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