_TYPE_IRQ_WORK) {
574 irq_work_single(csd);
575 }
576
577 } else {
578 prev = &csd->node.llist;
579 }
580 }
581
582 /*
583 * Third; only CSD_TYPE_TTWU is left, issue those.
584 */
585 if (entry) {
586 csd = llist_entry(entry, typeof(*csd), node.llist);
587 csd_do_func(sched_ttwu_pending, entry, csd);
588 }
589}
590
591
592/**
593 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
594 * from task context (idle, migration thread)
595 *
596 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it
597 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by
598 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to
599 * handle queued SMP function calls before scheduling.
600 *
601 * The migration thread has to ensure that an eventually pending wakeup has
602 * been handled before it migrates a task.
603 */
604void flush_smp_call_function_queue(void)
605{
606 unsigned int was_pending;
607 unsigned long flags;
608
609 if (llist_empty(this_cpu_ptr(&call_single_queue)))
610 return;
611
612 local_irq_save(flags);
613 /* Get the already pending soft interrupts for RT enabled kernels */
614 was_pending = local_softirq_pending();
615 __flush_smp_call_function_queue(true);
616 if (local_softirq_pending())
617 do_softirq_post_smp_call_flush(was_pending);
618
619 local_irq_restore(flags);
620}
621
622/*
623 * smp_call_function_single - Run a function on a specific CPU
624 * @func: The function to run. This must be fast and non-blocking.
625 * @info: An arbitrary pointer to pass to the function.
626 * @wait: If true, wait until function has completed on other CPUs.
627 *
628 * Returns 0 on success, else a negative status code.
629 */
630int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
631 int wait)
632{
633 call_single_data_t *csd;
634 call_single_data_t csd_stack = {
635 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, },
636 };
637 int this_cpu;
638 int err;
639
640 /*
641 * prevent preemption and reschedule on another processor,
642 * as well as CPU removal
643 */
644 this_cpu = get_cpu();
645
646 /*
647 * Can deadlock when called with interrupts disabled.
648 * We allow cpu's that are not yet online though, as no one else can
649 * send smp call function interrupt to this cpu and as such deadlocks
650 * can't happen.
651 */
652 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
653 && !oops_in_progress);
654
655 /*
656 * When @wait we can deadlock when we interrupt between llist_add() and
657 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
658 * csd_lock() on because the interrupt context uses the same csd
659 * storage.
660 */
661 WARN_ON_ONCE(!in_task());
662
663 csd = &csd_stack;
664 if (!wait) {
665 csd = this_cpu_ptr(&csd_data);
666 csd_lock(csd);
667 }
668
669 csd->func = func;
670 csd->info = info;
671#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
672 csd->node.src = smp_processor_id();
673 csd->node.dst = cpu;
674#endif
675
676 err = generic_exec_single(cpu, csd);
677
678 if (wait)
679 csd_lock_wait(csd);
680
681 put_cpu();
682
683 return err;
684}
685EXPORT_SYMBOL(smp_call_function_single);
686
687/**
688 * smp_call_function_single_async() - Run an asynchronous function on a
689 * specific CPU.
690 * @cpu: The CPU to run on.
691 * @csd: Pre-allocated and setup data structure
692 *
693 * Like smp_call_function_single(), but the call is asynchonous and
694 * can thus be done from contexts with disabled interrupts.
695 *
696 * The caller passes his own pre-allocated data structure
697 * (ie: embedded in an object) and is responsible for synchronizing it
698 * such that the IPIs performed on the @csd are strictly serialized.
699 *
700 * If the function is called with one csd which has not yet been
701 * processed by previous call to smp_call_function_single_async(), the
702 * function will return immediately with -EBUSY showing that the csd
703 * object is still in progress.
704 *
705 * NOTE: Be careful, there is unfortunately no current debugging facility to
706 * validate the correctness of this serialization.
707 *
708 * Return: %0 on success or negative errno value on error
709 */
710int smp_call_function_single_async(int cpu, call_single_data_t *csd)
711{
712 int err = 0;
713
714 preempt_disable();
715
716 if (csd->node.u_flags & CSD_FLAG_LOCK) {
717 err = -EBUSY;
718 goto out;
719 }
720
721 csd->node.u_flags = CSD_FLAG_LOCK;
722 smp_wmb();
723
724 err = generic_exec_single(cpu, csd);
725
726out:
727 preempt_enable();
728
729 return err;
730}
731EXPORT_SYMBOL_GPL(smp_call_function_single_async);
732
733/*
734 * smp_call_function_any - Run a function on any of the given cpus
735 * @mask: The mask of cpus it can run on.
736 * @func: The function to run. This must be fast and non-blocking.
737 * @info: An arbitrary pointer to pass to the function.
738 * @wait: If true, wait until function has completed.
739 *
740 * Returns 0 on success, else a negative status code (if no cpus were online).
741 *
742 * Selection preference:
743 * 1) current cpu if in @mask
744 * 2) any cpu of current node if in @mask
745 * 3) any other online cpu in @mask
746 */
747int smp_call_function_any(const struct cpumask *mask,
748 smp_call_func_t func, void *info, int wait)
749{
750 unsigned int cpu;
751 const struct cpumask *nodemask;
752 int ret;
753
754 /* Try for same CPU (cheapest) */
755 cpu = get_cpu();
756 if (cpumask_test_cpu(cpu, mask))
757 goto call;
758
759 /* Try for same node. */
760 nodemask = cpumask_of_node(cpu_to_node(cpu));
761 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
762 cpu = cpumask_next_and(cpu, nodemask, mask)) {
763 if (cpu_online(cpu))
764 goto call;
765 }
766
767 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
768 cpu = cpumask_any_and(mask, cpu_online_mask);
769call:
770 ret = smp_call_function_single(cpu, func, info, wait);
771 put_cpu();
772 return ret;
773}
774EXPORT_SYMBOL_GPL(smp_call_function_any);
775
776/*
777 * Flags to be used as scf_flags argument of smp_call_function_many_cond().
778 *
779 * %SCF_WAIT: Wait until function execution is completed
780 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask
781 */
782#define SCF_WAIT (1U << 0)
783#define SCF_RUN_LOCAL (1U << 1)
784
785static void smp_call_function_many_cond(const struct cpumask *mask,
786 smp_call_func_t func, void *info,
787 unsigned int scf_flags,
788 smp_cond_func_t cond_func)
789{
790 int cpu, last_cpu, this_cpu = smp_processor_id();
791 struct call_function_data *cfd;
792 bool wait = scf_flags & SCF_WAIT;
793 int nr_cpus = 0;
794 bool run_remote = false;
795 bool run_local = false;
796
797 lockdep_assert_preemption_disabled();
798
799 /*
800 * Can deadlock when called with interrupts disabled.
801 * We allow cpu's that are not yet online though, as no one else can
802 * send smp call function interrupt to this cpu and as such deadlocks
803 * can't happen.
804 */
805 if (cpu_online(this_cpu) && !oops_in_progress &&
806 !early_boot_irqs_disabled)
807 lockdep_assert_irqs_enabled();
808
809 /*
810 * When @wait we can deadlock when we interrupt between llist_add() and
811 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
812 * csd_lock() on because the interrupt context uses the same csd
813 * storage.
814 */
815 WARN_ON_ONCE(!in_task());
816
817 /* Check if we need local execution. */
818 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask))
819 run_local = true;
820
821 /* Check if we need remote execution, i.e., any CPU excluding this one. */
822 cpu = cpumask_first_and(mask, cpu_online_mask);
823 if (cpu == this_cpu)
824 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
825 if (cpu < nr_cpu_ids)
826 run_remote = true;
827
828 if (run_remote) {
829 cfd = this_cpu_ptr(&cfd_data);
830 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
831 __cpumask_clear_cpu(this_cpu, cfd->cpumask);
832
833 cpumask_clear(cfd->cpumask_ipi);
834 for_each_cpu(cpu, cfd->cpumask) {
835 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
836
837 if (cond_func && !cond_func(cpu, info)) {
838 __cpumask_clear_cpu(cpu, cfd->cpumask);
839 continue;
840 }
841
842 csd_lock(csd);
843 if (wait)
844 csd->node.u_flags |= CSD_TYPE_SYNC;
845 csd->func = func;
846 csd->info = info;
847#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
848 csd->node.src = smp_processor_id();
849 csd->node.dst = cpu;
850#endif
851 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
852
853 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {
854 __cpumask_set_cpu(cpu, cfd->cpumask_ipi);
855 nr_cpus++;
856 last_cpu = cpu;
857 }
858 }
859
860 /*
861 * Choose the most efficient way to send an IPI. Note that the
862 * number of CPUs might be zero due to concurrent changes to the
863 * provided mask.
864 */
865 if (nr_cpus == 1)
866 send_call_function_single_ipi(last_cpu);
867 else if (likely(nr_cpus > 1))
868 send_call_function_ipi_mask(cfd->cpumask_ipi);
869 }
870
871 if (run_local && (!cond_func || cond_func(this_cpu, info))) {
872 unsigned long flags;
873
874 local_irq_save(flags);
875 csd_do_func(func, info, NULL);
876 local_irq_restore(flags);
877 }
878
879 if (run_remote && wait) {
880 for_each_cpu(cpu, cfd->cpumask) {
881 call_single_data_t *csd;
882
883 csd = per_cpu_ptr(cfd->csd, cpu);
884 csd_lock_wait(csd);
885 }
886 }
887}
888
889/**
890 * smp_call_function_many(): Run a function on a set of CPUs.
891 * @mask: The set of cpus to run on (only runs on online subset).
892 * @func: The function to run. This must be fast and non-blocking.
893 * @info: An arbitrary pointer to pass to the function.
894 * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait
895 * (atomically) until function has completed on other CPUs. If
896 * %SCF_RUN_LOCAL is set, the function will also be run locally
897 * if the local CPU is set in the @cpumask.
898 *
899 * If @wait is true, then returns once @func has returned.
900 *
901 * You must not call this function with disabled interrupts or from a
902 * hardware interrupt handler or from a bottom half handler. Preemption
903 * must be disabled when calling this function.
904 */
905void smp_call_function_many(const struct cpumask *mask,
906 smp_call_func_t func, void *info, bool wait)
907{
908 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL);
909}
910EXPORT_SYMBOL(smp_call_function_many);
911
912/**
913 * smp_call_function(): Run a function on all other CPUs.
914 * @func: The function to run. This must be fast and non-blocking.
915 * @info: An arbitrary pointer to pass to the function.
916 * @wait: If true, wait (atomically) until function has completed
917 * on other CPUs.
918 *
919 * Returns 0.
920 *
921 * If @wait is true, then returns once @func has returned; otherwise
922 * it returns just before the target cpu calls @func.
923 *
924 * You must not call this function with disabled interrupts or from a
925 * hardware interrupt handler or from a bottom half handler.
926 */
927void smp_call_function(smp_call_func_t func, void *info, int wait)
928{
929 preempt_disable();
930 smp_call_function_many(cpu_online_mask, func, info, wait);
931 preempt_enable();
932}
933EXPORT_SYMBOL(smp_call_function);
934
935/* Setup configured maximum number of CPUs to activate */
936unsigned int setup_max_cpus = NR_CPUS;
937EXPORT_SYMBOL(setup_max_cpus);
938
939
940/*
941 * Setup routine for controlling SMP activation
942 *
943 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
944 * activation entirely (the MPS table probe still happens, though).
945 *
946 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
947 * greater than 0, limits the maximum number of CPUs activated in
948 * SMP mode to <NUM>.
949 */
950
951void __weak __init arch_disable_smp_support(void) { }
952
953static int __init nosmp(char *str)
954{
955 setup_max_cpus = 0;
956 arch_disable_smp_support();
957
958 return 0;
959}
960
961early_param("nosmp", nosmp);
962
963/* this is hard limit */
964static int __init nrcpus(char *str)
965{
966 int nr_cpus;
967
968 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids)
969 set_nr_cpu_ids(nr_cpus);
970
971 return 0;
972}
973
974early_param("nr_cpus", nrcpus);
975
976static int __init maxcpus(char *str)
977{
978 get_option(&str, &setup_max_cpus);
979 if (setup_max_cpus == 0)
980 arch_disable_smp_support();
981
982 return 0;
983}
984
985early_param("maxcpus", maxcpus);
986
987#if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS)
988/* Setup number of possible processor ids */
989unsigned int nr_cpu_ids __read_mostly = NR_CPUS;
990EXPORT_SYMBOL(nr_cpu_ids);
991#endif
992
993/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
994void __init setup_nr_cpu_ids(void)
995{
996 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1);
997}
998
999/* Called by boot processor to activate the rest. */
1000void __init smp_init(void)
1001{
1002 int num_nodes, num_cpus;
1003
1004 idle_threads_init();
1005 cpuhp_threads_init();
1006
1007 pr_info("Bringing up secondary CPUs ...\n");
1008
1009 bringup_nonboot_cpus(setup_max_cpus);
1010
1011 num_nodes = num_online_nodes();
1012 num_cpus = num_online_cpus();
1013 pr_info("Brought up %d node%s, %d CPU%s\n",
1014 num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus));
1015
1016 /* Any cleanup work */
1017 smp_cpus_done(setup_max_cpus);
1018}
1019
1020/*
1021 * on_each_cpu_cond(): Call a function on each processor for which
1022 * the supplied function cond_func returns true, optionally waiting
1023 * for all the required CPUs to finish. This may include the local
1024 * processor.
1025 * @cond_func: A callback function that is passed a cpu id and
1026 * the info parameter. The function is called
1027 * with preemption disabled. The function should
1028 * return a blooean value indicating whether to IPI
1029 * the specified CPU.
1030 * @func: The function to run on all applicable CPUs.
1031 * This must be fast and non-blocking.
1032 * @info: An arbitrary pointer to pass to both functions.
1033 * @wait: If true, wait (atomically) until function has
1034 * completed on other CPUs.
1035 *
1036 * Preemption is disabled to protect against CPUs going offline but not online.
1037 * CPUs going online during the call will not be seen or sent an IPI.
1038 *
1039 * You must not call this function with disabled interrupts or
1040 * from a hardware interrupt handler or from a bottom half handler.
1041 */
1042void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
1043 void *info, bool wait, const struct cpumask *mask)
1044{
1045 unsigned int scf_flags = SCF_RUN_LOCAL;
1046
1047 if (wait)
1048 scf_flags |= SCF_WAIT;
1049
1050 preempt_disable();
1051 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func);
1052 preempt_enable();
1053}
1054EXPORT_SYMBOL(on_each_cpu_cond_mask);
1055
1056static void do_nothing(void *unused)
1057{
1058}
1059
1060/**
1061 * kick_all_cpus_sync - Force all cpus out of idle
1062 *
1063 * Used to synchronize the update of pm_idle function pointer. It's
1064 * called after the pointer is updated and returns after the dummy
1065 * callback function has been executed on all cpus. The execution of
1066 * the function can only happen on the remote cpus after they have
1067 * left the idle function which had been called via pm_idle function
1068 * pointer. So it's guaranteed that nothing uses the previous pointer
1069 * anymore.
1070 */
1071void kick_all_cpus_sync(void)
1072{
1073 /* Make sure the change is visible before we kick the cpus */
1074 smp_mb();
1075 smp_call_function(do_nothing, NULL, 1);
1076}
1077EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
1078
1079/**
1080 * wake_up_all_idle_cpus - break all cpus out of idle
1081 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
1082 * including idle polling cpus, for non-idle cpus, we will do nothing
1083 * for them.
1084 */
1085void wake_up_all_idle_cpus(void)
1086{
1087 int cpu;
1088
1089 for_each_possible_cpu(cpu) {
1090 preempt_disable();
1091 if (cpu != smp_processor_id() && cpu_online(cpu))
1092 wake_up_if_idle(cpu);
1093 preempt_enable();
1094 }
1095}
1096EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
1097
1098/**
1099 * struct smp_call_on_cpu_struct - Call a function on a specific CPU
1100 * @work: &work_struct
1101 * @done: &completion to signal
1102 * @func: function to call
1103 * @data: function's data argument
1104 * @ret: return value from @func
1105 * @cpu: target CPU (%-1 for any CPU)
1106 *
1107 * Used to call a function on a specific cpu and wait for it to return.
1108 * Optionally make sure the call is done on a specified physical cpu via vcpu
1109 * pinning in order to support virtualized environments.
1110 */
1111struct smp_call_on_cpu_struct {
1112 struct work_struct work;
1113 struct completion done;
1114 int (*func)(void *);
1115 void *data;
1116 int ret;
1117 int cpu;
1118};
1119
1120static void smp_call_on_cpu_callback(struct work_struct *work)
1121{
1122 struct smp_call_on_cpu_struct *sscs;
1123
1124 sscs = container_of(work, struct smp_call_on_cpu_struct, work);
1125 if (sscs->cpu >= 0)
1126 hypervisor_pin_vcpu(sscs->cpu);
1127 sscs->ret = sscs->func(sscs->data);
1128 if (sscs->cpu >= 0)
1129 hypervisor_pin_vcpu(-1);
1130
1131 complete(&sscs->done);
1132}
1133
1134int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
1135{
1136 struct smp_call_on_cpu_struct sscs = {
1137 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
1138 .func = func,
1139 .data = par,
1140 .cpu = phys ? cpu : -1,
1141 };
1142
1143 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
1144
1145 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
1146 return -ENXIO;
1147
1148 queue_work_on(cpu, system_wq, &sscs.work);
1149 wait_for_completion(&sscs.done);
1150 destroy_work_on_stack(&sscs.work);
1151
1152 return sscs.ret;
1153}
1154EXPORT_SYMBOL_GPL(smp_call_on_cpu);