summaryrefslogtreecommitdiff
path: root/kernel/smp.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/smp.c')
-rw-r--r--kernel/smp.c741
1 files changed, 741 insertions, 0 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
new file mode 100644
index 000000000..07854477c
--- /dev/null
+++ b/kernel/smp.c
@@ -0,0 +1,741 @@
+/*
+ * Generic helpers for smp ipi calls
+ *
+ * (C) Jens Axboe <jens.axboe@oracle.com> 2008
+ */
+#include <linux/irq_work.h>
+#include <linux/rcupdate.h>
+#include <linux/rculist.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/gfp.h>
+#include <linux/smp.h>
+#include <linux/cpu.h>
+#include <linux/sched.h>
+
+#include "smpboot.h"
+
+enum {
+ CSD_FLAG_LOCK = 0x01,
+ CSD_FLAG_SYNCHRONOUS = 0x02,
+};
+
+struct call_function_data {
+ struct call_single_data __percpu *csd;
+ cpumask_var_t cpumask;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
+
+static void flush_smp_call_function_queue(bool warn_cpu_offline);
+
+static int
+hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+ long cpu = (long)hcpu;
+ struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_UP_PREPARE_FROZEN:
+ if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
+ cpu_to_node(cpu)))
+ return notifier_from_errno(-ENOMEM);
+ cfd->csd = alloc_percpu(struct call_single_data);
+ if (!cfd->csd) {
+ free_cpumask_var(cfd->cpumask);
+ return notifier_from_errno(-ENOMEM);
+ }
+ break;
+
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_UP_CANCELED:
+ case CPU_UP_CANCELED_FROZEN:
+ /* Fall-through to the CPU_DEAD[_FROZEN] case. */
+
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ free_cpumask_var(cfd->cpumask);
+ free_percpu(cfd->csd);
+ break;
+
+ case CPU_DYING:
+ case CPU_DYING_FROZEN:
+ /*
+ * The IPIs for the smp-call-function callbacks queued by other
+ * CPUs might arrive late, either due to hardware latencies or
+ * because this CPU disabled interrupts (inside stop-machine)
+ * before the IPIs were sent. So flush out any pending callbacks
+ * explicitly (without waiting for the IPIs to arrive), to
+ * ensure that the outgoing CPU doesn't go offline with work
+ * still pending.
+ */
+ flush_smp_call_function_queue(false);
+ break;
+#endif
+ };
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block hotplug_cfd_notifier = {
+ .notifier_call = hotplug_cfd,
+};
+
+void __init call_function_init(void)
+{
+ void *cpu = (void *)(long)smp_processor_id();
+ int i;
+
+ for_each_possible_cpu(i)
+ init_llist_head(&per_cpu(call_single_queue, i));
+
+ hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
+ register_cpu_notifier(&hotplug_cfd_notifier);
+}
+
+/*
+ * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
+ *
+ * For non-synchronous ipi calls the csd can still be in use by the
+ * previous function call. For multi-cpu calls its even more interesting
+ * as we'll have to ensure no other cpu is observing our csd.
+ */
+static void csd_lock_wait(struct call_single_data *csd)
+{
+ while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
+ cpu_relax();
+}
+
+static void csd_lock(struct call_single_data *csd)
+{
+ csd_lock_wait(csd);
+ csd->flags |= CSD_FLAG_LOCK;
+
+ /*
+ * prevent CPU from reordering the above assignment
+ * to ->flags with any subsequent assignments to other
+ * fields of the specified call_single_data structure:
+ */
+ smp_wmb();
+}
+
+static void csd_unlock(struct call_single_data *csd)
+{
+ WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
+
+ /*
+ * ensure we're all done before releasing data:
+ */
+ smp_store_release(&csd->flags, 0);
+}
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
+
+/*
+ * Insert a previously allocated call_single_data element
+ * for execution on the given CPU. data must already have
+ * ->func, ->info, and ->flags set.
+ */
+static int generic_exec_single(int cpu, struct call_single_data *csd,
+ smp_call_func_t func, void *info)
+{
+ if (cpu == smp_processor_id()) {
+ unsigned long flags;
+
+ /*
+ * We can unlock early even for the synchronous on-stack case,
+ * since we're doing this from the same CPU..
+ */
+ csd_unlock(csd);
+ local_irq_save(flags);
+ func(info);
+ local_irq_restore(flags);
+ return 0;
+ }
+
+
+ if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
+ csd_unlock(csd);
+ return -ENXIO;
+ }
+
+ csd->func = func;
+ csd->info = info;
+
+ /*
+ * The list addition should be visible before sending the IPI
+ * handler locks the list to pull the entry off it because of
+ * normal cache coherency rules implied by spinlocks.
+ *
+ * If IPIs can go out of order to the cache coherency protocol
+ * in an architecture, sufficient synchronisation should be added
+ * to arch code to make it appear to obey cache coherency WRT
+ * locking and barrier primitives. Generic code isn't really
+ * equipped to do the right thing...
+ */
+ if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
+ arch_send_call_function_single_ipi(cpu);
+
+ return 0;
+}
+
+/**
+ * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks
+ *
+ * Invoked by arch to handle an IPI for call function single.
+ * Must be called with interrupts disabled.
+ */
+void generic_smp_call_function_single_interrupt(void)
+{
+ flush_smp_call_function_queue(true);
+}
+
+/**
+ * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
+ *
+ * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
+ * offline CPU. Skip this check if set to 'false'.
+ *
+ * Flush any pending smp-call-function callbacks queued on this CPU. This is
+ * invoked by the generic IPI handler, as well as by a CPU about to go offline,
+ * to ensure that all pending IPI callbacks are run before it goes completely
+ * offline.
+ *
+ * Loop through the call_single_queue and run all the queued callbacks.
+ * Must be called with interrupts disabled.
+ */
+static void flush_smp_call_function_queue(bool warn_cpu_offline)
+{
+ struct llist_head *head;
+ struct llist_node *entry;
+ struct call_single_data *csd, *csd_next;
+ static bool warned;
+
+ WARN_ON(!irqs_disabled());
+
+ head = this_cpu_ptr(&call_single_queue);
+ entry = llist_del_all(head);
+ entry = llist_reverse_order(entry);
+
+ /* There shouldn't be any pending callbacks on an offline CPU. */
+ if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
+ !warned && !llist_empty(head))) {
+ warned = true;
+ WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
+
+ /*
+ * We don't have to use the _safe() variant here
+ * because we are not invoking the IPI handlers yet.
+ */
+ llist_for_each_entry(csd, entry, llist)
+ pr_warn("IPI callback %pS sent to offline CPU\n",
+ csd->func);
+ }
+
+ llist_for_each_entry_safe(csd, csd_next, entry, llist) {
+ smp_call_func_t func = csd->func;
+ void *info = csd->info;
+
+ /* Do we wait until *after* callback? */
+ if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
+ func(info);
+ csd_unlock(csd);
+ } else {
+ csd_unlock(csd);
+ func(info);
+ }
+ }
+
+ /*
+ * Handle irq works queued remotely by irq_work_queue_on().
+ * Smp functions above are typically synchronous so they
+ * better run first since some other CPUs may be busy waiting
+ * for them.
+ */
+ irq_work_run();
+}
+
+/*
+ * smp_call_function_single - Run a function on a specific CPU
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait until function has completed on other CPUs.
+ *
+ * Returns 0 on success, else a negative status code.
+ */
+int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
+ int wait)
+{
+ struct call_single_data *csd;
+ struct call_single_data csd_stack = { .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS };
+ int this_cpu;
+ int err;
+
+ /*
+ * prevent preemption and reschedule on another processor,
+ * as well as CPU removal
+ */
+ this_cpu = get_cpu();
+
+ /*
+ * Can deadlock when called with interrupts disabled.
+ * We allow cpu's that are not yet online though, as no one else can
+ * send smp call function interrupt to this cpu and as such deadlocks
+ * can't happen.
+ */
+ WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
+ && !oops_in_progress);
+
+ csd = &csd_stack;
+ if (!wait) {
+ csd = this_cpu_ptr(&csd_data);
+ csd_lock(csd);
+ }
+
+ err = generic_exec_single(cpu, csd, func, info);
+
+ if (wait)
+ csd_lock_wait(csd);
+
+ put_cpu();
+
+ return err;
+}
+EXPORT_SYMBOL(smp_call_function_single);
+
+/**
+ * smp_call_function_single_async(): Run an asynchronous function on a
+ * specific CPU.
+ * @cpu: The CPU to run on.
+ * @csd: Pre-allocated and setup data structure
+ *
+ * Like smp_call_function_single(), but the call is asynchonous and
+ * can thus be done from contexts with disabled interrupts.
+ *
+ * The caller passes his own pre-allocated data structure
+ * (ie: embedded in an object) and is responsible for synchronizing it
+ * such that the IPIs performed on the @csd are strictly serialized.
+ *
+ * NOTE: Be careful, there is unfortunately no current debugging facility to
+ * validate the correctness of this serialization.
+ */
+int smp_call_function_single_async(int cpu, struct call_single_data *csd)
+{
+ int err = 0;
+
+ preempt_disable();
+
+ /* We could deadlock if we have to wait here with interrupts disabled! */
+ if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
+ csd_lock_wait(csd);
+
+ csd->flags = CSD_FLAG_LOCK;
+ smp_wmb();
+
+ err = generic_exec_single(cpu, csd, csd->func, csd->info);
+ preempt_enable();
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(smp_call_function_single_async);
+
+/*
+ * smp_call_function_any - Run a function on any of the given cpus
+ * @mask: The mask of cpus it can run on.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait until function has completed.
+ *
+ * Returns 0 on success, else a negative status code (if no cpus were online).
+ *
+ * Selection preference:
+ * 1) current cpu if in @mask
+ * 2) any cpu of current node if in @mask
+ * 3) any other online cpu in @mask
+ */
+int smp_call_function_any(const struct cpumask *mask,
+ smp_call_func_t func, void *info, int wait)
+{
+ unsigned int cpu;
+ const struct cpumask *nodemask;
+ int ret;
+
+ /* Try for same CPU (cheapest) */
+ cpu = get_cpu();
+ if (cpumask_test_cpu(cpu, mask))
+ goto call;
+
+ /* Try for same node. */
+ nodemask = cpumask_of_node(cpu_to_node(cpu));
+ for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
+ cpu = cpumask_next_and(cpu, nodemask, mask)) {
+ if (cpu_online(cpu))
+ goto call;
+ }
+
+ /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
+ cpu = cpumask_any_and(mask, cpu_online_mask);
+call:
+ ret = smp_call_function_single(cpu, func, info, wait);
+ put_cpu();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(smp_call_function_any);
+
+/**
+ * smp_call_function_many(): Run a function on a set of other CPUs.
+ * @mask: The set of cpus to run on (only runs on online subset).
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed
+ * on other CPUs.
+ *
+ * If @wait is true, then returns once @func has returned.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler. Preemption
+ * must be disabled when calling this function.
+ */
+void smp_call_function_many(const struct cpumask *mask,
+ smp_call_func_t func, void *info, bool wait)
+{
+ struct call_function_data *cfd;
+ int cpu, next_cpu, this_cpu = smp_processor_id();
+
+ /*
+ * Can deadlock when called with interrupts disabled.
+ * We allow cpu's that are not yet online though, as no one else can
+ * send smp call function interrupt to this cpu and as such deadlocks
+ * can't happen.
+ */
+ WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
+ && !oops_in_progress && !early_boot_irqs_disabled);
+
+ /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
+ cpu = cpumask_first_and(mask, cpu_online_mask);
+ if (cpu == this_cpu)
+ cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
+
+ /* No online cpus? We're done. */
+ if (cpu >= nr_cpu_ids)
+ return;
+
+ /* Do we have another CPU which isn't us? */
+ next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
+ if (next_cpu == this_cpu)
+ next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
+
+ /* Fastpath: do that cpu by itself. */
+ if (next_cpu >= nr_cpu_ids) {
+ smp_call_function_single(cpu, func, info, wait);
+ return;
+ }
+
+ cfd = this_cpu_ptr(&cfd_data);
+
+ cpumask_and(cfd->cpumask, mask, cpu_online_mask);
+ cpumask_clear_cpu(this_cpu, cfd->cpumask);
+
+ /* Some callers race with other cpus changing the passed mask */
+ if (unlikely(!cpumask_weight(cfd->cpumask)))
+ return;
+
+ for_each_cpu(cpu, cfd->cpumask) {
+ struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
+
+ csd_lock(csd);
+ if (wait)
+ csd->flags |= CSD_FLAG_SYNCHRONOUS;
+ csd->func = func;
+ csd->info = info;
+ llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
+ }
+
+ /* Send a message to all CPUs in the map */
+ arch_send_call_function_ipi_mask(cfd->cpumask);
+
+ if (wait) {
+ for_each_cpu(cpu, cfd->cpumask) {
+ struct call_single_data *csd;
+
+ csd = per_cpu_ptr(cfd->csd, cpu);
+ csd_lock_wait(csd);
+ }
+ }
+}
+EXPORT_SYMBOL(smp_call_function_many);
+
+/**
+ * smp_call_function(): Run a function on all other CPUs.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed
+ * on other CPUs.
+ *
+ * Returns 0.
+ *
+ * If @wait is true, then returns once @func has returned; otherwise
+ * it returns just before the target cpu calls @func.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler.
+ */
+int smp_call_function(smp_call_func_t func, void *info, int wait)
+{
+ preempt_disable();
+ smp_call_function_many(cpu_online_mask, func, info, wait);
+ preempt_enable();
+
+ return 0;
+}
+EXPORT_SYMBOL(smp_call_function);
+
+/* Setup configured maximum number of CPUs to activate */
+unsigned int setup_max_cpus = NR_CPUS;
+EXPORT_SYMBOL(setup_max_cpus);
+
+
+/*
+ * Setup routine for controlling SMP activation
+ *
+ * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
+ * activation entirely (the MPS table probe still happens, though).
+ *
+ * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
+ * greater than 0, limits the maximum number of CPUs activated in
+ * SMP mode to <NUM>.
+ */
+
+void __weak arch_disable_smp_support(void) { }
+
+static int __init nosmp(char *str)
+{
+ setup_max_cpus = 0;
+ arch_disable_smp_support();
+
+ return 0;
+}
+
+early_param("nosmp", nosmp);
+
+/* this is hard limit */
+static int __init nrcpus(char *str)
+{
+ int nr_cpus;
+
+ get_option(&str, &nr_cpus);
+ if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
+ nr_cpu_ids = nr_cpus;
+
+ return 0;
+}
+
+early_param("nr_cpus", nrcpus);
+
+static int __init maxcpus(char *str)
+{
+ get_option(&str, &setup_max_cpus);
+ if (setup_max_cpus == 0)
+ arch_disable_smp_support();
+
+ return 0;
+}
+
+early_param("maxcpus", maxcpus);
+
+/* Setup number of possible processor ids */
+int nr_cpu_ids __read_mostly = NR_CPUS;
+EXPORT_SYMBOL(nr_cpu_ids);
+
+/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
+void __init setup_nr_cpu_ids(void)
+{
+ nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
+}
+
+void __weak smp_announce(void)
+{
+ printk(KERN_INFO "Brought up %d CPUs\n", num_online_cpus());
+}
+
+/* Called by boot processor to activate the rest. */
+void __init smp_init(void)
+{
+ unsigned int cpu;
+
+ idle_threads_init();
+
+ /* FIXME: This should be done in userspace --RR */
+ for_each_present_cpu(cpu) {
+ if (num_online_cpus() >= setup_max_cpus)
+ break;
+ if (!cpu_online(cpu))
+ cpu_up(cpu);
+ }
+
+ /* Any cleanup work */
+ smp_announce();
+ smp_cpus_done(setup_max_cpus);
+}
+
+/*
+ * Call a function on all processors. May be used during early boot while
+ * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
+ * of local_irq_disable/enable().
+ */
+int on_each_cpu(void (*func) (void *info), void *info, int wait)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ preempt_disable();
+ ret = smp_call_function(func, info, wait);
+ local_irq_save(flags);
+ func(info);
+ local_irq_restore(flags);
+ preempt_enable();
+ return ret;
+}
+EXPORT_SYMBOL(on_each_cpu);
+
+/**
+ * on_each_cpu_mask(): Run a function on processors specified by
+ * cpumask, which may include the local processor.
+ * @mask: The set of cpus to run on (only runs on online subset).
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed
+ * on other CPUs.
+ *
+ * If @wait is true, then returns once @func has returned.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler. The
+ * exception is that it may be used during early boot while
+ * early_boot_irqs_disabled is set.
+ */
+void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
+ void *info, bool wait)
+{
+ int cpu = get_cpu();
+
+ smp_call_function_many(mask, func, info, wait);
+ if (cpumask_test_cpu(cpu, mask)) {
+ unsigned long flags;
+ local_irq_save(flags);
+ func(info);
+ local_irq_restore(flags);
+ }
+ put_cpu();
+}
+EXPORT_SYMBOL(on_each_cpu_mask);
+
+/*
+ * on_each_cpu_cond(): Call a function on each processor for which
+ * the supplied function cond_func returns true, optionally waiting
+ * for all the required CPUs to finish. This may include the local
+ * processor.
+ * @cond_func: A callback function that is passed a cpu id and
+ * the the info parameter. The function is called
+ * with preemption disabled. The function should
+ * return a blooean value indicating whether to IPI
+ * the specified CPU.
+ * @func: The function to run on all applicable CPUs.
+ * This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to both functions.
+ * @wait: If true, wait (atomically) until function has
+ * completed on other CPUs.
+ * @gfp_flags: GFP flags to use when allocating the cpumask
+ * used internally by the function.
+ *
+ * The function might sleep if the GFP flags indicates a non
+ * atomic allocation is allowed.
+ *
+ * Preemption is disabled to protect against CPUs going offline but not online.
+ * CPUs going online during the call will not be seen or sent an IPI.
+ *
+ * You must not call this function with disabled interrupts or
+ * from a hardware interrupt handler or from a bottom half handler.
+ */
+void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
+ smp_call_func_t func, void *info, bool wait,
+ gfp_t gfp_flags)
+{
+ cpumask_var_t cpus;
+ int cpu, ret;
+
+ might_sleep_if(gfp_flags & __GFP_WAIT);
+
+ if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
+ preempt_disable();
+ for_each_online_cpu(cpu)
+ if (cond_func(cpu, info))
+ cpumask_set_cpu(cpu, cpus);
+ on_each_cpu_mask(cpus, func, info, wait);
+ preempt_enable();
+ free_cpumask_var(cpus);
+ } else {
+ /*
+ * No free cpumask, bother. No matter, we'll
+ * just have to IPI them one by one.
+ */
+ preempt_disable();
+ for_each_online_cpu(cpu)
+ if (cond_func(cpu, info)) {
+ ret = smp_call_function_single(cpu, func,
+ info, wait);
+ WARN_ON_ONCE(ret);
+ }
+ preempt_enable();
+ }
+}
+EXPORT_SYMBOL(on_each_cpu_cond);
+
+static void do_nothing(void *unused)
+{
+}
+
+/**
+ * kick_all_cpus_sync - Force all cpus out of idle
+ *
+ * Used to synchronize the update of pm_idle function pointer. It's
+ * called after the pointer is updated and returns after the dummy
+ * callback function has been executed on all cpus. The execution of
+ * the function can only happen on the remote cpus after they have
+ * left the idle function which had been called via pm_idle function
+ * pointer. So it's guaranteed that nothing uses the previous pointer
+ * anymore.
+ */
+void kick_all_cpus_sync(void)
+{
+ /* Make sure the change is visible before we kick the cpus */
+ smp_mb();
+ smp_call_function(do_nothing, NULL, 1);
+}
+EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
+
+/**
+ * wake_up_all_idle_cpus - break all cpus out of idle
+ * wake_up_all_idle_cpus try to break all cpus which is in idle state even
+ * including idle polling cpus, for non-idle cpus, we will do nothing
+ * for them.
+ */
+void wake_up_all_idle_cpus(void)
+{
+ int cpu;
+
+ preempt_disable();
+ for_each_online_cpu(cpu) {
+ if (cpu == smp_processor_id())
+ continue;
+
+ wake_up_if_idle(cpu);
+ }
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);