Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/kernel/smp.c

  1 /*
  2  * Generic helpers for smp ipi calls
  3  *
  4  * (C) Jens Axboe <jens.axboe@oracle.com> 2008
  5  */
  6 
  7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8 
  9 #include <linux/irq_work.h>
 10 #include <linux/rcupdate.h>
 11 #include <linux/rculist.h>
 12 #include <linux/kernel.h>
 13 #include <linux/export.h>
 14 #include <linux/percpu.h>
 15 #include <linux/init.h>
 16 #include <linux/gfp.h>
 17 #include <linux/smp.h>
 18 #include <linux/cpu.h>
 19 #include <linux/sched.h>
 20 #include <linux/hypervisor.h>
 21 
 22 #include "smpboot.h"
 23 
 24 enum {
 25         CSD_FLAG_LOCK           = 0x01,
 26         CSD_FLAG_SYNCHRONOUS    = 0x02,
 27 };
 28 
 29 struct call_function_data {
 30         struct call_single_data __percpu *csd;
 31         cpumask_var_t           cpumask;
 32 };
 33 
 34 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
 35 
 36 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
 37 
 38 static void flush_smp_call_function_queue(bool warn_cpu_offline);
 39 
 40 int smpcfd_prepare_cpu(unsigned int cpu)
 41 {
 42         struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
 43 
 44         if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
 45                                      cpu_to_node(cpu)))
 46                 return -ENOMEM;
 47         cfd->csd = alloc_percpu(struct call_single_data);
 48         if (!cfd->csd) {
 49                 free_cpumask_var(cfd->cpumask);
 50                 return -ENOMEM;
 51         }
 52 
 53         return 0;
 54 }
 55 
 56 int smpcfd_dead_cpu(unsigned int cpu)
 57 {
 58         struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
 59 
 60         free_cpumask_var(cfd->cpumask);
 61         free_percpu(cfd->csd);
 62         return 0;
 63 }
 64 
 65 int smpcfd_dying_cpu(unsigned int cpu)
 66 {
 67         /*
 68          * The IPIs for the smp-call-function callbacks queued by other
 69          * CPUs might arrive late, either due to hardware latencies or
 70          * because this CPU disabled interrupts (inside stop-machine)
 71          * before the IPIs were sent. So flush out any pending callbacks
 72          * explicitly (without waiting for the IPIs to arrive), to
 73          * ensure that the outgoing CPU doesn't go offline with work
 74          * still pending.
 75          */
 76         flush_smp_call_function_queue(false);
 77         return 0;
 78 }
 79 
 80 void __init call_function_init(void)
 81 {
 82         int i;
 83 
 84         for_each_possible_cpu(i)
 85                 init_llist_head(&per_cpu(call_single_queue, i));
 86 
 87         smpcfd_prepare_cpu(smp_processor_id());
 88 }
 89 
 90 /*
 91  * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
 92  *
 93  * For non-synchronous ipi calls the csd can still be in use by the
 94  * previous function call. For multi-cpu calls its even more interesting
 95  * as we'll have to ensure no other cpu is observing our csd.
 96  */
 97 static __always_inline void csd_lock_wait(struct call_single_data *csd)
 98 {
 99         smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
100 }
101 
102 static __always_inline void csd_lock(struct call_single_data *csd)
103 {
104         csd_lock_wait(csd);
105         csd->flags |= CSD_FLAG_LOCK;
106 
107         /*
108          * prevent CPU from reordering the above assignment
109          * to ->flags with any subsequent assignments to other
110          * fields of the specified call_single_data structure:
111          */
112         smp_wmb();
113 }
114 
115 static __always_inline void csd_unlock(struct call_single_data *csd)
116 {
117         WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
118 
119         /*
120          * ensure we're all done before releasing data:
121          */
122         smp_store_release(&csd->flags, 0);
123 }
124 
125 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
126 
127 /*
128  * Insert a previously allocated call_single_data element
129  * for execution on the given CPU. data must already have
130  * ->func, ->info, and ->flags set.
131  */
132 static int generic_exec_single(int cpu, struct call_single_data *csd,
133                                smp_call_func_t func, void *info)
134 {
135         if (cpu == smp_processor_id()) {
136                 unsigned long flags;
137 
138                 /*
139                  * We can unlock early even for the synchronous on-stack case,
140                  * since we're doing this from the same CPU..
141                  */
142                 csd_unlock(csd);
143                 local_irq_save(flags);
144                 func(info);
145                 local_irq_restore(flags);
146                 return 0;
147         }
148 
149 
150         if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
151                 csd_unlock(csd);
152                 return -ENXIO;
153         }
154 
155         csd->func = func;
156         csd->info = info;
157 
158         /*
159          * The list addition should be visible before sending the IPI
160          * handler locks the list to pull the entry off it because of
161          * normal cache coherency rules implied by spinlocks.
162          *
163          * If IPIs can go out of order to the cache coherency protocol
164          * in an architecture, sufficient synchronisation should be added
165          * to arch code to make it appear to obey cache coherency WRT
166          * locking and barrier primitives. Generic code isn't really
167          * equipped to do the right thing...
168          */
169         if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
170                 arch_send_call_function_single_ipi(cpu);
171 
172         return 0;
173 }
174 
175 /**
176  * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
177  *
178  * Invoked by arch to handle an IPI for call function single.
179  * Must be called with interrupts disabled.
180  */
181 void generic_smp_call_function_single_interrupt(void)
182 {
183         flush_smp_call_function_queue(true);
184 }
185 
186 /**
187  * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
188  *
189  * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
190  *                    offline CPU. Skip this check if set to 'false'.
191  *
192  * Flush any pending smp-call-function callbacks queued on this CPU. This is
193  * invoked by the generic IPI handler, as well as by a CPU about to go offline,
194  * to ensure that all pending IPI callbacks are run before it goes completely
195  * offline.
196  *
197  * Loop through the call_single_queue and run all the queued callbacks.
198  * Must be called with interrupts disabled.
199  */
200 static void flush_smp_call_function_queue(bool warn_cpu_offline)
201 {
202         struct llist_head *head;
203         struct llist_node *entry;
204         struct call_single_data *csd, *csd_next;
205         static bool warned;
206 
207         WARN_ON(!irqs_disabled());
208 
209         head = this_cpu_ptr(&call_single_queue);
210         entry = llist_del_all(head);
211         entry = llist_reverse_order(entry);
212 
213         /* There shouldn't be any pending callbacks on an offline CPU. */
214         if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
215                      !warned && !llist_empty(head))) {
216                 warned = true;
217                 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
218 
219                 /*
220                  * We don't have to use the _safe() variant here
221                  * because we are not invoking the IPI handlers yet.
222                  */
223                 llist_for_each_entry(csd, entry, llist)
224                         pr_warn("IPI callback %pS sent to offline CPU\n",
225                                 csd->func);
226         }
227 
228         llist_for_each_entry_safe(csd, csd_next, entry, llist) {
229                 smp_call_func_t func = csd->func;
230                 void *info = csd->info;
231 
232                 /* Do we wait until *after* callback? */
233                 if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
234                         func(info);
235                         csd_unlock(csd);
236                 } else {
237                         csd_unlock(csd);
238                         func(info);
239                 }
240         }
241 
242         /*
243          * Handle irq works queued remotely by irq_work_queue_on().
244          * Smp functions above are typically synchronous so they
245          * better run first since some other CPUs may be busy waiting
246          * for them.
247          */
248         irq_work_run();
249 }
250 
251 /*
252  * smp_call_function_single - Run a function on a specific CPU
253  * @func: The function to run. This must be fast and non-blocking.
254  * @info: An arbitrary pointer to pass to the function.
255  * @wait: If true, wait until function has completed on other CPUs.
256  *
257  * Returns 0 on success, else a negative status code.
258  */
259 int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
260                              int wait)
261 {
262         struct call_single_data *csd;
263         struct call_single_data csd_stack = { .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS };
264         int this_cpu;
265         int err;
266 
267         /*
268          * prevent preemption and reschedule on another processor,
269          * as well as CPU removal
270          */
271         this_cpu = get_cpu();
272 
273         /*
274          * Can deadlock when called with interrupts disabled.
275          * We allow cpu's that are not yet online though, as no one else can
276          * send smp call function interrupt to this cpu and as such deadlocks
277          * can't happen.
278          */
279         WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
280                      && !oops_in_progress);
281 
282         csd = &csd_stack;
283         if (!wait) {
284                 csd = this_cpu_ptr(&csd_data);
285                 csd_lock(csd);
286         }
287 
288         err = generic_exec_single(cpu, csd, func, info);
289 
290         if (wait)
291                 csd_lock_wait(csd);
292 
293         put_cpu();
294 
295         return err;
296 }
297 EXPORT_SYMBOL(smp_call_function_single);
298 
299 /**
300  * smp_call_function_single_async(): Run an asynchronous function on a
301  *                               specific CPU.
302  * @cpu: The CPU to run on.
303  * @csd: Pre-allocated and setup data structure
304  *
305  * Like smp_call_function_single(), but the call is asynchonous and
306  * can thus be done from contexts with disabled interrupts.
307  *
308  * The caller passes his own pre-allocated data structure
309  * (ie: embedded in an object) and is responsible for synchronizing it
310  * such that the IPIs performed on the @csd are strictly serialized.
311  *
312  * NOTE: Be careful, there is unfortunately no current debugging facility to
313  * validate the correctness of this serialization.
314  */
315 int smp_call_function_single_async(int cpu, struct call_single_data *csd)
316 {
317         int err = 0;
318 
319         preempt_disable();
320 
321         /* We could deadlock if we have to wait here with interrupts disabled! */
322         if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
323                 csd_lock_wait(csd);
324 
325         csd->flags = CSD_FLAG_LOCK;
326         smp_wmb();
327 
328         err = generic_exec_single(cpu, csd, csd->func, csd->info);
329         preempt_enable();
330 
331         return err;
332 }
333 EXPORT_SYMBOL_GPL(smp_call_function_single_async);
334 
335 /*
336  * smp_call_function_any - Run a function on any of the given cpus
337  * @mask: The mask of cpus it can run on.
338  * @func: The function to run. This must be fast and non-blocking.
339  * @info: An arbitrary pointer to pass to the function.
340  * @wait: If true, wait until function has completed.
341  *
342  * Returns 0 on success, else a negative status code (if no cpus were online).
343  *
344  * Selection preference:
345  *      1) current cpu if in @mask
346  *      2) any cpu of current node if in @mask
347  *      3) any other online cpu in @mask
348  */
349 int smp_call_function_any(const struct cpumask *mask,
350                           smp_call_func_t func, void *info, int wait)
351 {
352         unsigned int cpu;
353         const struct cpumask *nodemask;
354         int ret;
355 
356         /* Try for same CPU (cheapest) */
357         cpu = get_cpu();
358         if (cpumask_test_cpu(cpu, mask))
359                 goto call;
360 
361         /* Try for same node. */
362         nodemask = cpumask_of_node(cpu_to_node(cpu));
363         for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
364              cpu = cpumask_next_and(cpu, nodemask, mask)) {
365                 if (cpu_online(cpu))
366                         goto call;
367         }
368 
369         /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
370         cpu = cpumask_any_and(mask, cpu_online_mask);
371 call:
372         ret = smp_call_function_single(cpu, func, info, wait);
373         put_cpu();
374         return ret;
375 }
376 EXPORT_SYMBOL_GPL(smp_call_function_any);
377 
378 /**
379  * smp_call_function_many(): Run a function on a set of other CPUs.
380  * @mask: The set of cpus to run on (only runs on online subset).
381  * @func: The function to run. This must be fast and non-blocking.
382  * @info: An arbitrary pointer to pass to the function.
383  * @wait: If true, wait (atomically) until function has completed
384  *        on other CPUs.
385  *
386  * If @wait is true, then returns once @func has returned.
387  *
388  * You must not call this function with disabled interrupts or from a
389  * hardware interrupt handler or from a bottom half handler. Preemption
390  * must be disabled when calling this function.
391  */
392 void smp_call_function_many(const struct cpumask *mask,
393                             smp_call_func_t func, void *info, bool wait)
394 {
395         struct call_function_data *cfd;
396         int cpu, next_cpu, this_cpu = smp_processor_id();
397 
398         /*
399          * Can deadlock when called with interrupts disabled.
400          * We allow cpu's that are not yet online though, as no one else can
401          * send smp call function interrupt to this cpu and as such deadlocks
402          * can't happen.
403          */
404         WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
405                      && !oops_in_progress && !early_boot_irqs_disabled);
406 
407         /* Try to fastpath.  So, what's a CPU they want? Ignoring this one. */
408         cpu = cpumask_first_and(mask, cpu_online_mask);
409         if (cpu == this_cpu)
410                 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
411 
412         /* No online cpus?  We're done. */
413         if (cpu >= nr_cpu_ids)
414                 return;
415 
416         /* Do we have another CPU which isn't us? */
417         next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
418         if (next_cpu == this_cpu)
419                 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
420 
421         /* Fastpath: do that cpu by itself. */
422         if (next_cpu >= nr_cpu_ids) {
423                 smp_call_function_single(cpu, func, info, wait);
424                 return;
425         }
426 
427         cfd = this_cpu_ptr(&cfd_data);
428 
429         cpumask_and(cfd->cpumask, mask, cpu_online_mask);
430         cpumask_clear_cpu(this_cpu, cfd->cpumask);
431 
432         /* Some callers race with other cpus changing the passed mask */
433         if (unlikely(!cpumask_weight(cfd->cpumask)))
434                 return;
435 
436         for_each_cpu(cpu, cfd->cpumask) {
437                 struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
438 
439                 csd_lock(csd);
440                 if (wait)
441                         csd->flags |= CSD_FLAG_SYNCHRONOUS;
442                 csd->func = func;
443                 csd->info = info;
444                 llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
445         }
446 
447         /* Send a message to all CPUs in the map */
448         arch_send_call_function_ipi_mask(cfd->cpumask);
449 
450         if (wait) {
451                 for_each_cpu(cpu, cfd->cpumask) {
452                         struct call_single_data *csd;
453 
454                         csd = per_cpu_ptr(cfd->csd, cpu);
455                         csd_lock_wait(csd);
456                 }
457         }
458 }
459 EXPORT_SYMBOL(smp_call_function_many);
460 
461 /**
462  * smp_call_function(): Run a function on all other CPUs.
463  * @func: The function to run. This must be fast and non-blocking.
464  * @info: An arbitrary pointer to pass to the function.
465  * @wait: If true, wait (atomically) until function has completed
466  *        on other CPUs.
467  *
468  * Returns 0.
469  *
470  * If @wait is true, then returns once @func has returned; otherwise
471  * it returns just before the target cpu calls @func.
472  *
473  * You must not call this function with disabled interrupts or from a
474  * hardware interrupt handler or from a bottom half handler.
475  */
476 int smp_call_function(smp_call_func_t func, void *info, int wait)
477 {
478         preempt_disable();
479         smp_call_function_many(cpu_online_mask, func, info, wait);
480         preempt_enable();
481 
482         return 0;
483 }
484 EXPORT_SYMBOL(smp_call_function);
485 
486 /* Setup configured maximum number of CPUs to activate */
487 unsigned int setup_max_cpus = NR_CPUS;
488 EXPORT_SYMBOL(setup_max_cpus);
489 
490 
491 /*
492  * Setup routine for controlling SMP activation
493  *
494  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
495  * activation entirely (the MPS table probe still happens, though).
496  *
497  * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
498  * greater than 0, limits the maximum number of CPUs activated in
499  * SMP mode to <NUM>.
500  */
501 
502 void __weak arch_disable_smp_support(void) { }
503 
504 static int __init nosmp(char *str)
505 {
506         setup_max_cpus = 0;
507         arch_disable_smp_support();
508 
509         return 0;
510 }
511 
512 early_param("nosmp", nosmp);
513 
514 /* this is hard limit */
515 static int __init nrcpus(char *str)
516 {
517         int nr_cpus;
518 
519         get_option(&str, &nr_cpus);
520         if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
521                 nr_cpu_ids = nr_cpus;
522 
523         return 0;
524 }
525 
526 early_param("nr_cpus", nrcpus);
527 
528 static int __init maxcpus(char *str)
529 {
530         get_option(&str, &setup_max_cpus);
531         if (setup_max_cpus == 0)
532                 arch_disable_smp_support();
533 
534         return 0;
535 }
536 
537 early_param("maxcpus", maxcpus);
538 
539 /* Setup number of possible processor ids */
540 int nr_cpu_ids __read_mostly = NR_CPUS;
541 EXPORT_SYMBOL(nr_cpu_ids);
542 
543 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
544 void __init setup_nr_cpu_ids(void)
545 {
546         nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
547 }
548 
549 /* Called by boot processor to activate the rest. */
550 void __init smp_init(void)
551 {
552         int num_nodes, num_cpus;
553         unsigned int cpu;
554 
555         idle_threads_init();
556         cpuhp_threads_init();
557 
558         pr_info("Bringing up secondary CPUs ...\n");
559 
560         /* FIXME: This should be done in userspace --RR */
561         for_each_present_cpu(cpu) {
562                 if (num_online_cpus() >= setup_max_cpus)
563                         break;
564                 if (!cpu_online(cpu))
565                         cpu_up(cpu);
566         }
567 
568         num_nodes = num_online_nodes();
569         num_cpus  = num_online_cpus();
570         pr_info("Brought up %d node%s, %d CPU%s\n",
571                 num_nodes, (num_nodes > 1 ? "s" : ""),
572                 num_cpus,  (num_cpus  > 1 ? "s" : ""));
573 
574         /* Any cleanup work */
575         smp_cpus_done(setup_max_cpus);
576 }
577 
578 /*
579  * Call a function on all processors.  May be used during early boot while
580  * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead
581  * of local_irq_disable/enable().
582  */
583 int on_each_cpu(void (*func) (void *info), void *info, int wait)
584 {
585         unsigned long flags;
586         int ret = 0;
587 
588         preempt_disable();
589         ret = smp_call_function(func, info, wait);
590         local_irq_save(flags);
591         func(info);
592         local_irq_restore(flags);
593         preempt_enable();
594         return ret;
595 }
596 EXPORT_SYMBOL(on_each_cpu);
597 
598 /**
599  * on_each_cpu_mask(): Run a function on processors specified by
600  * cpumask, which may include the local processor.
601  * @mask: The set of cpus to run on (only runs on online subset).
602  * @func: The function to run. This must be fast and non-blocking.
603  * @info: An arbitrary pointer to pass to the function.
604  * @wait: If true, wait (atomically) until function has completed
605  *        on other CPUs.
606  *
607  * If @wait is true, then returns once @func has returned.
608  *
609  * You must not call this function with disabled interrupts or from a
610  * hardware interrupt handler or from a bottom half handler.  The
611  * exception is that it may be used during early boot while
612  * early_boot_irqs_disabled is set.
613  */
614 void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
615                         void *info, bool wait)
616 {
617         int cpu = get_cpu();
618 
619         smp_call_function_many(mask, func, info, wait);
620         if (cpumask_test_cpu(cpu, mask)) {
621                 unsigned long flags;
622                 local_irq_save(flags);
623                 func(info);
624                 local_irq_restore(flags);
625         }
626         put_cpu();
627 }
628 EXPORT_SYMBOL(on_each_cpu_mask);
629 
630 /*
631  * on_each_cpu_cond(): Call a function on each processor for which
632  * the supplied function cond_func returns true, optionally waiting
633  * for all the required CPUs to finish. This may include the local
634  * processor.
635  * @cond_func:  A callback function that is passed a cpu id and
636  *              the the info parameter. The function is called
637  *              with preemption disabled. The function should
638  *              return a blooean value indicating whether to IPI
639  *              the specified CPU.
640  * @func:       The function to run on all applicable CPUs.
641  *              This must be fast and non-blocking.
642  * @info:       An arbitrary pointer to pass to both functions.
643  * @wait:       If true, wait (atomically) until function has
644  *              completed on other CPUs.
645  * @gfp_flags:  GFP flags to use when allocating the cpumask
646  *              used internally by the function.
647  *
648  * The function might sleep if the GFP flags indicates a non
649  * atomic allocation is allowed.
650  *
651  * Preemption is disabled to protect against CPUs going offline but not online.
652  * CPUs going online during the call will not be seen or sent an IPI.
653  *
654  * You must not call this function with disabled interrupts or
655  * from a hardware interrupt handler or from a bottom half handler.
656  */
657 void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
658                         smp_call_func_t func, void *info, bool wait,
659                         gfp_t gfp_flags)
660 {
661         cpumask_var_t cpus;
662         int cpu, ret;
663 
664         might_sleep_if(gfpflags_allow_blocking(gfp_flags));
665 
666         if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
667                 preempt_disable();
668                 for_each_online_cpu(cpu)
669                         if (cond_func(cpu, info))
670                                 cpumask_set_cpu(cpu, cpus);
671                 on_each_cpu_mask(cpus, func, info, wait);
672                 preempt_enable();
673                 free_cpumask_var(cpus);
674         } else {
675                 /*
676                  * No free cpumask, bother. No matter, we'll
677                  * just have to IPI them one by one.
678                  */
679                 preempt_disable();
680                 for_each_online_cpu(cpu)
681                         if (cond_func(cpu, info)) {
682                                 ret = smp_call_function_single(cpu, func,
683                                                                 info, wait);
684                                 WARN_ON_ONCE(ret);
685                         }
686                 preempt_enable();
687         }
688 }
689 EXPORT_SYMBOL(on_each_cpu_cond);
690 
691 static void do_nothing(void *unused)
692 {
693 }
694 
695 /**
696  * kick_all_cpus_sync - Force all cpus out of idle
697  *
698  * Used to synchronize the update of pm_idle function pointer. It's
699  * called after the pointer is updated and returns after the dummy
700  * callback function has been executed on all cpus. The execution of
701  * the function can only happen on the remote cpus after they have
702  * left the idle function which had been called via pm_idle function
703  * pointer. So it's guaranteed that nothing uses the previous pointer
704  * anymore.
705  */
706 void kick_all_cpus_sync(void)
707 {
708         /* Make sure the change is visible before we kick the cpus */
709         smp_mb();
710         smp_call_function(do_nothing, NULL, 1);
711 }
712 EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
713 
714 /**
715  * wake_up_all_idle_cpus - break all cpus out of idle
716  * wake_up_all_idle_cpus try to break all cpus which is in idle state even
717  * including idle polling cpus, for non-idle cpus, we will do nothing
718  * for them.
719  */
720 void wake_up_all_idle_cpus(void)
721 {
722         int cpu;
723 
724         preempt_disable();
725         for_each_online_cpu(cpu) {
726                 if (cpu == smp_processor_id())
727                         continue;
728 
729                 wake_up_if_idle(cpu);
730         }
731         preempt_enable();
732 }
733 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
734 
735 /**
736  * smp_call_on_cpu - Call a function on a specific cpu
737  *
738  * Used to call a function on a specific cpu and wait for it to return.
739  * Optionally make sure the call is done on a specified physical cpu via vcpu
740  * pinning in order to support virtualized environments.
741  */
742 struct smp_call_on_cpu_struct {
743         struct work_struct      work;
744         struct completion       done;
745         int                     (*func)(void *);
746         void                    *data;
747         int                     ret;
748         int                     cpu;
749 };
750 
751 static void smp_call_on_cpu_callback(struct work_struct *work)
752 {
753         struct smp_call_on_cpu_struct *sscs;
754 
755         sscs = container_of(work, struct smp_call_on_cpu_struct, work);
756         if (sscs->cpu >= 0)
757                 hypervisor_pin_vcpu(sscs->cpu);
758         sscs->ret = sscs->func(sscs->data);
759         if (sscs->cpu >= 0)
760                 hypervisor_pin_vcpu(-1);
761 
762         complete(&sscs->done);
763 }
764 
765 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
766 {
767         struct smp_call_on_cpu_struct sscs = {
768                 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
769                 .func = func,
770                 .data = par,
771                 .cpu  = phys ? cpu : -1,
772         };
773 
774         INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
775 
776         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
777                 return -ENXIO;
778 
779         queue_work_on(cpu, system_wq, &sscs.work);
780         wait_for_completion(&sscs.done);
781 
782         return sscs.ret;
783 }
784 EXPORT_SYMBOL_GPL(smp_call_on_cpu);
785 

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