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TOMOYO Linux Cross Reference
Linux/kernel/smp.c

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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
 19 enum {
 20         CSD_FLAG_LOCK           = 0x01,
 21 };
 22 
 23 struct call_function_data {
 24         struct call_single_data __percpu *csd;
 25         cpumask_var_t           cpumask;
 26         cpumask_var_t           cpumask_ipi;
 27 };
 28 
 29 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
 30 
 31 struct call_single_queue {
 32         struct list_head        list;
 33         raw_spinlock_t          lock;
 34 };
 35 
 36 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
 37 
 38 static int
 39 hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
 40 {
 41         long cpu = (long)hcpu;
 42         struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
 43 
 44         switch (action) {
 45         case CPU_UP_PREPARE:
 46         case CPU_UP_PREPARE_FROZEN:
 47                 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
 48                                 cpu_to_node(cpu)))
 49                         return notifier_from_errno(-ENOMEM);
 50                 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
 51                                 cpu_to_node(cpu)))
 52                         return notifier_from_errno(-ENOMEM);
 53                 cfd->csd = alloc_percpu(struct call_single_data);
 54                 if (!cfd->csd) {
 55                         free_cpumask_var(cfd->cpumask);
 56                         return notifier_from_errno(-ENOMEM);
 57                 }
 58                 break;
 59 
 60 #ifdef CONFIG_HOTPLUG_CPU
 61         case CPU_UP_CANCELED:
 62         case CPU_UP_CANCELED_FROZEN:
 63 
 64         case CPU_DEAD:
 65         case CPU_DEAD_FROZEN:
 66                 free_cpumask_var(cfd->cpumask);
 67                 free_cpumask_var(cfd->cpumask_ipi);
 68                 free_percpu(cfd->csd);
 69                 break;
 70 #endif
 71         };
 72 
 73         return NOTIFY_OK;
 74 }
 75 
 76 static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
 77         .notifier_call          = hotplug_cfd,
 78 };
 79 
 80 void __init call_function_init(void)
 81 {
 82         void *cpu = (void *)(long)smp_processor_id();
 83         int i;
 84 
 85         for_each_possible_cpu(i) {
 86                 struct call_single_queue *q = &per_cpu(call_single_queue, i);
 87 
 88                 raw_spin_lock_init(&q->lock);
 89                 INIT_LIST_HEAD(&q->list);
 90         }
 91 
 92         hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
 93         register_cpu_notifier(&hotplug_cfd_notifier);
 94 }
 95 
 96 /*
 97  * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
 98  *
 99  * For non-synchronous ipi calls the csd can still be in use by the
100  * previous function call. For multi-cpu calls its even more interesting
101  * as we'll have to ensure no other cpu is observing our csd.
102  */
103 static void csd_lock_wait(struct call_single_data *data)
104 {
105         while (data->flags & CSD_FLAG_LOCK)
106                 cpu_relax();
107 }
108 
109 static void csd_lock(struct call_single_data *data)
110 {
111         csd_lock_wait(data);
112         data->flags = CSD_FLAG_LOCK;
113 
114         /*
115          * prevent CPU from reordering the above assignment
116          * to ->flags with any subsequent assignments to other
117          * fields of the specified call_single_data structure:
118          */
119         smp_mb();
120 }
121 
122 static void csd_unlock(struct call_single_data *data)
123 {
124         WARN_ON(!(data->flags & CSD_FLAG_LOCK));
125 
126         /*
127          * ensure we're all done before releasing data:
128          */
129         smp_mb();
130 
131         data->flags &= ~CSD_FLAG_LOCK;
132 }
133 
134 /*
135  * Insert a previously allocated call_single_data element
136  * for execution on the given CPU. data must already have
137  * ->func, ->info, and ->flags set.
138  */
139 static
140 void generic_exec_single(int cpu, struct call_single_data *data, int wait)
141 {
142         struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
143         unsigned long flags;
144         int ipi;
145 
146         raw_spin_lock_irqsave(&dst->lock, flags);
147         ipi = list_empty(&dst->list);
148         list_add_tail(&data->list, &dst->list);
149         raw_spin_unlock_irqrestore(&dst->lock, flags);
150 
151         /*
152          * The list addition should be visible before sending the IPI
153          * handler locks the list to pull the entry off it because of
154          * normal cache coherency rules implied by spinlocks.
155          *
156          * If IPIs can go out of order to the cache coherency protocol
157          * in an architecture, sufficient synchronisation should be added
158          * to arch code to make it appear to obey cache coherency WRT
159          * locking and barrier primitives. Generic code isn't really
160          * equipped to do the right thing...
161          */
162         if (ipi)
163                 arch_send_call_function_single_ipi(cpu);
164 
165         if (wait)
166                 csd_lock_wait(data);
167 }
168 
169 /*
170  * Invoked by arch to handle an IPI for call function single. Must be
171  * called from the arch with interrupts disabled.
172  */
173 void generic_smp_call_function_single_interrupt(void)
174 {
175         struct call_single_queue *q = &__get_cpu_var(call_single_queue);
176         unsigned int data_flags;
177         LIST_HEAD(list);
178 
179         /*
180          * Shouldn't receive this interrupt on a cpu that is not yet online.
181          */
182         WARN_ON_ONCE(!cpu_online(smp_processor_id()));
183 
184         raw_spin_lock(&q->lock);
185         list_replace_init(&q->list, &list);
186         raw_spin_unlock(&q->lock);
187 
188         while (!list_empty(&list)) {
189                 struct call_single_data *data;
190 
191                 data = list_entry(list.next, struct call_single_data, list);
192                 list_del(&data->list);
193 
194                 /*
195                  * 'data' can be invalid after this call if flags == 0
196                  * (when called through generic_exec_single()),
197                  * so save them away before making the call:
198                  */
199                 data_flags = data->flags;
200 
201                 data->func(data->info);
202 
203                 /*
204                  * Unlocked CSDs are valid through generic_exec_single():
205                  */
206                 if (data_flags & CSD_FLAG_LOCK)
207                         csd_unlock(data);
208         }
209 }
210 
211 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
212 
213 /*
214  * smp_call_function_single - Run a function on a specific CPU
215  * @func: The function to run. This must be fast and non-blocking.
216  * @info: An arbitrary pointer to pass to the function.
217  * @wait: If true, wait until function has completed on other CPUs.
218  *
219  * Returns 0 on success, else a negative status code.
220  */
221 int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
222                              int wait)
223 {
224         struct call_single_data d = {
225                 .flags = 0,
226         };
227         unsigned long flags;
228         int this_cpu;
229         int err = 0;
230 
231         /*
232          * prevent preemption and reschedule on another processor,
233          * as well as CPU removal
234          */
235         this_cpu = get_cpu();
236 
237         /*
238          * Can deadlock when called with interrupts disabled.
239          * We allow cpu's that are not yet online though, as no one else can
240          * send smp call function interrupt to this cpu and as such deadlocks
241          * can't happen.
242          */
243         WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
244                      && !oops_in_progress);
245 
246         if (cpu == this_cpu) {
247                 local_irq_save(flags);
248                 func(info);
249                 local_irq_restore(flags);
250         } else {
251                 if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
252                         struct call_single_data *data = &d;
253 
254                         if (!wait)
255                                 data = &__get_cpu_var(csd_data);
256 
257                         csd_lock(data);
258 
259                         data->func = func;
260                         data->info = info;
261                         generic_exec_single(cpu, data, wait);
262                 } else {
263                         err = -ENXIO;   /* CPU not online */
264                 }
265         }
266 
267         put_cpu();
268 
269         return err;
270 }
271 EXPORT_SYMBOL(smp_call_function_single);
272 
273 /*
274  * smp_call_function_any - Run a function on any of the given cpus
275  * @mask: The mask of cpus it can run on.
276  * @func: The function to run. This must be fast and non-blocking.
277  * @info: An arbitrary pointer to pass to the function.
278  * @wait: If true, wait until function has completed.
279  *
280  * Returns 0 on success, else a negative status code (if no cpus were online).
281  * Note that @wait will be implicitly turned on in case of allocation failures,
282  * since we fall back to on-stack allocation.
283  *
284  * Selection preference:
285  *      1) current cpu if in @mask
286  *      2) any cpu of current node if in @mask
287  *      3) any other online cpu in @mask
288  */
289 int smp_call_function_any(const struct cpumask *mask,
290                           smp_call_func_t func, void *info, int wait)
291 {
292         unsigned int cpu;
293         const struct cpumask *nodemask;
294         int ret;
295 
296         /* Try for same CPU (cheapest) */
297         cpu = get_cpu();
298         if (cpumask_test_cpu(cpu, mask))
299                 goto call;
300 
301         /* Try for same node. */
302         nodemask = cpumask_of_node(cpu_to_node(cpu));
303         for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
304              cpu = cpumask_next_and(cpu, nodemask, mask)) {
305                 if (cpu_online(cpu))
306                         goto call;
307         }
308 
309         /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
310         cpu = cpumask_any_and(mask, cpu_online_mask);
311 call:
312         ret = smp_call_function_single(cpu, func, info, wait);
313         put_cpu();
314         return ret;
315 }
316 EXPORT_SYMBOL_GPL(smp_call_function_any);
317 
318 /**
319  * __smp_call_function_single(): Run a function on a specific CPU
320  * @cpu: The CPU to run on.
321  * @data: Pre-allocated and setup data structure
322  * @wait: If true, wait until function has completed on specified CPU.
323  *
324  * Like smp_call_function_single(), but allow caller to pass in a
325  * pre-allocated data structure. Useful for embedding @data inside
326  * other structures, for instance.
327  */
328 void __smp_call_function_single(int cpu, struct call_single_data *data,
329                                 int wait)
330 {
331         unsigned int this_cpu;
332         unsigned long flags;
333 
334         this_cpu = get_cpu();
335         /*
336          * Can deadlock when called with interrupts disabled.
337          * We allow cpu's that are not yet online though, as no one else can
338          * send smp call function interrupt to this cpu and as such deadlocks
339          * can't happen.
340          */
341         WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
342                      && !oops_in_progress);
343 
344         if (cpu == this_cpu) {
345                 local_irq_save(flags);
346                 data->func(data->info);
347                 local_irq_restore(flags);
348         } else {
349                 csd_lock(data);
350                 generic_exec_single(cpu, data, wait);
351         }
352         put_cpu();
353 }
354 
355 /**
356  * smp_call_function_many(): Run a function on a set of other CPUs.
357  * @mask: The set of cpus to run on (only runs on online subset).
358  * @func: The function to run. This must be fast and non-blocking.
359  * @info: An arbitrary pointer to pass to the function.
360  * @wait: If true, wait (atomically) until function has completed
361  *        on other CPUs.
362  *
363  * If @wait is true, then returns once @func has returned.
364  *
365  * You must not call this function with disabled interrupts or from a
366  * hardware interrupt handler or from a bottom half handler. Preemption
367  * must be disabled when calling this function.
368  */
369 void smp_call_function_many(const struct cpumask *mask,
370                             smp_call_func_t func, void *info, bool wait)
371 {
372         struct call_function_data *data;
373         int cpu, next_cpu, this_cpu = smp_processor_id();
374 
375         /*
376          * Can deadlock when called with interrupts disabled.
377          * We allow cpu's that are not yet online though, as no one else can
378          * send smp call function interrupt to this cpu and as such deadlocks
379          * can't happen.
380          */
381         WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
382                      && !oops_in_progress && !early_boot_irqs_disabled);
383 
384         /* Try to fastpath.  So, what's a CPU they want? Ignoring this one. */
385         cpu = cpumask_first_and(mask, cpu_online_mask);
386         if (cpu == this_cpu)
387                 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
388 
389         /* No online cpus?  We're done. */
390         if (cpu >= nr_cpu_ids)
391                 return;
392 
393         /* Do we have another CPU which isn't us? */
394         next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
395         if (next_cpu == this_cpu)
396                 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
397 
398         /* Fastpath: do that cpu by itself. */
399         if (next_cpu >= nr_cpu_ids) {
400                 smp_call_function_single(cpu, func, info, wait);
401                 return;
402         }
403 
404         data = &__get_cpu_var(cfd_data);
405 
406         cpumask_and(data->cpumask, mask, cpu_online_mask);
407         cpumask_clear_cpu(this_cpu, data->cpumask);
408 
409         /* Some callers race with other cpus changing the passed mask */
410         if (unlikely(!cpumask_weight(data->cpumask)))
411                 return;
412 
413         /*
414          * After we put an entry into the list, data->cpumask
415          * may be cleared again when another CPU sends another IPI for
416          * a SMP function call, so data->cpumask will be zero.
417          */
418         cpumask_copy(data->cpumask_ipi, data->cpumask);
419 
420         for_each_cpu(cpu, data->cpumask) {
421                 struct call_single_data *csd = per_cpu_ptr(data->csd, cpu);
422                 struct call_single_queue *dst =
423                                         &per_cpu(call_single_queue, cpu);
424                 unsigned long flags;
425 
426                 csd_lock(csd);
427                 csd->func = func;
428                 csd->info = info;
429 
430                 raw_spin_lock_irqsave(&dst->lock, flags);
431                 list_add_tail(&csd->list, &dst->list);
432                 raw_spin_unlock_irqrestore(&dst->lock, flags);
433         }
434 
435         /* Send a message to all CPUs in the map */
436         arch_send_call_function_ipi_mask(data->cpumask_ipi);
437 
438         if (wait) {
439                 for_each_cpu(cpu, data->cpumask) {
440                         struct call_single_data *csd =
441                                         per_cpu_ptr(data->csd, cpu);
442                         csd_lock_wait(csd);
443                 }
444         }
445 }
446 EXPORT_SYMBOL(smp_call_function_many);
447 
448 /**
449  * smp_call_function(): Run a function on all other CPUs.
450  * @func: The function to run. This must be fast and non-blocking.
451  * @info: An arbitrary pointer to pass to the function.
452  * @wait: If true, wait (atomically) until function has completed
453  *        on other CPUs.
454  *
455  * Returns 0.
456  *
457  * If @wait is true, then returns once @func has returned; otherwise
458  * it returns just before the target cpu calls @func.
459  *
460  * You must not call this function with disabled interrupts or from a
461  * hardware interrupt handler or from a bottom half handler.
462  */
463 int smp_call_function(smp_call_func_t func, void *info, int wait)
464 {
465         preempt_disable();
466         smp_call_function_many(cpu_online_mask, func, info, wait);
467         preempt_enable();
468 
469         return 0;
470 }
471 EXPORT_SYMBOL(smp_call_function);
472 #endif /* USE_GENERIC_SMP_HELPERS */
473 
474 /* Setup configured maximum number of CPUs to activate */
475 unsigned int setup_max_cpus = NR_CPUS;
476 EXPORT_SYMBOL(setup_max_cpus);
477 
478 
479 /*
480  * Setup routine for controlling SMP activation
481  *
482  * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
483  * activation entirely (the MPS table probe still happens, though).
484  *
485  * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
486  * greater than 0, limits the maximum number of CPUs activated in
487  * SMP mode to <NUM>.
488  */
489 
490 void __weak arch_disable_smp_support(void) { }
491 
492 static int __init nosmp(char *str)
493 {
494         setup_max_cpus = 0;
495         arch_disable_smp_support();
496 
497         return 0;
498 }
499 
500 early_param("nosmp", nosmp);
501 
502 /* this is hard limit */
503 static int __init nrcpus(char *str)
504 {
505         int nr_cpus;
506 
507         get_option(&str, &nr_cpus);
508         if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
509                 nr_cpu_ids = nr_cpus;
510 
511         return 0;
512 }
513 
514 early_param("nr_cpus", nrcpus);
515 
516 static int __init maxcpus(char *str)
517 {
518         get_option(&str, &setup_max_cpus);
519         if (setup_max_cpus == 0)
520                 arch_disable_smp_support();
521 
522         return 0;
523 }
524 
525 early_param("maxcpus", maxcpus);
526 
527 /* Setup number of possible processor ids */
528 int nr_cpu_ids __read_mostly = NR_CPUS;
529 EXPORT_SYMBOL(nr_cpu_ids);
530 
531 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
532 void __init setup_nr_cpu_ids(void)
533 {
534         nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
535 }
536 
537 /* Called by boot processor to activate the rest. */
538 void __init smp_init(void)
539 {
540         unsigned int cpu;
541 
542         idle_threads_init();
543 
544         /* FIXME: This should be done in userspace --RR */
545         for_each_present_cpu(cpu) {
546                 if (num_online_cpus() >= setup_max_cpus)
547                         break;
548                 if (!cpu_online(cpu))
549                         cpu_up(cpu);
550         }
551 
552         /* Any cleanup work */
553         printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
554         smp_cpus_done(setup_max_cpus);
555 }
556 
557 /*
558  * Call a function on all processors.  May be used during early boot while
559  * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead
560  * of local_irq_disable/enable().
561  */
562 int on_each_cpu(void (*func) (void *info), void *info, int wait)
563 {
564         unsigned long flags;
565         int ret = 0;
566 
567         preempt_disable();
568         ret = smp_call_function(func, info, wait);
569         local_irq_save(flags);
570         func(info);
571         local_irq_restore(flags);
572         preempt_enable();
573         return ret;
574 }
575 EXPORT_SYMBOL(on_each_cpu);
576 
577 /**
578  * on_each_cpu_mask(): Run a function on processors specified by
579  * cpumask, which may include the local processor.
580  * @mask: The set of cpus to run on (only runs on online subset).
581  * @func: The function to run. This must be fast and non-blocking.
582  * @info: An arbitrary pointer to pass to the function.
583  * @wait: If true, wait (atomically) until function has completed
584  *        on other CPUs.
585  *
586  * If @wait is true, then returns once @func has returned.
587  *
588  * You must not call this function with disabled interrupts or
589  * from a hardware interrupt handler or from a bottom half handler.
590  */
591 void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
592                         void *info, bool wait)
593 {
594         int cpu = get_cpu();
595 
596         smp_call_function_many(mask, func, info, wait);
597         if (cpumask_test_cpu(cpu, mask)) {
598                 local_irq_disable();
599                 func(info);
600                 local_irq_enable();
601         }
602         put_cpu();
603 }
604 EXPORT_SYMBOL(on_each_cpu_mask);
605 
606 /*
607  * on_each_cpu_cond(): Call a function on each processor for which
608  * the supplied function cond_func returns true, optionally waiting
609  * for all the required CPUs to finish. This may include the local
610  * processor.
611  * @cond_func:  A callback function that is passed a cpu id and
612  *              the the info parameter. The function is called
613  *              with preemption disabled. The function should
614  *              return a blooean value indicating whether to IPI
615  *              the specified CPU.
616  * @func:       The function to run on all applicable CPUs.
617  *              This must be fast and non-blocking.
618  * @info:       An arbitrary pointer to pass to both functions.
619  * @wait:       If true, wait (atomically) until function has
620  *              completed on other CPUs.
621  * @gfp_flags:  GFP flags to use when allocating the cpumask
622  *              used internally by the function.
623  *
624  * The function might sleep if the GFP flags indicates a non
625  * atomic allocation is allowed.
626  *
627  * Preemption is disabled to protect against CPUs going offline but not online.
628  * CPUs going online during the call will not be seen or sent an IPI.
629  *
630  * You must not call this function with disabled interrupts or
631  * from a hardware interrupt handler or from a bottom half handler.
632  */
633 void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
634                         smp_call_func_t func, void *info, bool wait,
635                         gfp_t gfp_flags)
636 {
637         cpumask_var_t cpus;
638         int cpu, ret;
639 
640         might_sleep_if(gfp_flags & __GFP_WAIT);
641 
642         if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
643                 preempt_disable();
644                 for_each_online_cpu(cpu)
645                         if (cond_func(cpu, info))
646                                 cpumask_set_cpu(cpu, cpus);
647                 on_each_cpu_mask(cpus, func, info, wait);
648                 preempt_enable();
649                 free_cpumask_var(cpus);
650         } else {
651                 /*
652                  * No free cpumask, bother. No matter, we'll
653                  * just have to IPI them one by one.
654                  */
655                 preempt_disable();
656                 for_each_online_cpu(cpu)
657                         if (cond_func(cpu, info)) {
658                                 ret = smp_call_function_single(cpu, func,
659                                                                 info, wait);
660                                 WARN_ON_ONCE(!ret);
661                         }
662                 preempt_enable();
663         }
664 }
665 EXPORT_SYMBOL(on_each_cpu_cond);
666 
667 static void do_nothing(void *unused)
668 {
669 }
670 
671 /**
672  * kick_all_cpus_sync - Force all cpus out of idle
673  *
674  * Used to synchronize the update of pm_idle function pointer. It's
675  * called after the pointer is updated and returns after the dummy
676  * callback function has been executed on all cpus. The execution of
677  * the function can only happen on the remote cpus after they have
678  * left the idle function which had been called via pm_idle function
679  * pointer. So it's guaranteed that nothing uses the previous pointer
680  * anymore.
681  */
682 void kick_all_cpus_sync(void)
683 {
684         /* Make sure the change is visible before we kick the cpus */
685         smp_mb();
686         smp_call_function(do_nothing, NULL, 1);
687 }
688 EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
689 

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