projects/linux·blob v3.13 · refs

688 lines · 18.1 KiB

1/*
2 * Generic helpers for smp ipi calls
3 *
4 * (C) Jens Axboe <[email protected]> 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
18enum {
19 CSD_FLAG_LOCK = 0x01,
20 CSD_FLAG_WAIT = 0x02,
21};
22
23struct call_function_data {
24 struct call_single_data __percpu *csd;
25 cpumask_var_t cpumask;
26 cpumask_var_t cpumask_ipi;
27};
28
29static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
30
31struct call_single_queue {
32 struct list_head list;
33 raw_spinlock_t lock;
34};
35
36static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
37
38static int
39hotplug_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 free_cpumask_var(cfd->cpumask);
53 return notifier_from_errno(-ENOMEM);
54 }
55 cfd->csd = alloc_percpu(struct call_single_data);
56 if (!cfd->csd) {
57 free_cpumask_var(cfd->cpumask_ipi);
58 free_cpumask_var(cfd->cpumask);
59 return notifier_from_errno(-ENOMEM);
60 }
61 break;
62
63#ifdef CONFIG_HOTPLUG_CPU
64 case CPU_UP_CANCELED:
65 case CPU_UP_CANCELED_FROZEN:
66
67 case CPU_DEAD:
68 case CPU_DEAD_FROZEN:
69 free_cpumask_var(cfd->cpumask);
70 free_cpumask_var(cfd->cpumask_ipi);
71 free_percpu(cfd->csd);
72 break;
73#endif
74 };
75
76 return NOTIFY_OK;
77}
78
79static struct notifier_block hotplug_cfd_notifier = {
80 .notifier_call = hotplug_cfd,
81};
82
83void __init call_function_init(void)
84{
85 void *cpu = (void *)(long)smp_processor_id();
86 int i;
87
88 for_each_possible_cpu(i) {
89 struct call_single_queue *q = &per_cpu(call_single_queue, i);
90
91 raw_spin_lock_init(&q->lock);
92 INIT_LIST_HEAD(&q->list);
93 }
94
95 hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
96 register_cpu_notifier(&hotplug_cfd_notifier);
97}
98
99/*
100 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
101 *
102 * For non-synchronous ipi calls the csd can still be in use by the
103 * previous function call. For multi-cpu calls its even more interesting
104 * as we'll have to ensure no other cpu is observing our csd.
105 */
106static void csd_lock_wait(struct call_single_data *csd)
107{
108 while (csd->flags & CSD_FLAG_LOCK)
109 cpu_relax();
110}
111
112static void csd_lock(struct call_single_data *csd)
113{
114 csd_lock_wait(csd);
115 csd->flags |= CSD_FLAG_LOCK;
116
117 /*
118 * prevent CPU from reordering the above assignment
119 * to ->flags with any subsequent assignments to other
120 * fields of the specified call_single_data structure:
121 */
122 smp_mb();
123}
124
125static void csd_unlock(struct call_single_data *csd)
126{
127 WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
128
129 /*
130 * ensure we're all done before releasing data:
131 */
132 smp_mb();
133
134 csd->flags &= ~CSD_FLAG_LOCK;
135}
136
137/*
138 * Insert a previously allocated call_single_data element
139 * for execution on the given CPU. data must already have
140 * ->func, ->info, and ->flags set.
141 */
142static void generic_exec_single(int cpu, struct call_single_data *csd, int wait)
143{
144 struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
145 unsigned long flags;
146 int ipi;
147
148 if (wait)
149 csd->flags |= CSD_FLAG_WAIT;
150
151 raw_spin_lock_irqsave(&dst->lock, flags);
152 ipi = list_empty(&dst->list);
153 list_add_tail(&csd->list, &dst->list);
154 raw_spin_unlock_irqrestore(&dst->lock, flags);
155
156 /*
157 * The list addition should be visible before sending the IPI
158 * handler locks the list to pull the entry off it because of
159 * normal cache coherency rules implied by spinlocks.
160 *
161 * If IPIs can go out of order to the cache coherency protocol
162 * in an architecture, sufficient synchronisation should be added
163 * to arch code to make it appear to obey cache coherency WRT
164 * locking and barrier primitives. Generic code isn't really
165 * equipped to do the right thing...
166 */
167 if (ipi)
168 arch_send_call_function_single_ipi(cpu);
169
170 if (wait)
171 csd_lock_wait(csd);
172}
173
174/*
175 * Invoked by arch to handle an IPI for call function single. Must be
176 * called from the arch with interrupts disabled.
177 */
178void generic_smp_call_function_single_interrupt(void)
179{
180 struct call_single_queue *q = &__get_cpu_var(call_single_queue);
181 LIST_HEAD(list);
182
183 /*
184 * Shouldn't receive this interrupt on a cpu that is not yet online.
185 */
186 WARN_ON_ONCE(!cpu_online(smp_processor_id()));
187
188 raw_spin_lock(&q->lock);
189 list_replace_init(&q->list, &list);
190 raw_spin_unlock(&q->lock);
191
192 while (!list_empty(&list)) {
193 struct call_single_data *csd;
194
195 csd = list_entry(list.next, struct call_single_data, list);
196 list_del(&csd->list);
197
198 csd->func(csd->info);
199
200 csd_unlock(csd);
201 }
202}
203
204static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
205
206/*
207 * smp_call_function_single - Run a function on a specific CPU
208 * @func: The function to run. This must be fast and non-blocking.
209 * @info: An arbitrary pointer to pass to the function.
210 * @wait: If true, wait until function has completed on other CPUs.
211 *
212 * Returns 0 on success, else a negative status code.
213 */
214int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
215 int wait)
216{
217 struct call_single_data d = {
218 .flags = 0,
219 };
220 unsigned long flags;
221 int this_cpu;
222 int err = 0;
223
224 /*
225 * prevent preemption and reschedule on another processor,
226 * as well as CPU removal
227 */
228 this_cpu = get_cpu();
229
230 /*
231 * Can deadlock when called with interrupts disabled.
232 * We allow cpu's that are not yet online though, as no one else can
233 * send smp call function interrupt to this cpu and as such deadlocks
234 * can't happen.
235 */
236 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
237 && !oops_in_progress);
238
239 if (cpu == this_cpu) {
240 local_irq_save(flags);
241 func(info);
242 local_irq_restore(flags);
243 } else {
244 if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
245 struct call_single_data *csd = &d;
246
247 if (!wait)
248 csd = &__get_cpu_var(csd_data);
249
250 csd_lock(csd);
251
252 csd->func = func;
253 csd->info = info;
254 generic_exec_single(cpu, csd, wait);
255 } else {
256 err = -ENXIO; /* CPU not online */
257 }
258 }
259
260 put_cpu();
261
262 return err;
263}
264EXPORT_SYMBOL(smp_call_function_single);
265
266/*
267 * smp_call_function_any - Run a function on any of the given cpus
268 * @mask: The mask of cpus it can run on.
269 * @func: The function to run. This must be fast and non-blocking.
270 * @info: An arbitrary pointer to pass to the function.
271 * @wait: If true, wait until function has completed.
272 *
273 * Returns 0 on success, else a negative status code (if no cpus were online).
274 *
275 * Selection preference:
276 * 1) current cpu if in @mask
277 * 2) any cpu of current node if in @mask
278 * 3) any other online cpu in @mask
279 */
280int smp_call_function_any(const struct cpumask *mask,
281 smp_call_func_t func, void *info, int wait)
282{
283 unsigned int cpu;
284 const struct cpumask *nodemask;
285 int ret;
286
287 /* Try for same CPU (cheapest) */
288 cpu = get_cpu();
289 if (cpumask_test_cpu(cpu, mask))
290 goto call;
291
292 /* Try for same node. */
293 nodemask = cpumask_of_node(cpu_to_node(cpu));
294 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
295 cpu = cpumask_next_and(cpu, nodemask, mask)) {
296 if (cpu_online(cpu))
297 goto call;
298 }
299
300 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
301 cpu = cpumask_any_and(mask, cpu_online_mask);
302call:
303 ret = smp_call_function_single(cpu, func, info, wait);
304 put_cpu();
305 return ret;
306}
307EXPORT_SYMBOL_GPL(smp_call_function_any);
308
309/**
310 * __smp_call_function_single(): Run a function on a specific CPU
311 * @cpu: The CPU to run on.
312 * @data: Pre-allocated and setup data structure
313 * @wait: If true, wait until function has completed on specified CPU.
314 *
315 * Like smp_call_function_single(), but allow caller to pass in a
316 * pre-allocated data structure. Useful for embedding @data inside
317 * other structures, for instance.
318 */
319void __smp_call_function_single(int cpu, struct call_single_data *csd,
320 int wait)
321{
322 unsigned int this_cpu;
323 unsigned long flags;
324
325 this_cpu = get_cpu();
326 /*
327 * Can deadlock when called with interrupts disabled.
328 * We allow cpu's that are not yet online though, as no one else can
329 * send smp call function interrupt to this cpu and as such deadlocks
330 * can't happen.
331 */
332 WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
333 && !oops_in_progress);
334
335 if (cpu == this_cpu) {
336 local_irq_save(flags);
337 csd->func(csd->info);
338 local_irq_restore(flags);
339 } else {
340 csd_lock(csd);
341 generic_exec_single(cpu, csd, wait);
342 }
343 put_cpu();
344}
345EXPORT_SYMBOL_GPL(__smp_call_function_single);
346
347/**
348 * smp_call_function_many(): Run a function on a set of other CPUs.
349 * @mask: The set of cpus to run on (only runs on online subset).
350 * @func: The function to run. This must be fast and non-blocking.
351 * @info: An arbitrary pointer to pass to the function.
352 * @wait: If true, wait (atomically) until function has completed
353 * on other CPUs.
354 *
355 * If @wait is true, then returns once @func has returned.
356 *
357 * You must not call this function with disabled interrupts or from a
358 * hardware interrupt handler or from a bottom half handler. Preemption
359 * must be disabled when calling this function.
360 */
361void smp_call_function_many(const struct cpumask *mask,
362 smp_call_func_t func, void *info, bool wait)
363{
364 struct call_function_data *cfd;
365 int cpu, next_cpu, this_cpu = smp_processor_id();
366
367 /*
368 * Can deadlock when called with interrupts disabled.
369 * We allow cpu's that are not yet online though, as no one else can
370 * send smp call function interrupt to this cpu and as such deadlocks
371 * can't happen.
372 */
373 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
374 && !oops_in_progress && !early_boot_irqs_disabled);
375
376 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
377 cpu = cpumask_first_and(mask, cpu_online_mask);
378 if (cpu == this_cpu)
379 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
380
381 /* No online cpus? We're done. */
382 if (cpu >= nr_cpu_ids)
383 return;
384
385 /* Do we have another CPU which isn't us? */
386 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
387 if (next_cpu == this_cpu)
388 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
389
390 /* Fastpath: do that cpu by itself. */
391 if (next_cpu >= nr_cpu_ids) {
392 smp_call_function_single(cpu, func, info, wait);
393 return;
394 }
395
396 cfd = &__get_cpu_var(cfd_data);
397
398 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
399 cpumask_clear_cpu(this_cpu, cfd->cpumask);
400
401 /* Some callers race with other cpus changing the passed mask */
402 if (unlikely(!cpumask_weight(cfd->cpumask)))
403 return;
404
405 /*
406 * After we put an entry into the list, cfd->cpumask may be cleared
407 * again when another CPU sends another IPI for a SMP function call, so
408 * cfd->cpumask will be zero.
409 */
410 cpumask_copy(cfd->cpumask_ipi, cfd->cpumask);
411
412 for_each_cpu(cpu, cfd->cpumask) {
413 struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
414 struct call_single_queue *dst =
415 &per_cpu(call_single_queue, cpu);
416 unsigned long flags;
417
418 csd_lock(csd);
419 csd->func = func;
420 csd->info = info;
421
422 raw_spin_lock_irqsave(&dst->lock, flags);
423 list_add_tail(&csd->list, &dst->list);
424 raw_spin_unlock_irqrestore(&dst->lock, flags);
425 }
426
427 /* Send a message to all CPUs in the map */
428 arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
429
430 if (wait) {
431 for_each_cpu(cpu, cfd->cpumask) {
432 struct call_single_data *csd;
433
434 csd = per_cpu_ptr(cfd->csd, cpu);
435 csd_lock_wait(csd);
436 }
437 }
438}
439EXPORT_SYMBOL(smp_call_function_many);
440
441/**
442 * smp_call_function(): Run a function on all other CPUs.
443 * @func: The function to run. This must be fast and non-blocking.
444 * @info: An arbitrary pointer to pass to the function.
445 * @wait: If true, wait (atomically) until function has completed
446 * on other CPUs.
447 *
448 * Returns 0.
449 *
450 * If @wait is true, then returns once @func has returned; otherwise
451 * it returns just before the target cpu calls @func.
452 *
453 * You must not call this function with disabled interrupts or from a
454 * hardware interrupt handler or from a bottom half handler.
455 */
456int smp_call_function(smp_call_func_t func, void *info, int wait)
457{
458 preempt_disable();
459 smp_call_function_many(cpu_online_mask, func, info, wait);
460 preempt_enable();
461
462 return 0;
463}
464EXPORT_SYMBOL(smp_call_function);
465
466/* Setup configured maximum number of CPUs to activate */
467unsigned int setup_max_cpus = NR_CPUS;
468EXPORT_SYMBOL(setup_max_cpus);
469
470
471/*
472 * Setup routine for controlling SMP activation
473 *
474 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
475 * activation entirely (the MPS table probe still happens, though).
476 *
477 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
478 * greater than 0, limits the maximum number of CPUs activated in
479 * SMP mode to <NUM>.
480 */
481
482void __weak arch_disable_smp_support(void) { }
483
484static int __init nosmp(char *str)
485{
486 setup_max_cpus = 0;
487 arch_disable_smp_support();
488
489 return 0;
490}
491
492early_param("nosmp", nosmp);
493
494/* this is hard limit */
495static int __init nrcpus(char *str)
496{
497 int nr_cpus;
498
499 get_option(&str, &nr_cpus);
500 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
501 nr_cpu_ids = nr_cpus;
502
503 return 0;
504}
505
506early_param("nr_cpus", nrcpus);
507
508static int __init maxcpus(char *str)
509{
510 get_option(&str, &setup_max_cpus);
511 if (setup_max_cpus == 0)
512 arch_disable_smp_support();
513
514 return 0;
515}
516
517early_param("maxcpus", maxcpus);
518
519/* Setup number of possible processor ids */
520int nr_cpu_ids __read_mostly = NR_CPUS;
521EXPORT_SYMBOL(nr_cpu_ids);
522
523/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
524void __init setup_nr_cpu_ids(void)
525{
526 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
527}
528
529void __weak smp_announce(void)
530{
531 printk(KERN_INFO "Brought up %d CPUs\n", num_online_cpus());
532}
533
534/* Called by boot processor to activate the rest. */
535void __init smp_init(void)
536{
537 unsigned int cpu;
538
539 idle_threads_init();
540
541 /* FIXME: This should be done in userspace --RR */
542 for_each_present_cpu(cpu) {
543 if (num_online_cpus() >= setup_max_cpus)
544 break;
545 if (!cpu_online(cpu))
546 cpu_up(cpu);
547 }
548
549 /* Any cleanup work */
550 smp_announce();
551 smp_cpus_done(setup_max_cpus);
552}
553
554/*
555 * Call a function on all processors. May be used during early boot while
556 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
557 * of local_irq_disable/enable().
558 */
559int on_each_cpu(void (*func) (void *info), void *info, int wait)
560{
561 unsigned long flags;
562 int ret = 0;
563
564 preempt_disable();
565 ret = smp_call_function(func, info, wait);
566 local_irq_save(flags);
567 func(info);
568 local_irq_restore(flags);
569 preempt_enable();
570 return ret;
571}
572EXPORT_SYMBOL(on_each_cpu);
573
574/**
575 * on_each_cpu_mask(): Run a function on processors specified by
576 * cpumask, which may include the local processor.
577 * @mask: The set of cpus to run on (only runs on online subset).
578 * @func: The function to run. This must be fast and non-blocking.
579 * @info: An arbitrary pointer to pass to the function.
580 * @wait: If true, wait (atomically) until function has completed
581 * on other CPUs.
582 *
583 * If @wait is true, then returns once @func has returned.
584 *
585 * You must not call this function with disabled interrupts or from a
586 * hardware interrupt handler or from a bottom half handler. The
587 * exception is that it may be used during early boot while
588 * early_boot_irqs_disabled is set.
589 */
590void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
591 void *info, bool wait)
592{
593 int cpu = get_cpu();
594
595 smp_call_function_many(mask, func, info, wait);
596 if (cpumask_test_cpu(cpu, mask)) {
597 unsigned long flags;
598 local_irq_save(flags);
599 func(info);
600 local_irq_restore(flags);
601 }
602 put_cpu();
603}
604EXPORT_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 */
633void 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}
665EXPORT_SYMBOL(on_each_cpu_cond);
666
667static 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 */
682void 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}
688EXPORT_SYMBOL_GPL(kick_all_cpus_sync);