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/module.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>
17 struct list_head queue;
19 } call_function __cacheline_aligned_in_smp =
21 .queue = LIST_HEAD_INIT(call_function.queue),
22 .lock = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock),
29 struct call_function_data {
30 struct call_single_data csd;
32 cpumask_var_t cpumask;
35 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
37 struct call_single_queue {
38 struct list_head list;
42 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
45 hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
47 long cpu = (long)hcpu;
48 struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
52 case CPU_UP_PREPARE_FROZEN:
53 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
55 return notifier_from_errno(-ENOMEM);
58 #ifdef CONFIG_HOTPLUG_CPU
60 case CPU_UP_CANCELED_FROZEN:
64 free_cpumask_var(cfd->cpumask);
72 static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
73 .notifier_call = hotplug_cfd,
76 static int __cpuinit init_call_single_data(void)
78 void *cpu = (void *)(long)smp_processor_id();
81 for_each_possible_cpu(i) {
82 struct call_single_queue *q = &per_cpu(call_single_queue, i);
84 raw_spin_lock_init(&q->lock);
85 INIT_LIST_HEAD(&q->list);
88 hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
89 register_cpu_notifier(&hotplug_cfd_notifier);
93 early_initcall(init_call_single_data);
96 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
98 * For non-synchronous ipi calls the csd can still be in use by the
99 * previous function call. For multi-cpu calls its even more interesting
100 * as we'll have to ensure no other cpu is observing our csd.
102 static void csd_lock_wait(struct call_single_data *data)
104 while (data->flags & CSD_FLAG_LOCK)
108 static void csd_lock(struct call_single_data *data)
111 data->flags = CSD_FLAG_LOCK;
114 * prevent CPU from reordering the above assignment
115 * to ->flags with any subsequent assignments to other
116 * fields of the specified call_single_data structure:
121 static void csd_unlock(struct call_single_data *data)
123 WARN_ON(!(data->flags & CSD_FLAG_LOCK));
126 * ensure we're all done before releasing data:
130 data->flags &= ~CSD_FLAG_LOCK;
134 * Insert a previously allocated call_single_data element
135 * for execution on the given CPU. data must already have
136 * ->func, ->info, and ->flags set.
139 void generic_exec_single(int cpu, struct call_single_data *data, int wait)
141 struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
145 raw_spin_lock_irqsave(&dst->lock, flags);
146 ipi = list_empty(&dst->list);
147 list_add_tail(&data->list, &dst->list);
148 raw_spin_unlock_irqrestore(&dst->lock, flags);
151 * The list addition should be visible before sending the IPI
152 * handler locks the list to pull the entry off it because of
153 * normal cache coherency rules implied by spinlocks.
155 * If IPIs can go out of order to the cache coherency protocol
156 * in an architecture, sufficient synchronisation should be added
157 * to arch code to make it appear to obey cache coherency WRT
158 * locking and barrier primitives. Generic code isn't really
159 * equipped to do the right thing...
162 arch_send_call_function_single_ipi(cpu);
169 * Invoked by arch to handle an IPI for call function. Must be called with
170 * interrupts disabled.
172 void generic_smp_call_function_interrupt(void)
174 struct call_function_data *data;
175 int cpu = smp_processor_id();
178 * Shouldn't receive this interrupt on a cpu that is not yet online.
180 WARN_ON_ONCE(!cpu_online(cpu));
183 * Ensure entry is visible on call_function_queue after we have
184 * entered the IPI. See comment in smp_call_function_many.
185 * If we don't have this, then we may miss an entry on the list
186 * and never get another IPI to process it.
191 * It's ok to use list_for_each_rcu() here even though we may
192 * delete 'pos', since list_del_rcu() doesn't clear ->next
194 list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
198 * Since we walk the list without any locks, we might
199 * see an entry that was completed, removed from the
200 * list and is in the process of being reused.
202 * We must check that the cpu is in the cpumask before
203 * checking the refs, and both must be set before
204 * executing the callback on this cpu.
207 if (!cpumask_test_cpu(cpu, data->cpumask))
212 if (atomic_read(&data->refs) == 0)
215 if (!cpumask_test_and_clear_cpu(cpu, data->cpumask))
218 data->csd.func(data->csd.info);
220 refs = atomic_dec_return(&data->refs);
223 raw_spin_lock(&call_function.lock);
224 list_del_rcu(&data->csd.list);
225 raw_spin_unlock(&call_function.lock);
231 csd_unlock(&data->csd);
237 * Invoked by arch to handle an IPI for call function single. Must be
238 * called from the arch with interrupts disabled.
240 void generic_smp_call_function_single_interrupt(void)
242 struct call_single_queue *q = &__get_cpu_var(call_single_queue);
243 unsigned int data_flags;
247 * Shouldn't receive this interrupt on a cpu that is not yet online.
249 WARN_ON_ONCE(!cpu_online(smp_processor_id()));
251 raw_spin_lock(&q->lock);
252 list_replace_init(&q->list, &list);
253 raw_spin_unlock(&q->lock);
255 while (!list_empty(&list)) {
256 struct call_single_data *data;
258 data = list_entry(list.next, struct call_single_data, list);
259 list_del(&data->list);
262 * 'data' can be invalid after this call if flags == 0
263 * (when called through generic_exec_single()),
264 * so save them away before making the call:
266 data_flags = data->flags;
268 data->func(data->info);
271 * Unlocked CSDs are valid through generic_exec_single():
273 if (data_flags & CSD_FLAG_LOCK)
278 static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
281 * smp_call_function_single - Run a function on a specific CPU
282 * @func: The function to run. This must be fast and non-blocking.
283 * @info: An arbitrary pointer to pass to the function.
284 * @wait: If true, wait until function has completed on other CPUs.
286 * Returns 0 on success, else a negative status code.
288 int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
291 struct call_single_data d = {
299 * prevent preemption and reschedule on another processor,
300 * as well as CPU removal
302 this_cpu = get_cpu();
305 * Can deadlock when called with interrupts disabled.
306 * We allow cpu's that are not yet online though, as no one else can
307 * send smp call function interrupt to this cpu and as such deadlocks
310 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
311 && !oops_in_progress);
313 if (cpu == this_cpu) {
314 local_irq_save(flags);
316 local_irq_restore(flags);
318 if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
319 struct call_single_data *data = &d;
322 data = &__get_cpu_var(csd_data);
328 generic_exec_single(cpu, data, wait);
330 err = -ENXIO; /* CPU not online */
338 EXPORT_SYMBOL(smp_call_function_single);
341 * smp_call_function_any - Run a function on any of the given cpus
342 * @mask: The mask of cpus it can run on.
343 * @func: The function to run. This must be fast and non-blocking.
344 * @info: An arbitrary pointer to pass to the function.
345 * @wait: If true, wait until function has completed.
347 * Returns 0 on success, else a negative status code (if no cpus were online).
348 * Note that @wait will be implicitly turned on in case of allocation failures,
349 * since we fall back to on-stack allocation.
351 * Selection preference:
352 * 1) current cpu if in @mask
353 * 2) any cpu of current node if in @mask
354 * 3) any other online cpu in @mask
356 int smp_call_function_any(const struct cpumask *mask,
357 void (*func)(void *info), void *info, int wait)
360 const struct cpumask *nodemask;
363 /* Try for same CPU (cheapest) */
365 if (cpumask_test_cpu(cpu, mask))
368 /* Try for same node. */
369 nodemask = cpumask_of_node(cpu_to_node(cpu));
370 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
371 cpu = cpumask_next_and(cpu, nodemask, mask)) {
376 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
377 cpu = cpumask_any_and(mask, cpu_online_mask);
379 ret = smp_call_function_single(cpu, func, info, wait);
383 EXPORT_SYMBOL_GPL(smp_call_function_any);
386 * __smp_call_function_single(): Run a function on another CPU
387 * @cpu: The CPU to run on.
388 * @data: Pre-allocated and setup data structure
390 * Like smp_call_function_single(), but allow caller to pass in a
391 * pre-allocated data structure. Useful for embedding @data inside
392 * other structures, for instance.
394 void __smp_call_function_single(int cpu, struct call_single_data *data,
400 * Can deadlock when called with interrupts disabled.
401 * We allow cpu's that are not yet online though, as no one else can
402 * send smp call function interrupt to this cpu and as such deadlocks
405 WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
406 && !oops_in_progress);
408 generic_exec_single(cpu, data, wait);
412 * smp_call_function_many(): Run a function on a set of other CPUs.
413 * @mask: The set of cpus to run on (only runs on online subset).
414 * @func: The function to run. This must be fast and non-blocking.
415 * @info: An arbitrary pointer to pass to the function.
416 * @wait: If true, wait (atomically) until function has completed
419 * If @wait is true, then returns once @func has returned.
421 * You must not call this function with disabled interrupts or from a
422 * hardware interrupt handler or from a bottom half handler. Preemption
423 * must be disabled when calling this function.
425 void smp_call_function_many(const struct cpumask *mask,
426 void (*func)(void *), void *info, bool wait)
428 struct call_function_data *data;
430 int cpu, next_cpu, this_cpu = smp_processor_id();
433 * Can deadlock when called with interrupts disabled.
434 * We allow cpu's that are not yet online though, as no one else can
435 * send smp call function interrupt to this cpu and as such deadlocks
438 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
439 && !oops_in_progress);
441 /* So, what's a CPU they want? Ignoring this one. */
442 cpu = cpumask_first_and(mask, cpu_online_mask);
444 cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
446 /* No online cpus? We're done. */
447 if (cpu >= nr_cpu_ids)
450 /* Do we have another CPU which isn't us? */
451 next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
452 if (next_cpu == this_cpu)
453 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
455 /* Fastpath: do that cpu by itself. */
456 if (next_cpu >= nr_cpu_ids) {
457 smp_call_function_single(cpu, func, info, wait);
461 data = &__get_cpu_var(cfd_data);
462 csd_lock(&data->csd);
463 BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask));
465 data->csd.func = func;
466 data->csd.info = info;
467 cpumask_and(data->cpumask, mask, cpu_online_mask);
468 cpumask_clear_cpu(this_cpu, data->cpumask);
471 * We reuse the call function data without waiting for any grace
472 * period after some other cpu removes it from the global queue.
473 * This means a cpu might find our data block as it is writen.
474 * The interrupt handler waits until it sees refs filled out
475 * while its cpu mask bit is set; here we may only clear our
476 * own cpu mask bit, and must wait to set refs until we are sure
477 * previous writes are complete and we have obtained the lock to
478 * add the element to the queue.
481 raw_spin_lock_irqsave(&call_function.lock, flags);
483 * Place entry at the _HEAD_ of the list, so that any cpu still
484 * observing the entry in generic_smp_call_function_interrupt()
485 * will not miss any other list entries:
487 list_add_rcu(&data->csd.list, &call_function.queue);
489 * We rely on the wmb() in list_add_rcu to order the writes
490 * to func, data, and cpumask before this write to refs.
492 atomic_set(&data->refs, cpumask_weight(data->cpumask));
493 raw_spin_unlock_irqrestore(&call_function.lock, flags);
496 * Make the list addition visible before sending the ipi.
497 * (IPIs must obey or appear to obey normal Linux cache
498 * coherency rules -- see comment in generic_exec_single).
502 /* Send a message to all CPUs in the map */
503 arch_send_call_function_ipi_mask(data->cpumask);
505 /* Optionally wait for the CPUs to complete */
507 csd_lock_wait(&data->csd);
509 EXPORT_SYMBOL(smp_call_function_many);
512 * smp_call_function(): Run a function on all other CPUs.
513 * @func: The function to run. This must be fast and non-blocking.
514 * @info: An arbitrary pointer to pass to the function.
515 * @wait: If true, wait (atomically) until function has completed
520 * If @wait is true, then returns once @func has returned; otherwise
521 * it returns just before the target cpu calls @func.
523 * You must not call this function with disabled interrupts or from a
524 * hardware interrupt handler or from a bottom half handler.
526 int smp_call_function(void (*func)(void *), void *info, int wait)
529 smp_call_function_many(cpu_online_mask, func, info, wait);
534 EXPORT_SYMBOL(smp_call_function);
536 void ipi_call_lock(void)
538 raw_spin_lock(&call_function.lock);
541 void ipi_call_unlock(void)
543 raw_spin_unlock(&call_function.lock);
546 void ipi_call_lock_irq(void)
548 raw_spin_lock_irq(&call_function.lock);
551 void ipi_call_unlock_irq(void)
553 raw_spin_unlock_irq(&call_function.lock);