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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/irq_work.h>
7 #include <linux/rcupdate.h>
8 #include <linux/rculist.h>
9 #include <linux/kernel.h>
10 #include <linux/export.h>
11 #include <linux/percpu.h>
12 #include <linux/init.h>
13 #include <linux/gfp.h>
14 #include <linux/smp.h>
15 #include <linux/cpu.h>
16 #include <linux/sched.h>
17
18 #include "smpboot.h"
19
20 enum {
21 CSD_FLAG_LOCK = 0x01,
22 CSD_FLAG_SYNCHRONOUS = 0x02,
23 };
24
25 struct call_function_data {
26 struct call_single_data __percpu *csd;
27 cpumask_var_t cpumask;
28 };
29
30 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
31
32 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
33
34 static void flush_smp_call_function_queue(bool warn_cpu_offline);
35
36 int smpcfd_prepare_cpu(unsigned int cpu)
37 {
38 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
39
40 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
41 cpu_to_node(cpu)))
42 return -ENOMEM;
43 cfd->csd = alloc_percpu(struct call_single_data);
44 if (!cfd->csd) {
45 free_cpumask_var(cfd->cpumask);
46 return -ENOMEM;
47 }
48
49 return 0;
50 }
51
52 int smpcfd_dead_cpu(unsigned int cpu)
53 {
54 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
55
56 free_cpumask_var(cfd->cpumask);
57 free_percpu(cfd->csd);
58 return 0;
59 }
60
61 int smpcfd_dying_cpu(unsigned int cpu)
62 {
63 /*
64 * The IPIs for the smp-call-function callbacks queued by other
65 * CPUs might arrive late, either due to hardware latencies or
66 * because this CPU disabled interrupts (inside stop-machine)
67 * before the IPIs were sent. So flush out any pending callbacks
68 * explicitly (without waiting for the IPIs to arrive), to
69 * ensure that the outgoing CPU doesn't go offline with work
70 * still pending.
71 */
72 flush_smp_call_function_queue(false);
73 return 0;
74 }
75
76 void __init call_function_init(void)
77 {
78 int i;
79
80 for_each_possible_cpu(i)
81 init_llist_head(&per_cpu(call_single_queue, i));
82
83 smpcfd_prepare_cpu(smp_processor_id());
84 }
85
86 /*
87 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
88 *
89 * For non-synchronous ipi calls the csd can still be in use by the
90 * previous function call. For multi-cpu calls its even more interesting
91 * as we'll have to ensure no other cpu is observing our csd.
92 */
93 static __always_inline void csd_lock_wait(struct call_single_data *csd)
94 {
95 smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
96 }
97
98 static __always_inline void csd_lock(struct call_single_data *csd)
99 {
100 csd_lock_wait(csd);
101 csd->flags |= CSD_FLAG_LOCK;
102
103 /*
104 * prevent CPU from reordering the above assignment
105 * to ->flags with any subsequent assignments to other
106 * fields of the specified call_single_data structure:
107 */
108 smp_wmb();
109 }
110
111 static __always_inline void csd_unlock(struct call_single_data *csd)
112 {
113 WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
114
115 /*
116 * ensure we're all done before releasing data:
117 */
118 smp_store_release(&csd->flags, 0);
119 }
120
121 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
122
123 /*
124 * Insert a previously allocated call_single_data element
125 * for execution on the given CPU. data must already have
126 * ->func, ->info, and ->flags set.
127 */
128 static int generic_exec_single(int cpu, struct call_single_data *csd,
129 smp_call_func_t func, void *info)
130 {
131 if (cpu == smp_processor_id()) {
132 unsigned long flags;
133
134 /*
135 * We can unlock early even for the synchronous on-stack case,
136 * since we're doing this from the same CPU..
137 */
138 csd_unlock(csd);
139 local_irq_save(flags);
140 func(info);
141 local_irq_restore(flags);
142 return 0;
143 }
144
145
146 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
147 csd_unlock(csd);
148 return -ENXIO;
149 }
150
151 csd->func = func;
152 csd->info = info;
153
154 /*
155 * The list addition should be visible before sending the IPI
156 * handler locks the list to pull the entry off it because of
157 * normal cache coherency rules implied by spinlocks.
158 *
159 * If IPIs can go out of order to the cache coherency protocol
160 * in an architecture, sufficient synchronisation should be added
161 * to arch code to make it appear to obey cache coherency WRT
162 * locking and barrier primitives. Generic code isn't really
163 * equipped to do the right thing...
164 */
165 if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
166 arch_send_call_function_single_ipi(cpu);
167
168 return 0;
169 }
170
171 /**
172 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
173 *
174 * Invoked by arch to handle an IPI for call function single.
175 * Must be called with interrupts disabled.
176 */
177 void generic_smp_call_function_single_interrupt(void)
178 {
179 flush_smp_call_function_queue(true);
180 }
181
182 /**
183 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
184 *
185 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
186 * offline CPU. Skip this check if set to 'false'.
187 *
188 * Flush any pending smp-call-function callbacks queued on this CPU. This is
189 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
190 * to ensure that all pending IPI callbacks are run before it goes completely
191 * offline.
192 *
193 * Loop through the call_single_queue and run all the queued callbacks.
194 * Must be called with interrupts disabled.
195 */
196 static void flush_smp_call_function_queue(bool warn_cpu_offline)
197 {
198 struct llist_head *head;
199 struct llist_node *entry;
200 struct call_single_data *csd, *csd_next;
201 static bool warned;
202
203 WARN_ON(!irqs_disabled());
204
205 head = this_cpu_ptr(&call_single_queue);
206 entry = llist_del_all(head);
207 entry = llist_reverse_order(entry);
208
209 /* There shouldn't be any pending callbacks on an offline CPU. */
210 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
211 !warned && !llist_empty(head))) {
212 warned = true;
213 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
214
215 /*
216 * We don't have to use the _safe() variant here
217 * because we are not invoking the IPI handlers yet.
218 */
219 llist_for_each_entry(csd, entry, llist)
220 pr_warn("IPI callback %pS sent to offline CPU\n",
221 csd->func);
222 }
223
224 llist_for_each_entry_safe(csd, csd_next, entry, llist) {
225 smp_call_func_t func = csd->func;
226 void *info = csd->info;
227
228 /* Do we wait until *after* callback? */
229 if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
230 func(info);
231 csd_unlock(csd);
232 } else {
233 csd_unlock(csd);
234 func(info);
235 }
236 }
237
238 /*
239 * Handle irq works queued remotely by irq_work_queue_on().
240 * Smp functions above are typically synchronous so they
241 * better run first since some other CPUs may be busy waiting
242 * for them.
243 */
244 irq_work_run();
245 }
246
247 /*
248 * smp_call_function_single - Run a function on a specific CPU
249 * @func: The function to run. This must be fast and non-blocking.
250 * @info: An arbitrary pointer to pass to the function.
251 * @wait: If true, wait until function has completed on other CPUs.
252 *
253 * Returns 0 on success, else a negative status code.
254 */
255 int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
256 int wait)
257 {
258 struct call_single_data *csd;
259 struct call_single_data csd_stack = { .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS };
260 int this_cpu;
261 int err;
262
263 /*
264 * prevent preemption and reschedule on another processor,
265 * as well as CPU removal
266 */
267 this_cpu = get_cpu();
268
269 /*
270 * Can deadlock when called with interrupts disabled.
271 * We allow cpu's that are not yet online though, as no one else can
272 * send smp call function interrupt to this cpu and as such deadlocks
273 * can't happen.
274 */
275 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
276 && !oops_in_progress);
277
278 csd = &csd_stack;
279 if (!wait) {
280 csd = this_cpu_ptr(&csd_data);
281 csd_lock(csd);
282 }
283
284 err = generic_exec_single(cpu, csd, func, info);
285
286 if (wait)
287 csd_lock_wait(csd);
288
289 put_cpu();
290
291 return err;
292 }
293 EXPORT_SYMBOL(smp_call_function_single);
294
295 /**
296 * smp_call_function_single_async(): Run an asynchronous function on a
297 * specific CPU.
298 * @cpu: The CPU to run on.
299 * @csd: Pre-allocated and setup data structure
300 *
301 * Like smp_call_function_single(), but the call is asynchonous and
302 * can thus be done from contexts with disabled interrupts.
303 *
304 * The caller passes his own pre-allocated data structure
305 * (ie: embedded in an object) and is responsible for synchronizing it
306 * such that the IPIs performed on the @csd are strictly serialized.
307 *
308 * NOTE: Be careful, there is unfortunately no current debugging facility to
309 * validate the correctness of this serialization.
310 */
311 int smp_call_function_single_async(int cpu, struct call_single_data *csd)
312 {
313 int err = 0;
314
315 preempt_disable();
316
317 /* We could deadlock if we have to wait here with interrupts disabled! */
318 if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
319 csd_lock_wait(csd);
320
321 csd->flags = CSD_FLAG_LOCK;
322 smp_wmb();
323
324 err = generic_exec_single(cpu, csd, csd->func, csd->info);
325 preempt_enable();
326
327 return err;
328 }
329 EXPORT_SYMBOL_GPL(smp_call_function_single_async);
330
331 /*
332 * smp_call_function_any - Run a function on any of the given cpus
333 * @mask: The mask of cpus it can run on.
334 * @func: The function to run. This must be fast and non-blocking.
335 * @info: An arbitrary pointer to pass to the function.
336 * @wait: If true, wait until function has completed.
337 *
338 * Returns 0 on success, else a negative status code (if no cpus were online).
339 *
340 * Selection preference:
341 * 1) current cpu if in @mask
342 * 2) any cpu of current node if in @mask
343 * 3) any other online cpu in @mask
344 */
345 int smp_call_function_any(const struct cpumask *mask,
346 smp_call_func_t func, void *info, int wait)
347 {
348 unsigned int cpu;
349 const struct cpumask *nodemask;
350 int ret;
351
352 /* Try for same CPU (cheapest) */
353 cpu = get_cpu();
354 if (cpumask_test_cpu(cpu, mask))
355 goto call;
356
357 /* Try for same node. */
358 nodemask = cpumask_of_node(cpu_to_node(cpu));
359 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
360 cpu = cpumask_next_and(cpu, nodemask, mask)) {
361 if (cpu_online(cpu))
362 goto call;
363 }
364
365 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
366 cpu = cpumask_any_and(mask, cpu_online_mask);
367 call:
368 ret = smp_call_function_single(cpu, func, info, wait);
369 put_cpu();
370 return ret;
371 }
372 EXPORT_SYMBOL_GPL(smp_call_function_any);
373
374 /**
375 * smp_call_function_many(): Run a function on a set of other CPUs.
376 * @mask: The set of cpus to run on (only runs on online subset).
377 * @func: The function to run. This must be fast and non-blocking.
378 * @info: An arbitrary pointer to pass to the function.
379 * @wait: If true, wait (atomically) until function has completed
380 * on other CPUs.
381 *
382 * If @wait is true, then returns once @func has returned.
383 *
384 * You must not call this function with disabled interrupts or from a
385 * hardware interrupt handler or from a bottom half handler. Preemption
386 * must be disabled when calling this function.
387 */
388 void smp_call_function_many(const struct cpumask *mask,
389 smp_call_func_t func, void *info, bool wait)
390 {
391 struct call_function_data *cfd;
392 int cpu, next_cpu, this_cpu = smp_processor_id();
393
394 /*
395 * Can deadlock when called with interrupts disabled.
396 * We allow cpu's that are not yet online though, as no one else can
397 * send smp call function interrupt to this cpu and as such deadlocks
398 * can't happen.
399 */
400 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
401 && !oops_in_progress && !early_boot_irqs_disabled);
402
403 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
404 cpu = cpumask_first_and(mask, cpu_online_mask);
405 if (cpu == this_cpu)
406 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
407
408 /* No online cpus? We're done. */
409 if (cpu >= nr_cpu_ids)
410 return;
411
412 /* Do we have another CPU which isn't us? */
413 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
414 if (next_cpu == this_cpu)
415 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
416
417 /* Fastpath: do that cpu by itself. */
418 if (next_cpu >= nr_cpu_ids) {
419 smp_call_function_single(cpu, func, info, wait);
420 return;
421 }
422
423 cfd = this_cpu_ptr(&cfd_data);
424
425 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
426 cpumask_clear_cpu(this_cpu, cfd->cpumask);
427
428 /* Some callers race with other cpus changing the passed mask */
429 if (unlikely(!cpumask_weight(cfd->cpumask)))
430 return;
431
432 for_each_cpu(cpu, cfd->cpumask) {
433 struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
434
435 csd_lock(csd);
436 if (wait)
437 csd->flags |= CSD_FLAG_SYNCHRONOUS;
438 csd->func = func;
439 csd->info = info;
440 llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
441 }
442
443 /* Send a message to all CPUs in the map */
444 arch_send_call_function_ipi_mask(cfd->cpumask);
445
446 if (wait) {
447 for_each_cpu(cpu, cfd->cpumask) {
448 struct call_single_data *csd;
449
450 csd = per_cpu_ptr(cfd->csd, cpu);
451 csd_lock_wait(csd);
452 }
453 }
454 }
455 EXPORT_SYMBOL(smp_call_function_many);
456
457 /**
458 * smp_call_function(): Run a function on all other CPUs.
459 * @func: The function to run. This must be fast and non-blocking.
460 * @info: An arbitrary pointer to pass to the function.
461 * @wait: If true, wait (atomically) until function has completed
462 * on other CPUs.
463 *
464 * Returns 0.
465 *
466 * If @wait is true, then returns once @func has returned; otherwise
467 * it returns just before the target cpu calls @func.
468 *
469 * You must not call this function with disabled interrupts or from a
470 * hardware interrupt handler or from a bottom half handler.
471 */
472 int smp_call_function(smp_call_func_t func, void *info, int wait)
473 {
474 preempt_disable();
475 smp_call_function_many(cpu_online_mask, func, info, wait);
476 preempt_enable();
477
478 return 0;
479 }
480 EXPORT_SYMBOL(smp_call_function);
481
482 /* Setup configured maximum number of CPUs to activate */
483 unsigned int setup_max_cpus = NR_CPUS;
484 EXPORT_SYMBOL(setup_max_cpus);
485
486
487 /*
488 * Setup routine for controlling SMP activation
489 *
490 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
491 * activation entirely (the MPS table probe still happens, though).
492 *
493 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
494 * greater than 0, limits the maximum number of CPUs activated in
495 * SMP mode to <NUM>.
496 */
497
498 void __weak arch_disable_smp_support(void) { }
499
500 static int __init nosmp(char *str)
501 {
502 setup_max_cpus = 0;
503 arch_disable_smp_support();
504
505 return 0;
506 }
507
508 early_param("nosmp", nosmp);
509
510 /* this is hard limit */
511 static int __init nrcpus(char *str)
512 {
513 int nr_cpus;
514
515 get_option(&str, &nr_cpus);
516 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
517 nr_cpu_ids = nr_cpus;
518
519 return 0;
520 }
521
522 early_param("nr_cpus", nrcpus);
523
524 static int __init maxcpus(char *str)
525 {
526 get_option(&str, &setup_max_cpus);
527 if (setup_max_cpus == 0)
528 arch_disable_smp_support();
529
530 return 0;
531 }
532
533 early_param("maxcpus", maxcpus);
534
535 /* Setup number of possible processor ids */
536 int nr_cpu_ids __read_mostly = NR_CPUS;
537 EXPORT_SYMBOL(nr_cpu_ids);
538
539 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
540 void __init setup_nr_cpu_ids(void)
541 {
542 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
543 }
544
545 void __weak smp_announce(void)
546 {
547 printk(KERN_INFO "Brought up %d CPUs\n", num_online_cpus());
548 }
549
550 /* Called by boot processor to activate the rest. */
551 void __init smp_init(void)
552 {
553 unsigned int cpu;
554
555 idle_threads_init();
556 cpuhp_threads_init();
557
558 /* FIXME: This should be done in userspace --RR */
559 for_each_present_cpu(cpu) {
560 if (num_online_cpus() >= setup_max_cpus)
561 break;
562 if (!cpu_online(cpu))
563 cpu_up(cpu);
564 }
565
566 /* Any cleanup work */
567 smp_announce();
568 smp_cpus_done(setup_max_cpus);
569 }
570
571 /*
572 * Call a function on all processors. May be used during early boot while
573 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
574 * of local_irq_disable/enable().
575 */
576 int on_each_cpu(void (*func) (void *info), void *info, int wait)
577 {
578 unsigned long flags;
579 int ret = 0;
580
581 preempt_disable();
582 ret = smp_call_function(func, info, wait);
583 local_irq_save(flags);
584 func(info);
585 local_irq_restore(flags);
586 preempt_enable();
587 return ret;
588 }
589 EXPORT_SYMBOL(on_each_cpu);
590
591 /**
592 * on_each_cpu_mask(): Run a function on processors specified by
593 * cpumask, which may include the local processor.
594 * @mask: The set of cpus to run on (only runs on online subset).
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 (atomically) until function has completed
598 * on other CPUs.
599 *
600 * If @wait is true, then returns once @func has returned.
601 *
602 * You must not call this function with disabled interrupts or from a
603 * hardware interrupt handler or from a bottom half handler. The
604 * exception is that it may be used during early boot while
605 * early_boot_irqs_disabled is set.
606 */
607 void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
608 void *info, bool wait)
609 {
610 int cpu = get_cpu();
611
612 smp_call_function_many(mask, func, info, wait);
613 if (cpumask_test_cpu(cpu, mask)) {
614 unsigned long flags;
615 local_irq_save(flags);
616 func(info);
617 local_irq_restore(flags);
618 }
619 put_cpu();
620 }
621 EXPORT_SYMBOL(on_each_cpu_mask);
622
623 /*
624 * on_each_cpu_cond(): Call a function on each processor for which
625 * the supplied function cond_func returns true, optionally waiting
626 * for all the required CPUs to finish. This may include the local
627 * processor.
628 * @cond_func: A callback function that is passed a cpu id and
629 * the the info parameter. The function is called
630 * with preemption disabled. The function should
631 * return a blooean value indicating whether to IPI
632 * the specified CPU.
633 * @func: The function to run on all applicable CPUs.
634 * This must be fast and non-blocking.
635 * @info: An arbitrary pointer to pass to both functions.
636 * @wait: If true, wait (atomically) until function has
637 * completed on other CPUs.
638 * @gfp_flags: GFP flags to use when allocating the cpumask
639 * used internally by the function.
640 *
641 * The function might sleep if the GFP flags indicates a non
642 * atomic allocation is allowed.
643 *
644 * Preemption is disabled to protect against CPUs going offline but not online.
645 * CPUs going online during the call will not be seen or sent an IPI.
646 *
647 * You must not call this function with disabled interrupts or
648 * from a hardware interrupt handler or from a bottom half handler.
649 */
650 void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
651 smp_call_func_t func, void *info, bool wait,
652 gfp_t gfp_flags)
653 {
654 cpumask_var_t cpus;
655 int cpu, ret;
656
657 might_sleep_if(gfpflags_allow_blocking(gfp_flags));
658
659 if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
660 preempt_disable();
661 for_each_online_cpu(cpu)
662 if (cond_func(cpu, info))
663 cpumask_set_cpu(cpu, cpus);
664 on_each_cpu_mask(cpus, func, info, wait);
665 preempt_enable();
666 free_cpumask_var(cpus);
667 } else {
668 /*
669 * No free cpumask, bother. No matter, we'll
670 * just have to IPI them one by one.
671 */
672 preempt_disable();
673 for_each_online_cpu(cpu)
674 if (cond_func(cpu, info)) {
675 ret = smp_call_function_single(cpu, func,
676 info, wait);
677 WARN_ON_ONCE(ret);
678 }
679 preempt_enable();
680 }
681 }
682 EXPORT_SYMBOL(on_each_cpu_cond);
683
684 static void do_nothing(void *unused)
685 {
686 }
687
688 /**
689 * kick_all_cpus_sync - Force all cpus out of idle
690 *
691 * Used to synchronize the update of pm_idle function pointer. It's
692 * called after the pointer is updated and returns after the dummy
693 * callback function has been executed on all cpus. The execution of
694 * the function can only happen on the remote cpus after they have
695 * left the idle function which had been called via pm_idle function
696 * pointer. So it's guaranteed that nothing uses the previous pointer
697 * anymore.
698 */
699 void kick_all_cpus_sync(void)
700 {
701 /* Make sure the change is visible before we kick the cpus */
702 smp_mb();
703 smp_call_function(do_nothing, NULL, 1);
704 }
705 EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
706
707 /**
708 * wake_up_all_idle_cpus - break all cpus out of idle
709 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
710 * including idle polling cpus, for non-idle cpus, we will do nothing
711 * for them.
712 */
713 void wake_up_all_idle_cpus(void)
714 {
715 int cpu;
716
717 preempt_disable();
718 for_each_online_cpu(cpu) {
719 if (cpu == smp_processor_id())
720 continue;
721
722 wake_up_if_idle(cpu);
723 }
724 preempt_enable();
725 }
726 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);