2 * Generic helpers for smp ipi calls
4 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
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>
23 struct call_function_data {
24 struct call_single_data __percpu *csd;
25 cpumask_var_t cpumask;
28 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
30 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
33 hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
35 long cpu = (long)hcpu;
36 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
40 case CPU_UP_PREPARE_FROZEN:
41 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
43 return notifier_from_errno(-ENOMEM);
44 cfd->csd = alloc_percpu(struct call_single_data);
46 free_cpumask_var(cfd->cpumask);
47 return notifier_from_errno(-ENOMEM);
51 #ifdef CONFIG_HOTPLUG_CPU
53 case CPU_UP_CANCELED_FROZEN:
57 free_cpumask_var(cfd->cpumask);
58 free_percpu(cfd->csd);
66 static struct notifier_block hotplug_cfd_notifier = {
67 .notifier_call = hotplug_cfd,
70 void __init call_function_init(void)
72 void *cpu = (void *)(long)smp_processor_id();
75 for_each_possible_cpu(i)
76 init_llist_head(&per_cpu(call_single_queue, i));
78 hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
79 register_cpu_notifier(&hotplug_cfd_notifier);
83 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
85 * For non-synchronous ipi calls the csd can still be in use by the
86 * previous function call. For multi-cpu calls its even more interesting
87 * as we'll have to ensure no other cpu is observing our csd.
89 static void csd_lock_wait(struct call_single_data *csd)
91 while (csd->flags & CSD_FLAG_LOCK)
95 static void csd_lock(struct call_single_data *csd)
98 csd->flags |= CSD_FLAG_LOCK;
101 * prevent CPU from reordering the above assignment
102 * to ->flags with any subsequent assignments to other
103 * fields of the specified call_single_data structure:
108 static void csd_unlock(struct call_single_data *csd)
110 WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
113 * ensure we're all done before releasing data:
117 csd->flags &= ~CSD_FLAG_LOCK;
120 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
123 * Insert a previously allocated call_single_data element
124 * for execution on the given CPU. data must already have
125 * ->func, ->info, and ->flags set.
127 static int generic_exec_single(int cpu, struct call_single_data *csd,
128 smp_call_func_t func, void *info, int wait)
130 struct call_single_data csd_stack = { .flags = 0 };
134 if (cpu == smp_processor_id()) {
135 local_irq_save(flags);
137 local_irq_restore(flags);
142 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu))
149 csd = &__get_cpu_var(csd_data);
158 csd->flags |= CSD_FLAG_WAIT;
161 * The list addition should be visible before sending the IPI
162 * handler locks the list to pull the entry off it because of
163 * normal cache coherency rules implied by spinlocks.
165 * If IPIs can go out of order to the cache coherency protocol
166 * in an architecture, sufficient synchronisation should be added
167 * to arch code to make it appear to obey cache coherency WRT
168 * locking and barrier primitives. Generic code isn't really
169 * equipped to do the right thing...
171 if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
172 arch_send_call_function_single_ipi(cpu);
181 * Invoked by arch to handle an IPI for call function single. Must be
182 * called from the arch with interrupts disabled.
184 void generic_smp_call_function_single_interrupt(void)
186 struct llist_node *entry;
187 struct call_single_data *csd, *csd_next;
190 * Shouldn't receive this interrupt on a cpu that is not yet online.
192 WARN_ON_ONCE(!cpu_online(smp_processor_id()));
194 entry = llist_del_all(&__get_cpu_var(call_single_queue));
195 entry = llist_reverse_order(entry);
197 llist_for_each_entry_safe(csd, csd_next, entry, llist) {
198 csd->func(csd->info);
204 * smp_call_function_single - Run a function on a specific CPU
205 * @func: The function to run. This must be fast and non-blocking.
206 * @info: An arbitrary pointer to pass to the function.
207 * @wait: If true, wait until function has completed on other CPUs.
209 * Returns 0 on success, else a negative status code.
211 int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
218 * prevent preemption and reschedule on another processor,
219 * as well as CPU removal
221 this_cpu = get_cpu();
224 * Can deadlock when called with interrupts disabled.
225 * We allow cpu's that are not yet online though, as no one else can
226 * send smp call function interrupt to this cpu and as such deadlocks
229 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
230 && !oops_in_progress);
232 err = generic_exec_single(cpu, NULL, func, info, wait);
238 EXPORT_SYMBOL(smp_call_function_single);
241 * smp_call_function_any - Run a function on any of the given cpus
242 * @mask: The mask of cpus it can run on.
243 * @func: The function to run. This must be fast and non-blocking.
244 * @info: An arbitrary pointer to pass to the function.
245 * @wait: If true, wait until function has completed.
247 * Returns 0 on success, else a negative status code (if no cpus were online).
249 * Selection preference:
250 * 1) current cpu if in @mask
251 * 2) any cpu of current node if in @mask
252 * 3) any other online cpu in @mask
254 int smp_call_function_any(const struct cpumask *mask,
255 smp_call_func_t func, void *info, int wait)
258 const struct cpumask *nodemask;
261 /* Try for same CPU (cheapest) */
263 if (cpumask_test_cpu(cpu, mask))
266 /* Try for same node. */
267 nodemask = cpumask_of_node(cpu_to_node(cpu));
268 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
269 cpu = cpumask_next_and(cpu, nodemask, mask)) {
274 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
275 cpu = cpumask_any_and(mask, cpu_online_mask);
277 ret = smp_call_function_single(cpu, func, info, wait);
281 EXPORT_SYMBOL_GPL(smp_call_function_any);
284 * __smp_call_function_single(): Run a function on a specific CPU
285 * @cpu: The CPU to run on.
286 * @csd: Pre-allocated and setup data structure
287 * @wait: If true, wait until function has completed on specified CPU.
289 * Like smp_call_function_single(), but allow caller to pass in a
290 * pre-allocated data structure. Useful for embedding @data inside
291 * other structures, for instance.
293 int __smp_call_function_single(int cpu, struct call_single_data *csd, int wait)
298 this_cpu = get_cpu();
300 * Can deadlock when called with interrupts disabled.
301 * We allow cpu's that are not yet online though, as no one else can
302 * send smp call function interrupt to this cpu and as such deadlocks
305 WARN_ON_ONCE(cpu_online(this_cpu) && wait && irqs_disabled()
306 && !oops_in_progress);
308 err = generic_exec_single(cpu, csd, csd->func, csd->info, wait);
313 EXPORT_SYMBOL_GPL(__smp_call_function_single);
316 * smp_call_function_many(): Run a function on a set of other CPUs.
317 * @mask: The set of cpus to run on (only runs on online subset).
318 * @func: The function to run. This must be fast and non-blocking.
319 * @info: An arbitrary pointer to pass to the function.
320 * @wait: If true, wait (atomically) until function has completed
323 * If @wait is true, then returns once @func has returned.
325 * You must not call this function with disabled interrupts or from a
326 * hardware interrupt handler or from a bottom half handler. Preemption
327 * must be disabled when calling this function.
329 void smp_call_function_many(const struct cpumask *mask,
330 smp_call_func_t func, void *info, bool wait)
332 struct call_function_data *cfd;
333 int cpu, next_cpu, this_cpu = smp_processor_id();
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
341 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
342 && !oops_in_progress && !early_boot_irqs_disabled);
344 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
345 cpu = cpumask_first_and(mask, cpu_online_mask);
347 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
349 /* No online cpus? We're done. */
350 if (cpu >= nr_cpu_ids)
353 /* Do we have another CPU which isn't us? */
354 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
355 if (next_cpu == this_cpu)
356 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
358 /* Fastpath: do that cpu by itself. */
359 if (next_cpu >= nr_cpu_ids) {
360 smp_call_function_single(cpu, func, info, wait);
364 cfd = &__get_cpu_var(cfd_data);
366 cpumask_and(cfd->cpumask, mask, cpu_online_mask);
367 cpumask_clear_cpu(this_cpu, cfd->cpumask);
369 /* Some callers race with other cpus changing the passed mask */
370 if (unlikely(!cpumask_weight(cfd->cpumask)))
373 for_each_cpu(cpu, cfd->cpumask) {
374 struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
379 llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
382 /* Send a message to all CPUs in the map */
383 arch_send_call_function_ipi_mask(cfd->cpumask);
386 for_each_cpu(cpu, cfd->cpumask) {
387 struct call_single_data *csd;
389 csd = per_cpu_ptr(cfd->csd, cpu);
394 EXPORT_SYMBOL(smp_call_function_many);
397 * smp_call_function(): Run a function on all other CPUs.
398 * @func: The function to run. This must be fast and non-blocking.
399 * @info: An arbitrary pointer to pass to the function.
400 * @wait: If true, wait (atomically) until function has completed
405 * If @wait is true, then returns once @func has returned; otherwise
406 * it returns just before the target cpu calls @func.
408 * You must not call this function with disabled interrupts or from a
409 * hardware interrupt handler or from a bottom half handler.
411 int smp_call_function(smp_call_func_t func, void *info, int wait)
414 smp_call_function_many(cpu_online_mask, func, info, wait);
419 EXPORT_SYMBOL(smp_call_function);
421 /* Setup configured maximum number of CPUs to activate */
422 unsigned int setup_max_cpus = NR_CPUS;
423 EXPORT_SYMBOL(setup_max_cpus);
427 * Setup routine for controlling SMP activation
429 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
430 * activation entirely (the MPS table probe still happens, though).
432 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
433 * greater than 0, limits the maximum number of CPUs activated in
437 void __weak arch_disable_smp_support(void) { }
439 static int __init nosmp(char *str)
442 arch_disable_smp_support();
447 early_param("nosmp", nosmp);
449 /* this is hard limit */
450 static int __init nrcpus(char *str)
454 get_option(&str, &nr_cpus);
455 if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
456 nr_cpu_ids = nr_cpus;
461 early_param("nr_cpus", nrcpus);
463 static int __init maxcpus(char *str)
465 get_option(&str, &setup_max_cpus);
466 if (setup_max_cpus == 0)
467 arch_disable_smp_support();
472 early_param("maxcpus", maxcpus);
474 /* Setup number of possible processor ids */
475 int nr_cpu_ids __read_mostly = NR_CPUS;
476 EXPORT_SYMBOL(nr_cpu_ids);
478 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
479 void __init setup_nr_cpu_ids(void)
481 nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
484 void __weak smp_announce(void)
486 printk(KERN_INFO "Brought up %d CPUs\n", num_online_cpus());
489 /* Called by boot processor to activate the rest. */
490 void __init smp_init(void)
496 /* FIXME: This should be done in userspace --RR */
497 for_each_present_cpu(cpu) {
498 if (num_online_cpus() >= setup_max_cpus)
500 if (!cpu_online(cpu))
504 /* Any cleanup work */
506 smp_cpus_done(setup_max_cpus);
510 * Call a function on all processors. May be used during early boot while
511 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
512 * of local_irq_disable/enable().
514 int on_each_cpu(void (*func) (void *info), void *info, int wait)
520 ret = smp_call_function(func, info, wait);
521 local_irq_save(flags);
523 local_irq_restore(flags);
527 EXPORT_SYMBOL(on_each_cpu);
530 * on_each_cpu_mask(): Run a function on processors specified by
531 * cpumask, which may include the local processor.
532 * @mask: The set of cpus to run on (only runs on online subset).
533 * @func: The function to run. This must be fast and non-blocking.
534 * @info: An arbitrary pointer to pass to the function.
535 * @wait: If true, wait (atomically) until function has completed
538 * If @wait is true, then returns once @func has returned.
540 * You must not call this function with disabled interrupts or from a
541 * hardware interrupt handler or from a bottom half handler. The
542 * exception is that it may be used during early boot while
543 * early_boot_irqs_disabled is set.
545 void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
546 void *info, bool wait)
550 smp_call_function_many(mask, func, info, wait);
551 if (cpumask_test_cpu(cpu, mask)) {
553 local_irq_save(flags);
555 local_irq_restore(flags);
559 EXPORT_SYMBOL(on_each_cpu_mask);
562 * on_each_cpu_cond(): Call a function on each processor for which
563 * the supplied function cond_func returns true, optionally waiting
564 * for all the required CPUs to finish. This may include the local
566 * @cond_func: A callback function that is passed a cpu id and
567 * the the info parameter. The function is called
568 * with preemption disabled. The function should
569 * return a blooean value indicating whether to IPI
571 * @func: The function to run on all applicable CPUs.
572 * This must be fast and non-blocking.
573 * @info: An arbitrary pointer to pass to both functions.
574 * @wait: If true, wait (atomically) until function has
575 * completed on other CPUs.
576 * @gfp_flags: GFP flags to use when allocating the cpumask
577 * used internally by the function.
579 * The function might sleep if the GFP flags indicates a non
580 * atomic allocation is allowed.
582 * Preemption is disabled to protect against CPUs going offline but not online.
583 * CPUs going online during the call will not be seen or sent an IPI.
585 * You must not call this function with disabled interrupts or
586 * from a hardware interrupt handler or from a bottom half handler.
588 void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
589 smp_call_func_t func, void *info, bool wait,
595 might_sleep_if(gfp_flags & __GFP_WAIT);
597 if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
599 for_each_online_cpu(cpu)
600 if (cond_func(cpu, info))
601 cpumask_set_cpu(cpu, cpus);
602 on_each_cpu_mask(cpus, func, info, wait);
604 free_cpumask_var(cpus);
607 * No free cpumask, bother. No matter, we'll
608 * just have to IPI them one by one.
611 for_each_online_cpu(cpu)
612 if (cond_func(cpu, info)) {
613 ret = smp_call_function_single(cpu, func,
620 EXPORT_SYMBOL(on_each_cpu_cond);
622 static void do_nothing(void *unused)
627 * kick_all_cpus_sync - Force all cpus out of idle
629 * Used to synchronize the update of pm_idle function pointer. It's
630 * called after the pointer is updated and returns after the dummy
631 * callback function has been executed on all cpus. The execution of
632 * the function can only happen on the remote cpus after they have
633 * left the idle function which had been called via pm_idle function
634 * pointer. So it's guaranteed that nothing uses the previous pointer
637 void kick_all_cpus_sync(void)
639 /* Make sure the change is visible before we kick the cpus */
641 smp_call_function(do_nothing, NULL, 1);
643 EXPORT_SYMBOL_GPL(kick_all_cpus_sync);