2 * Generic helpers for smp ipi calls
4 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
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>
22 CSD_FLAG_SYNCHRONOUS
= 0x02,
25 struct call_function_data
{
26 struct call_single_data __percpu
*csd
;
27 cpumask_var_t cpumask
;
30 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data
, cfd_data
);
32 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head
, call_single_queue
);
34 static void flush_smp_call_function_queue(bool warn_cpu_offline
);
37 hotplug_cfd(struct notifier_block
*nfb
, unsigned long action
, void *hcpu
)
39 long cpu
= (long)hcpu
;
40 struct call_function_data
*cfd
= &per_cpu(cfd_data
, cpu
);
44 case CPU_UP_PREPARE_FROZEN
:
45 if (!zalloc_cpumask_var_node(&cfd
->cpumask
, GFP_KERNEL
,
47 return notifier_from_errno(-ENOMEM
);
48 cfd
->csd
= alloc_percpu(struct call_single_data
);
50 free_cpumask_var(cfd
->cpumask
);
51 return notifier_from_errno(-ENOMEM
);
55 #ifdef CONFIG_HOTPLUG_CPU
57 case CPU_UP_CANCELED_FROZEN
:
58 /* Fall-through to the CPU_DEAD[_FROZEN] case. */
62 free_cpumask_var(cfd
->cpumask
);
63 free_percpu(cfd
->csd
);
67 case CPU_DYING_FROZEN
:
69 * The IPIs for the smp-call-function callbacks queued by other
70 * CPUs might arrive late, either due to hardware latencies or
71 * because this CPU disabled interrupts (inside stop-machine)
72 * before the IPIs were sent. So flush out any pending callbacks
73 * explicitly (without waiting for the IPIs to arrive), to
74 * ensure that the outgoing CPU doesn't go offline with work
77 flush_smp_call_function_queue(false);
85 static struct notifier_block hotplug_cfd_notifier
= {
86 .notifier_call
= hotplug_cfd
,
89 void __init
call_function_init(void)
91 void *cpu
= (void *)(long)smp_processor_id();
94 for_each_possible_cpu(i
)
95 init_llist_head(&per_cpu(call_single_queue
, i
));
97 hotplug_cfd(&hotplug_cfd_notifier
, CPU_UP_PREPARE
, cpu
);
98 register_cpu_notifier(&hotplug_cfd_notifier
);
102 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
104 * For non-synchronous ipi calls the csd can still be in use by the
105 * previous function call. For multi-cpu calls its even more interesting
106 * as we'll have to ensure no other cpu is observing our csd.
108 static void csd_lock_wait(struct call_single_data
*csd
)
110 while (smp_load_acquire(&csd
->flags
) & CSD_FLAG_LOCK
)
114 static void csd_lock(struct call_single_data
*csd
)
117 csd
->flags
|= CSD_FLAG_LOCK
;
120 * prevent CPU from reordering the above assignment
121 * to ->flags with any subsequent assignments to other
122 * fields of the specified call_single_data structure:
127 static void csd_unlock(struct call_single_data
*csd
)
129 WARN_ON(!(csd
->flags
& CSD_FLAG_LOCK
));
132 * ensure we're all done before releasing data:
134 smp_store_release(&csd
->flags
, 0);
137 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data
, csd_data
);
140 * Insert a previously allocated call_single_data element
141 * for execution on the given CPU. data must already have
142 * ->func, ->info, and ->flags set.
144 static int generic_exec_single(int cpu
, struct call_single_data
*csd
,
145 smp_call_func_t func
, void *info
)
147 if (cpu
== smp_processor_id()) {
151 * We can unlock early even for the synchronous on-stack case,
152 * since we're doing this from the same CPU..
155 local_irq_save(flags
);
157 local_irq_restore(flags
);
162 if ((unsigned)cpu
>= nr_cpu_ids
|| !cpu_online(cpu
))
169 * The list addition should be visible before sending the IPI
170 * handler locks the list to pull the entry off it because of
171 * normal cache coherency rules implied by spinlocks.
173 * If IPIs can go out of order to the cache coherency protocol
174 * in an architecture, sufficient synchronisation should be added
175 * to arch code to make it appear to obey cache coherency WRT
176 * locking and barrier primitives. Generic code isn't really
177 * equipped to do the right thing...
179 if (llist_add(&csd
->llist
, &per_cpu(call_single_queue
, cpu
)))
180 arch_send_call_function_single_ipi(cpu
);
186 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
188 * Invoked by arch to handle an IPI for call function single.
189 * Must be called with interrupts disabled.
191 void generic_smp_call_function_single_interrupt(void)
193 flush_smp_call_function_queue(true);
197 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
199 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
200 * offline CPU. Skip this check if set to 'false'.
202 * Flush any pending smp-call-function callbacks queued on this CPU. This is
203 * invoked by the generic IPI handler, as well as by a CPU about to go offline,
204 * to ensure that all pending IPI callbacks are run before it goes completely
207 * Loop through the call_single_queue and run all the queued callbacks.
208 * Must be called with interrupts disabled.
210 static void flush_smp_call_function_queue(bool warn_cpu_offline
)
212 struct llist_head
*head
;
213 struct llist_node
*entry
;
214 struct call_single_data
*csd
, *csd_next
;
217 WARN_ON(!irqs_disabled());
219 head
= this_cpu_ptr(&call_single_queue
);
220 entry
= llist_del_all(head
);
221 entry
= llist_reverse_order(entry
);
223 /* There shouldn't be any pending callbacks on an offline CPU. */
224 if (unlikely(warn_cpu_offline
&& !cpu_online(smp_processor_id()) &&
225 !warned
&& !llist_empty(head
))) {
227 WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
230 * We don't have to use the _safe() variant here
231 * because we are not invoking the IPI handlers yet.
233 llist_for_each_entry(csd
, entry
, llist
)
234 pr_warn("IPI callback %pS sent to offline CPU\n",
238 llist_for_each_entry_safe(csd
, csd_next
, entry
, llist
) {
239 smp_call_func_t func
= csd
->func
;
240 void *info
= csd
->info
;
242 /* Do we wait until *after* callback? */
243 if (csd
->flags
& CSD_FLAG_SYNCHRONOUS
) {
253 * Handle irq works queued remotely by irq_work_queue_on().
254 * Smp functions above are typically synchronous so they
255 * better run first since some other CPUs may be busy waiting
262 * smp_call_function_single - Run a function on a specific CPU
263 * @func: The function to run. This must be fast and non-blocking.
264 * @info: An arbitrary pointer to pass to the function.
265 * @wait: If true, wait until function has completed on other CPUs.
267 * Returns 0 on success, else a negative status code.
269 int smp_call_function_single(int cpu
, smp_call_func_t func
, void *info
,
272 struct call_single_data
*csd
;
273 struct call_single_data csd_stack
= { .flags
= CSD_FLAG_LOCK
| CSD_FLAG_SYNCHRONOUS
};
278 * prevent preemption and reschedule on another processor,
279 * as well as CPU removal
281 this_cpu
= get_cpu();
284 * Can deadlock when called with interrupts disabled.
285 * We allow cpu's that are not yet online though, as no one else can
286 * send smp call function interrupt to this cpu and as such deadlocks
289 WARN_ON_ONCE(cpu_online(this_cpu
) && irqs_disabled()
290 && !oops_in_progress
);
294 csd
= this_cpu_ptr(&csd_data
);
298 err
= generic_exec_single(cpu
, csd
, func
, info
);
307 EXPORT_SYMBOL(smp_call_function_single
);
310 * smp_call_function_single_async(): Run an asynchronous function on a
312 * @cpu: The CPU to run on.
313 * @csd: Pre-allocated and setup data structure
315 * Like smp_call_function_single(), but the call is asynchonous and
316 * can thus be done from contexts with disabled interrupts.
318 * The caller passes his own pre-allocated data structure
319 * (ie: embedded in an object) and is responsible for synchronizing it
320 * such that the IPIs performed on the @csd are strictly serialized.
322 * NOTE: Be careful, there is unfortunately no current debugging facility to
323 * validate the correctness of this serialization.
325 int smp_call_function_single_async(int cpu
, struct call_single_data
*csd
)
331 /* We could deadlock if we have to wait here with interrupts disabled! */
332 if (WARN_ON_ONCE(csd
->flags
& CSD_FLAG_LOCK
))
335 csd
->flags
= CSD_FLAG_LOCK
;
338 err
= generic_exec_single(cpu
, csd
, csd
->func
, csd
->info
);
343 EXPORT_SYMBOL_GPL(smp_call_function_single_async
);
346 * smp_call_function_any - Run a function on any of the given cpus
347 * @mask: The mask of cpus it can run on.
348 * @func: The function to run. This must be fast and non-blocking.
349 * @info: An arbitrary pointer to pass to the function.
350 * @wait: If true, wait until function has completed.
352 * Returns 0 on success, else a negative status code (if no cpus were online).
354 * Selection preference:
355 * 1) current cpu if in @mask
356 * 2) any cpu of current node if in @mask
357 * 3) any other online cpu in @mask
359 int smp_call_function_any(const struct cpumask
*mask
,
360 smp_call_func_t func
, void *info
, int wait
)
363 const struct cpumask
*nodemask
;
366 /* Try for same CPU (cheapest) */
368 if (cpumask_test_cpu(cpu
, mask
))
371 /* Try for same node. */
372 nodemask
= cpumask_of_node(cpu_to_node(cpu
));
373 for (cpu
= cpumask_first_and(nodemask
, mask
); cpu
< nr_cpu_ids
;
374 cpu
= cpumask_next_and(cpu
, nodemask
, mask
)) {
379 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
380 cpu
= cpumask_any_and(mask
, cpu_online_mask
);
382 ret
= smp_call_function_single(cpu
, func
, info
, wait
);
386 EXPORT_SYMBOL_GPL(smp_call_function_any
);
389 * smp_call_function_many(): Run a function on a set of other CPUs.
390 * @mask: The set of cpus to run on (only runs on online subset).
391 * @func: The function to run. This must be fast and non-blocking.
392 * @info: An arbitrary pointer to pass to the function.
393 * @wait: If true, wait (atomically) until function has completed
396 * If @wait is true, then returns once @func has returned.
398 * You must not call this function with disabled interrupts or from a
399 * hardware interrupt handler or from a bottom half handler. Preemption
400 * must be disabled when calling this function.
402 void smp_call_function_many(const struct cpumask
*mask
,
403 smp_call_func_t func
, void *info
, bool wait
)
405 struct call_function_data
*cfd
;
406 int cpu
, next_cpu
, this_cpu
= smp_processor_id();
409 * Can deadlock when called with interrupts disabled.
410 * We allow cpu's that are not yet online though, as no one else can
411 * send smp call function interrupt to this cpu and as such deadlocks
414 WARN_ON_ONCE(cpu_online(this_cpu
) && irqs_disabled()
415 && !oops_in_progress
&& !early_boot_irqs_disabled
);
417 /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
418 cpu
= cpumask_first_and(mask
, cpu_online_mask
);
420 cpu
= cpumask_next_and(cpu
, mask
, cpu_online_mask
);
422 /* No online cpus? We're done. */
423 if (cpu
>= nr_cpu_ids
)
426 /* Do we have another CPU which isn't us? */
427 next_cpu
= cpumask_next_and(cpu
, mask
, cpu_online_mask
);
428 if (next_cpu
== this_cpu
)
429 next_cpu
= cpumask_next_and(next_cpu
, mask
, cpu_online_mask
);
431 /* Fastpath: do that cpu by itself. */
432 if (next_cpu
>= nr_cpu_ids
) {
433 smp_call_function_single(cpu
, func
, info
, wait
);
437 cfd
= this_cpu_ptr(&cfd_data
);
439 cpumask_and(cfd
->cpumask
, mask
, cpu_online_mask
);
440 cpumask_clear_cpu(this_cpu
, cfd
->cpumask
);
442 /* Some callers race with other cpus changing the passed mask */
443 if (unlikely(!cpumask_weight(cfd
->cpumask
)))
446 for_each_cpu(cpu
, cfd
->cpumask
) {
447 struct call_single_data
*csd
= per_cpu_ptr(cfd
->csd
, cpu
);
451 csd
->flags
|= CSD_FLAG_SYNCHRONOUS
;
454 llist_add(&csd
->llist
, &per_cpu(call_single_queue
, cpu
));
457 /* Send a message to all CPUs in the map */
458 arch_send_call_function_ipi_mask(cfd
->cpumask
);
461 for_each_cpu(cpu
, cfd
->cpumask
) {
462 struct call_single_data
*csd
;
464 csd
= per_cpu_ptr(cfd
->csd
, cpu
);
469 EXPORT_SYMBOL(smp_call_function_many
);
472 * smp_call_function(): Run a function on all other CPUs.
473 * @func: The function to run. This must be fast and non-blocking.
474 * @info: An arbitrary pointer to pass to the function.
475 * @wait: If true, wait (atomically) until function has completed
480 * If @wait is true, then returns once @func has returned; otherwise
481 * it returns just before the target cpu calls @func.
483 * You must not call this function with disabled interrupts or from a
484 * hardware interrupt handler or from a bottom half handler.
486 int smp_call_function(smp_call_func_t func
, void *info
, int wait
)
489 smp_call_function_many(cpu_online_mask
, func
, info
, wait
);
494 EXPORT_SYMBOL(smp_call_function
);
496 /* Setup configured maximum number of CPUs to activate */
497 unsigned int setup_max_cpus
= NR_CPUS
;
498 EXPORT_SYMBOL(setup_max_cpus
);
502 * Setup routine for controlling SMP activation
504 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
505 * activation entirely (the MPS table probe still happens, though).
507 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
508 * greater than 0, limits the maximum number of CPUs activated in
512 void __weak
arch_disable_smp_support(void) { }
514 static int __init
nosmp(char *str
)
517 arch_disable_smp_support();
522 early_param("nosmp", nosmp
);
524 /* this is hard limit */
525 static int __init
nrcpus(char *str
)
529 get_option(&str
, &nr_cpus
);
530 if (nr_cpus
> 0 && nr_cpus
< nr_cpu_ids
)
531 nr_cpu_ids
= nr_cpus
;
536 early_param("nr_cpus", nrcpus
);
538 static int __init
maxcpus(char *str
)
540 get_option(&str
, &setup_max_cpus
);
541 if (setup_max_cpus
== 0)
542 arch_disable_smp_support();
547 early_param("maxcpus", maxcpus
);
549 /* Setup number of possible processor ids */
550 int nr_cpu_ids __read_mostly
= NR_CPUS
;
551 EXPORT_SYMBOL(nr_cpu_ids
);
553 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
554 void __init
setup_nr_cpu_ids(void)
556 nr_cpu_ids
= find_last_bit(cpumask_bits(cpu_possible_mask
),NR_CPUS
) + 1;
559 void __weak
smp_announce(void)
561 printk(KERN_INFO
"Brought up %d CPUs\n", num_online_cpus());
564 /* Called by boot processor to activate the rest. */
565 void __init
smp_init(void)
571 /* FIXME: This should be done in userspace --RR */
572 for_each_present_cpu(cpu
) {
573 if (num_online_cpus() >= setup_max_cpus
)
575 if (!cpu_online(cpu
))
579 /* Any cleanup work */
581 smp_cpus_done(setup_max_cpus
);
585 * Call a function on all processors. May be used during early boot while
586 * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
587 * of local_irq_disable/enable().
589 int on_each_cpu(void (*func
) (void *info
), void *info
, int wait
)
595 ret
= smp_call_function(func
, info
, wait
);
596 local_irq_save(flags
);
598 local_irq_restore(flags
);
602 EXPORT_SYMBOL(on_each_cpu
);
605 * on_each_cpu_mask(): Run a function on processors specified by
606 * cpumask, which may include the local processor.
607 * @mask: The set of cpus to run on (only runs on online subset).
608 * @func: The function to run. This must be fast and non-blocking.
609 * @info: An arbitrary pointer to pass to the function.
610 * @wait: If true, wait (atomically) until function has completed
613 * If @wait is true, then returns once @func has returned.
615 * You must not call this function with disabled interrupts or from a
616 * hardware interrupt handler or from a bottom half handler. The
617 * exception is that it may be used during early boot while
618 * early_boot_irqs_disabled is set.
620 void on_each_cpu_mask(const struct cpumask
*mask
, smp_call_func_t func
,
621 void *info
, bool wait
)
625 smp_call_function_many(mask
, func
, info
, wait
);
626 if (cpumask_test_cpu(cpu
, mask
)) {
628 local_irq_save(flags
);
630 local_irq_restore(flags
);
634 EXPORT_SYMBOL(on_each_cpu_mask
);
637 * on_each_cpu_cond(): Call a function on each processor for which
638 * the supplied function cond_func returns true, optionally waiting
639 * for all the required CPUs to finish. This may include the local
641 * @cond_func: A callback function that is passed a cpu id and
642 * the the info parameter. The function is called
643 * with preemption disabled. The function should
644 * return a blooean value indicating whether to IPI
646 * @func: The function to run on all applicable CPUs.
647 * This must be fast and non-blocking.
648 * @info: An arbitrary pointer to pass to both functions.
649 * @wait: If true, wait (atomically) until function has
650 * completed on other CPUs.
651 * @gfp_flags: GFP flags to use when allocating the cpumask
652 * used internally by the function.
654 * The function might sleep if the GFP flags indicates a non
655 * atomic allocation is allowed.
657 * Preemption is disabled to protect against CPUs going offline but not online.
658 * CPUs going online during the call will not be seen or sent an IPI.
660 * You must not call this function with disabled interrupts or
661 * from a hardware interrupt handler or from a bottom half handler.
663 void on_each_cpu_cond(bool (*cond_func
)(int cpu
, void *info
),
664 smp_call_func_t func
, void *info
, bool wait
,
670 might_sleep_if(gfp_flags
& __GFP_WAIT
);
672 if (likely(zalloc_cpumask_var(&cpus
, (gfp_flags
|__GFP_NOWARN
)))) {
674 for_each_online_cpu(cpu
)
675 if (cond_func(cpu
, info
))
676 cpumask_set_cpu(cpu
, cpus
);
677 on_each_cpu_mask(cpus
, func
, info
, wait
);
679 free_cpumask_var(cpus
);
682 * No free cpumask, bother. No matter, we'll
683 * just have to IPI them one by one.
686 for_each_online_cpu(cpu
)
687 if (cond_func(cpu
, info
)) {
688 ret
= smp_call_function_single(cpu
, func
,
695 EXPORT_SYMBOL(on_each_cpu_cond
);
697 static void do_nothing(void *unused
)
702 * kick_all_cpus_sync - Force all cpus out of idle
704 * Used to synchronize the update of pm_idle function pointer. It's
705 * called after the pointer is updated and returns after the dummy
706 * callback function has been executed on all cpus. The execution of
707 * the function can only happen on the remote cpus after they have
708 * left the idle function which had been called via pm_idle function
709 * pointer. So it's guaranteed that nothing uses the previous pointer
712 void kick_all_cpus_sync(void)
714 /* Make sure the change is visible before we kick the cpus */
716 smp_call_function(do_nothing
, NULL
, 1);
718 EXPORT_SYMBOL_GPL(kick_all_cpus_sync
);
721 * wake_up_all_idle_cpus - break all cpus out of idle
722 * wake_up_all_idle_cpus try to break all cpus which is in idle state even
723 * including idle polling cpus, for non-idle cpus, we will do nothing
726 void wake_up_all_idle_cpus(void)
731 for_each_online_cpu(cpu
) {
732 if (cpu
== smp_processor_id())
735 wake_up_if_idle(cpu
);
739 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus
);