Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1015 insertions, 0 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
new file mode 100644
index 000000000..b0684b4c1
--- /dev/null
+++ b/kernel/smp.c
@@ -0,0 +1,1015 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic helpers for smp ipi calls
+ *
+ * (C) Jens Axboe <jens.axboe@oracle.com> 2008
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#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/interrupt.h>
+#include <linux/gfp.h>
+#include <linux/smp.h>
+#include <linux/cpu.h>
+#include <linux/sched.h>
+#include <linux/sched/idle.h>
+#include <linux/hypervisor.h>
+#include <linux/sched/clock.h>
+#include <linux/nmi.h>
+#include <linux/sched/debug.h>
+
+#include "smpboot.h"
+#include "sched/smp.h"
+
+#define CSD_TYPE(_csd)	((_csd)->flags & CSD_FLAG_TYPE_MASK)
+
+struct call_function_data {
+	call_single_data_t	__percpu *csd;
+	cpumask_var_t		cpumask;
+	cpumask_var_t		cpumask_ipi;
+};
+
+static DEFINE_PER_CPU_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);
+
+int smpcfd_prepare_cpu(unsigned int cpu)
+{
+	struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
+
+	if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
+				     cpu_to_node(cpu)))
+		return -ENOMEM;
+	if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
+				     cpu_to_node(cpu))) {
+		free_cpumask_var(cfd->cpumask);
+		return -ENOMEM;
+	}
+	cfd->csd = alloc_percpu(call_single_data_t);
+	if (!cfd->csd) {
+		free_cpumask_var(cfd->cpumask);
+		free_cpumask_var(cfd->cpumask_ipi);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+int smpcfd_dead_cpu(unsigned int cpu)
+{
+	struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
+
+	free_cpumask_var(cfd->cpumask);
+	free_cpumask_var(cfd->cpumask_ipi);
+	free_percpu(cfd->csd);
+	return 0;
+}
+
+int smpcfd_dying_cpu(unsigned int cpu)
+{
+	/*
+	 * 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);
+	irq_work_run();
+	return 0;
+}
+
+void __init call_function_init(void)
+{
+	int i;
+
+	for_each_possible_cpu(i)
+		init_llist_head(&per_cpu(call_single_queue, i));
+
+	smpcfd_prepare_cpu(smp_processor_id());
+}
+
+#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
+
+static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
+static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
+static DEFINE_PER_CPU(void *, cur_csd_info);
+
+#define CSD_LOCK_TIMEOUT (5ULL * NSEC_PER_SEC)
+static atomic_t csd_bug_count = ATOMIC_INIT(0);
+
+/* Record current CSD work for current CPU, NULL to erase. */
+static void csd_lock_record(struct __call_single_data *csd)
+{
+	if (!csd) {
+		smp_mb(); /* NULL cur_csd after unlock. */
+		__this_cpu_write(cur_csd, NULL);
+		return;
+	}
+	__this_cpu_write(cur_csd_func, csd->func);
+	__this_cpu_write(cur_csd_info, csd->info);
+	smp_wmb(); /* func and info before csd. */
+	__this_cpu_write(cur_csd, csd);
+	smp_mb(); /* Update cur_csd before function call. */
+		  /* Or before unlock, as the case may be. */
+}
+
+static __always_inline int csd_lock_wait_getcpu(struct __call_single_data *csd)
+{
+	unsigned int csd_type;
+
+	csd_type = CSD_TYPE(csd);
+	if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC)
+		return csd->dst; /* Other CSD_TYPE_ values might not have ->dst. */
+	return -1;
+}
+
+/*
+ * Complain if too much time spent waiting.  Note that only
+ * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU,
+ * so waiting on other types gets much less information.
+ */
+static __always_inline bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *ts1, int *bug_id)
+{
+	int cpu = -1;
+	int cpux;
+	bool firsttime;
+	u64 ts2, ts_delta;
+	call_single_data_t *cpu_cur_csd;
+	unsigned int flags = READ_ONCE(csd->flags);
+
+	if (!(flags & CSD_FLAG_LOCK)) {
+		if (!unlikely(*bug_id))
+			return true;
+		cpu = csd_lock_wait_getcpu(csd);
+		pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n",
+			 *bug_id, raw_smp_processor_id(), cpu);
+		return true;
+	}
+
+	ts2 = sched_clock();
+	ts_delta = ts2 - *ts1;
+	if (likely(ts_delta <= CSD_LOCK_TIMEOUT))
+		return false;
+
+	firsttime = !*bug_id;
+	if (firsttime)
+		*bug_id = atomic_inc_return(&csd_bug_count);
+	cpu = csd_lock_wait_getcpu(csd);
+	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
+		cpux = 0;
+	else
+		cpux = cpu;
+	cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */
+	pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n",
+		 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0,
+		 cpu, csd->func, csd->info);
+	if (cpu_cur_csd && csd != cpu_cur_csd) {
+		pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",
+			 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),
+			 READ_ONCE(per_cpu(cur_csd_info, cpux)));
+	} else {
+		pr_alert("\tcsd: CSD lock (#%d) %s.\n",
+			 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");
+	}
+	if (cpu >= 0) {
+		if (!trigger_single_cpu_backtrace(cpu))
+			dump_cpu_task(cpu);
+		if (!cpu_cur_csd) {
+			pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
+			arch_send_call_function_single_ipi(cpu);
+		}
+	}
+	dump_stack();
+	*ts1 = ts2;
+
+	return false;
+}
+
+/*
+ * 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 __always_inline void csd_lock_wait(struct __call_single_data *csd)
+{
+	int bug_id = 0;
+	u64 ts0, ts1;
+
+	ts1 = ts0 = sched_clock();
+	for (;;) {
+		if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id))
+			break;
+		cpu_relax();
+	}
+	smp_acquire__after_ctrl_dep();
+}
+
+#else
+static void csd_lock_record(struct __call_single_data *csd)
+{
+}
+
+static __always_inline void csd_lock_wait(struct __call_single_data *csd)
+{
+	smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
+}
+#endif
+
+static __always_inline 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_t structure:
+	 */
+	smp_wmb();
+}
+
+static __always_inline 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(call_single_data_t, csd_data);
+
+void __smp_call_single_queue(int cpu, struct llist_node *node)
+{
+	/*
+	 * 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(node, &per_cpu(call_single_queue, cpu)))
+		send_call_function_single_ipi(cpu);
+}
+
+/*
+ * Insert a previously allocated call_single_data_t 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)
+{
+	if (cpu == smp_processor_id()) {
+		smp_call_func_t func = csd->func;
+		void *info = csd->info;
+		unsigned long flags;
+
+		/*
+		 * We can unlock early even for the synchronous on-stack case,
+		 * since we're doing this from the same CPU..
+		 */
+		csd_lock_record(csd);
+		csd_unlock(csd);
+		local_irq_save(flags);
+		func(info);
+		csd_lock_record(NULL);
+		local_irq_restore(flags);
+		return 0;
+	}
+
+	if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
+		csd_unlock(csd);
+		return -ENXIO;
+	}
+
+	__smp_call_single_queue(cpu, &csd->llist);
+
+	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)
+{
+	call_single_data_t *csd, *csd_next;
+	struct llist_node *entry, *prev;
+	struct llist_head *head;
+	static bool warned;
+
+	lockdep_assert_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 && entry != NULL)) {
+		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) {
+			switch (CSD_TYPE(csd)) {
+			case CSD_TYPE_ASYNC:
+			case CSD_TYPE_SYNC:
+			case CSD_TYPE_IRQ_WORK:
+				pr_warn("IPI callback %pS sent to offline CPU\n",
+					csd->func);
+				break;
+
+			case CSD_TYPE_TTWU:
+				pr_warn("IPI task-wakeup sent to offline CPU\n");
+				break;
+
+			default:
+				pr_warn("IPI callback, unknown type %d, sent to offline CPU\n",
+					CSD_TYPE(csd));
+				break;
+			}
+		}
+	}
+
+	/*
+	 * First; run all SYNC callbacks, people are waiting for us.
+	 */
+	prev = NULL;
+	llist_for_each_entry_safe(csd, csd_next, entry, llist) {
+		/* Do we wait until *after* callback? */
+		if (CSD_TYPE(csd) == CSD_TYPE_SYNC) {
+			smp_call_func_t func = csd->func;
+			void *info = csd->info;
+
+			if (prev) {
+				prev->next = &csd_next->llist;
+			} else {
+				entry = &csd_next->llist;
+			}
+
+			csd_lock_record(csd);
+			func(info);
+			csd_unlock(csd);
+			csd_lock_record(NULL);
+		} else {
+			prev = &csd->llist;
+		}
+	}
+
+	if (!entry)
+		return;
+
+	/*
+	 * Second; run all !SYNC callbacks.
+	 */
+	prev = NULL;
+	llist_for_each_entry_safe(csd, csd_next, entry, llist) {
+		int type = CSD_TYPE(csd);
+
+		if (type != CSD_TYPE_TTWU) {
+			if (prev) {
+				prev->next = &csd_next->llist;
+			} else {
+				entry = &csd_next->llist;
+			}
+
+			if (type == CSD_TYPE_ASYNC) {
+				smp_call_func_t func = csd->func;
+				void *info = csd->info;
+
+				csd_lock_record(csd);
+				csd_unlock(csd);
+				func(info);
+				csd_lock_record(NULL);
+			} else if (type == CSD_TYPE_IRQ_WORK) {
+				irq_work_single(csd);
+			}
+
+		} else {
+			prev = &csd->llist;
+		}
+	}
+
+	/*
+	 * Third; only CSD_TYPE_TTWU is left, issue those.
+	 */
+	if (entry)
+		sched_ttwu_pending(entry);
+}
+
+void flush_smp_call_function_from_idle(void)
+{
+	unsigned long flags;
+
+	if (llist_empty(this_cpu_ptr(&call_single_queue)))
+		return;
+
+	local_irq_save(flags);
+	flush_smp_call_function_queue(true);
+	if (local_softirq_pending())
+		do_softirq();
+
+	local_irq_restore(flags);
+}
+
+/*
+ * 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)
+{
+	call_single_data_t *csd;
+	call_single_data_t csd_stack = {
+		.flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC,
+	};
+	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);
+
+	/*
+	 * When @wait we can deadlock when we interrupt between llist_add() and
+	 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
+	 * csd_lock() on because the interrupt context uses the same csd
+	 * storage.
+	 */
+	WARN_ON_ONCE(!in_task());
+
+	csd = &csd_stack;
+	if (!wait) {
+		csd = this_cpu_ptr(&csd_data);
+		csd_lock(csd);
+	}
+
+	csd->func = func;
+	csd->info = info;
+#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
+	csd->src = smp_processor_id();
+	csd->dst = cpu;
+#endif
+
+	err = generic_exec_single(cpu, csd);
+
+	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.
+ *
+ * If the function is called with one csd which has not yet been
+ * processed by previous call to smp_call_function_single_async(), the
+ * function will return immediately with -EBUSY showing that the csd
+ * object is still in progress.
+ *
+ * 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();
+
+	if (csd->flags & CSD_FLAG_LOCK) {
+		err = -EBUSY;
+		goto out;
+	}
+
+	csd->flags = CSD_FLAG_LOCK;
+	smp_wmb();
+
+	err = generic_exec_single(cpu, csd);
+
+out:
+	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);
+
+static void smp_call_function_many_cond(const struct cpumask *mask,
+					smp_call_func_t func, void *info,
+					bool wait, smp_cond_func_t cond_func)
+{
+	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);
+
+	/*
+	 * When @wait we can deadlock when we interrupt between llist_add() and
+	 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
+	 * csd_lock() on because the interrupt context uses the same csd
+	 * storage.
+	 */
+	WARN_ON_ONCE(!in_task());
+
+	/* 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) {
+		if (!cond_func || cond_func(cpu, info))
+			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;
+
+	cpumask_clear(cfd->cpumask_ipi);
+	for_each_cpu(cpu, cfd->cpumask) {
+		call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
+
+		if (cond_func && !cond_func(cpu, info))
+			continue;
+
+		csd_lock(csd);
+		if (wait)
+			csd->flags |= CSD_TYPE_SYNC;
+		csd->func = func;
+		csd->info = info;
+#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
+		csd->src = smp_processor_id();
+		csd->dst = cpu;
+#endif
+		if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
+			__cpumask_set_cpu(cpu, cfd->cpumask_ipi);
+	}
+
+	/* Send a message to all CPUs in the map */
+	arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
+
+	if (wait) {
+		for_each_cpu(cpu, cfd->cpumask) {
+			call_single_data_t *csd;
+
+			csd = per_cpu_ptr(cfd->csd, cpu);
+			csd_lock_wait(csd);
+		}
+	}
+}
+
+/**
+ * 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)
+{
+	smp_call_function_many_cond(mask, func, info, wait, NULL);
+}
+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.
+ */
+void 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();
+}
+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;
+
+	if (get_option(&str, &nr_cpus) && 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 */
+unsigned 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;
+}
+
+/* Called by boot processor to activate the rest. */
+void __init smp_init(void)
+{
+	int num_nodes, num_cpus;
+
+	idle_threads_init();
+	cpuhp_threads_init();
+
+	pr_info("Bringing up secondary CPUs ...\n");
+
+	bringup_nonboot_cpus(setup_max_cpus);
+
+	num_nodes = num_online_nodes();
+	num_cpus  = num_online_cpus();
+	pr_info("Brought up %d node%s, %d CPU%s\n",
+		num_nodes, (num_nodes > 1 ? "s" : ""),
+		num_cpus,  (num_cpus  > 1 ? "s" : ""));
+
+	/* Any cleanup work */
+	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().
+ */
+void on_each_cpu(smp_call_func_t func, void *info, int wait)
+{
+	unsigned long flags;
+
+	preempt_disable();
+	smp_call_function(func, info, wait);
+	local_irq_save(flags);
+	func(info);
+	local_irq_restore(flags);
+	preempt_enable();
+}
+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 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.
+ *
+ * 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_mask(smp_cond_func_t cond_func, smp_call_func_t func,
+			   void *info, bool wait, const struct cpumask *mask)
+{
+	int cpu = get_cpu();
+
+	smp_call_function_many_cond(mask, func, info, wait, cond_func);
+	if (cpumask_test_cpu(cpu, mask) && cond_func(cpu, info)) {
+		unsigned long flags;
+
+		local_irq_save(flags);
+		func(info);
+		local_irq_restore(flags);
+	}
+	put_cpu();
+}
+EXPORT_SYMBOL(on_each_cpu_cond_mask);
+
+void on_each_cpu_cond(smp_cond_func_t cond_func, smp_call_func_t func,
+		      void *info, bool wait)
+{
+	on_each_cpu_cond_mask(cond_func, func, info, wait, cpu_online_mask);
+}
+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);
+
+/**
+ * smp_call_on_cpu - Call a function on a specific cpu
+ *
+ * Used to call a function on a specific cpu and wait for it to return.
+ * Optionally make sure the call is done on a specified physical cpu via vcpu
+ * pinning in order to support virtualized environments.
+ */
+struct smp_call_on_cpu_struct {
+	struct work_struct	work;
+	struct completion	done;
+	int			(*func)(void *);
+	void			*data;
+	int			ret;
+	int			cpu;
+};
+
+static void smp_call_on_cpu_callback(struct work_struct *work)
+{
+	struct smp_call_on_cpu_struct *sscs;
+
+	sscs = container_of(work, struct smp_call_on_cpu_struct, work);
+	if (sscs->cpu >= 0)
+		hypervisor_pin_vcpu(sscs->cpu);
+	sscs->ret = sscs->func(sscs->data);
+	if (sscs->cpu >= 0)
+		hypervisor_pin_vcpu(-1);
+
+	complete(&sscs->done);
+}
+
+int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
+{
+	struct smp_call_on_cpu_struct sscs = {
+		.done = COMPLETION_INITIALIZER_ONSTACK(sscs.done),
+		.func = func,
+		.data = par,
+		.cpu  = phys ? cpu : -1,
+	};
+
+	INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
+
+	if (cpu >= nr_cpu_ids || !cpu_online(cpu))
+		return -ENXIO;
+
+	queue_work_on(cpu, system_wq, &sscs.work);
+	wait_for_completion(&sscs.done);
+
+	return sscs.ret;
+}
+EXPORT_SYMBOL_GPL(smp_call_on_cpu);