kernel/smp.c - kernel/msm - Gitiles

 /*
  * Generic helpers for smp ipi calls
  *
  * (C) Jens Axboe <jens.axboe@oracle.com> 2008
  */
 #include <linux/rcupdate.h>
 #include <linux/rculist.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/init.h>
 #include <linux/smp.h>
 #include <linux/cpu.h>

 static DEFINE_PER_CPU(struct call_single_queue, call_single_queue);

 static struct {
 	struct list_head	queue;
 	spinlock_t		lock;
 } call_function __cacheline_aligned_in_smp =
 	{
 		.queue		= LIST_HEAD_INIT(call_function.queue),
 		.lock		= __SPIN_LOCK_UNLOCKED(call_function.lock),
 	};

 enum {
 	CSD_FLAG_LOCK		= 0x01,
 };

 struct call_function_data {
 	struct call_single_data	csd;
 	spinlock_t		lock;
 	unsigned int		refs;
 	cpumask_var_t		cpumask;
 };

 struct call_single_queue {
 	struct list_head	list;
 	spinlock_t		lock;
 };

 static DEFINE_PER_CPU(struct call_function_data, cfd_data) = {
 	.lock			= __SPIN_LOCK_UNLOCKED(cfd_data.lock),
 };

 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 (!alloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
 				cpu_to_node(cpu)))
 			return NOTIFY_BAD;
 		break;

 #ifdef CONFIG_CPU_HOTPLUG
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:

 	case CPU_DEAD:
 	case CPU_DEAD_FROZEN:
 		free_cpumask_var(cfd->cpumask);
 		break;
 #endif
 	};

 	return NOTIFY_OK;
 }

 static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
 	.notifier_call		= hotplug_cfd,
 };

 static int __cpuinit init_call_single_data(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
 	int i;

 	for_each_possible_cpu(i) {
 		struct call_single_queue *q = &per_cpu(call_single_queue, i);

 		spin_lock_init(&q->lock);
 		INIT_LIST_HEAD(&q->list);
 	}

 	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
 	register_cpu_notifier(&hotplug_cfd_notifier);

 	return 0;
 }
 early_initcall(init_call_single_data);

 /*
  * 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 *data)
 {
 	while (data->flags & CSD_FLAG_LOCK)
 		cpu_relax();
 }

 static void csd_lock(struct call_single_data *data)
 {
 	csd_lock_wait(data);
 	data->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_mb();
 }

 static void csd_unlock(struct call_single_data *data)
 {
 	WARN_ON(!(data->flags & CSD_FLAG_LOCK));

 	/*
 	 * ensure we're all done before releasing data:
 	 */
 	smp_mb();

 	data->flags &= ~CSD_FLAG_LOCK;
 }

 /*
  * Insert a previously allocated call_single_data element
  * for execution on the given CPU. data must already have
  * ->func, ->info, and ->flags set.
  */
 static
 void generic_exec_single(int cpu, struct call_single_data *data, int wait)
 {
 	struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
 	unsigned long flags;
 	int ipi;

 	spin_lock_irqsave(&dst->lock, flags);
 	ipi = list_empty(&dst->list);
 	list_add_tail(&data->list, &dst->list);
 	spin_unlock_irqrestore(&dst->lock, flags);

 	/*
 	 * 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 (ipi)
 		arch_send_call_function_single_ipi(cpu);

 	if (wait)
 		csd_lock_wait(data);
 }

 /*
  * Invoked by arch to handle an IPI for call function. Must be called with
  * interrupts disabled.
  */
 void generic_smp_call_function_interrupt(void)
 {
 	struct call_function_data *data;
 	int cpu = get_cpu();

 	/*
 	 * Ensure entry is visible on call_function_queue after we have
 	 * entered the IPI. See comment in smp_call_function_many.
 	 * If we don't have this, then we may miss an entry on the list
 	 * and never get another IPI to process it.
 	 */
 	smp_mb();

 	/*
 	 * It's ok to use list_for_each_rcu() here even though we may
 	 * delete 'pos', since list_del_rcu() doesn't clear ->next
 	 */
 	list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
 		int refs;

 		spin_lock(&data->lock);
 		if (!cpumask_test_cpu(cpu, data->cpumask)) {
 			spin_unlock(&data->lock);
 			continue;
 		}
 		cpumask_clear_cpu(cpu, data->cpumask);
 		spin_unlock(&data->lock);

 		data->csd.func(data->csd.info);

 		spin_lock(&data->lock);
 		WARN_ON(data->refs == 0);
 		refs = --data->refs;
 		if (!refs) {
 			spin_lock(&call_function.lock);
 			list_del_rcu(&data->csd.list);
 			spin_unlock(&call_function.lock);
 		}
 		spin_unlock(&data->lock);

 		if (refs)
 			continue;

 		csd_unlock(&data->csd);
 	}

 	put_cpu();
 }

 /*
  * Invoked by arch to handle an IPI for call function single. Must be
  * called from the arch with interrupts disabled.
  */
 void generic_smp_call_function_single_interrupt(void)
 {
 	struct call_single_queue *q = &__get_cpu_var(call_single_queue);
 	unsigned int data_flags;
 	LIST_HEAD(list);

 	spin_lock(&q->lock);
 	list_replace_init(&q->list, &list);
 	spin_unlock(&q->lock);

 	while (!list_empty(&list)) {
 		struct call_single_data *data;

 		data = list_entry(list.next, struct call_single_data, list);
 		list_del(&data->list);

 		/*
 		 * 'data' can be invalid after this call if flags == 0
 		 * (when called through generic_exec_single()),
 		 * so save them away before making the call:
 		 */
 		data_flags = data->flags;

 		data->func(data->info);

 		/*
 		 * Unlocked CSDs are valid through generic_exec_single():
 		 */
 		if (data_flags & CSD_FLAG_LOCK)
 			csd_unlock(data);
 	}
 }

 static DEFINE_PER_CPU(struct call_single_data, csd_data);

 /*
  * 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. Note that @wait
  * will be implicitly turned on in case of allocation failures, since
  * we fall back to on-stack allocation.
  */
 int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 			     int wait)
 {
 	struct call_single_data d = {
 		.flags = 0,
 	};
 	unsigned long flags;
 	int this_cpu;
 	int err = 0;

 	/*
 	 * prevent preemption and reschedule on another processor,
 	 * as well as CPU removal
 	 */
 	this_cpu = get_cpu();

 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);

 	if (cpu == this_cpu) {
 		local_irq_save(flags);
 		func(info);
 		local_irq_restore(flags);
 	} else {
 		if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
 			struct call_single_data *data = &d;

 			if (!wait)
 				data = &__get_cpu_var(csd_data);

 			csd_lock(data);

 			data->func = func;
 			data->info = info;
 			generic_exec_single(cpu, data, wait);
 		} else {
 			err = -ENXIO;	/* CPU not online */
 		}
 	}

 	put_cpu();

 	return err;
 }
 EXPORT_SYMBOL(smp_call_function_single);

 /**
  * __smp_call_function_single(): Run a function on another CPU
  * @cpu: The CPU to run on.
  * @data: Pre-allocated and setup data structure
  *
  * Like smp_call_function_single(), but allow caller to pass in a
  * pre-allocated data structure. Useful for embedding @data inside
  * other structures, for instance.
  */
 void __smp_call_function_single(int cpu, struct call_single_data *data,
 				int wait)
 {
 	csd_lock(data);

 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON_ONCE(wait && irqs_disabled() && !oops_in_progress);

 	generic_exec_single(cpu, data, wait);
 }

 /* Deprecated: shim for archs using old arch_send_call_function_ipi API. */

 #ifndef arch_send_call_function_ipi_mask
 # define arch_send_call_function_ipi_mask(maskp) \
 	 arch_send_call_function_ipi(*(maskp))
 #endif

 /**
  * 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. Note that @wait
  * will be implicitly turned on in case of allocation failures, since
  * we fall back to on-stack allocation.
  *
  * 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,
 			    void (*func)(void *), void *info, bool wait)
 {
 	struct call_function_data *data;
 	unsigned long flags;
 	int cpu, next_cpu, this_cpu = smp_processor_id();

 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);

 	/* 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;
 	}

 	data = &__get_cpu_var(cfd_data);
 	csd_lock(&data->csd);

 	spin_lock_irqsave(&data->lock, flags);
 	data->csd.func = func;
 	data->csd.info = info;
 	cpumask_and(data->cpumask, mask, cpu_online_mask);
 	cpumask_clear_cpu(this_cpu, data->cpumask);
 	data->refs = cpumask_weight(data->cpumask);

 	spin_lock(&call_function.lock);
 	/*
 	 * Place entry at the _HEAD_ of the list, so that any cpu still
 	 * observing the entry in generic_smp_call_function_interrupt()
 	 * will not miss any other list entries:
 	 */
 	list_add_rcu(&data->csd.list, &call_function.queue);
 	spin_unlock(&call_function.lock);

 	spin_unlock_irqrestore(&data->lock, flags);

 	/*
 	 * Make the list addition visible before sending the ipi.
 	 * (IPIs must obey or appear to obey normal Linux cache
 	 * coherency rules -- see comment in generic_exec_single).
 	 */
 	smp_mb();

 	/* Send a message to all CPUs in the map */
 	arch_send_call_function_ipi_mask(data->cpumask);

 	/* Optionally wait for the CPUs to complete */
 	if (wait)
 		csd_lock_wait(&data->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. In case of allocation
  * failure, @wait will be implicitly turned on.
  *
  * 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(void (*func)(void *), 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);

 void ipi_call_lock(void)
 {
 	spin_lock(&call_function.lock);
 }

 void ipi_call_unlock(void)
 {
 	spin_unlock(&call_function.lock);
 }

 void ipi_call_lock_irq(void)
 {
 	spin_lock_irq(&call_function.lock);
 }

 void ipi_call_unlock_irq(void)
 {
 	spin_unlock_irq(&call_function.lock);
 }
	/*
	* Generic helpers for smp ipi calls
	*
	* (C) Jens Axboe <jens.axboe@oracle.com> 2008
	*/
	#include <linux/rcupdate.h>
	#include <linux/rculist.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/percpu.h>
	#include <linux/init.h>
	#include <linux/smp.h>
	#include <linux/cpu.h>

	static DEFINE_PER_CPU(struct call_single_queue, call_single_queue);

	static struct {
	struct list_head queue;
	spinlock_t lock;
	} call_function __cacheline_aligned_in_smp =
	{
	.queue = LIST_HEAD_INIT(call_function.queue),
	.lock = __SPIN_LOCK_UNLOCKED(call_function.lock),
	};

	enum {
	CSD_FLAG_LOCK = 0x01,
	};

	struct call_function_data {
	struct call_single_data csd;
	spinlock_t lock;
	unsigned int refs;
	cpumask_var_t cpumask;
	};

	struct call_single_queue {
	struct list_head list;
	spinlock_t lock;
	};

	static DEFINE_PER_CPU(struct call_function_data, cfd_data) = {
	.lock = __SPIN_LOCK_UNLOCKED(cfd_data.lock),
	};

	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 (!alloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
	cpu_to_node(cpu)))
	return NOTIFY_BAD;
	break;

	#ifdef CONFIG_CPU_HOTPLUG
	case CPU_UP_CANCELED:
	case CPU_UP_CANCELED_FROZEN:

	case CPU_DEAD:
	case CPU_DEAD_FROZEN:
	free_cpumask_var(cfd->cpumask);
	break;
	#endif
	};

	return NOTIFY_OK;
	}

	static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
	.notifier_call = hotplug_cfd,
	};

	static int __cpuinit init_call_single_data(void)
	{
	void cpu = (void )(long)smp_processor_id();
	int i;

	for_each_possible_cpu(i) {
	struct call_single_queue *q = &per_cpu(call_single_queue, i);

	spin_lock_init(&q->lock);
	INIT_LIST_HEAD(&q->list);
	}

	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
	register_cpu_notifier(&hotplug_cfd_notifier);

	return 0;
	}
	early_initcall(init_call_single_data);

	/*
	* 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 *data)
	{
	while (data->flags & CSD_FLAG_LOCK)
	cpu_relax();
	}

	static void csd_lock(struct call_single_data *data)
	{
	csd_lock_wait(data);
	data->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_mb();
	}

	static void csd_unlock(struct call_single_data *data)
	{
	WARN_ON(!(data->flags & CSD_FLAG_LOCK));

	/*
	* ensure we're all done before releasing data:
	*/
	smp_mb();

	data->flags &= ~CSD_FLAG_LOCK;
	}

	/*
	* Insert a previously allocated call_single_data element
	* for execution on the given CPU. data must already have
	* ->func, ->info, and ->flags set.
	*/
	static
	void generic_exec_single(int cpu, struct call_single_data *data, int wait)
	{
	struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
	unsigned long flags;
	int ipi;

	spin_lock_irqsave(&dst->lock, flags);
	ipi = list_empty(&dst->list);
	list_add_tail(&data->list, &dst->list);
	spin_unlock_irqrestore(&dst->lock, flags);

	/*
	* 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 (ipi)
	arch_send_call_function_single_ipi(cpu);

	if (wait)
	csd_lock_wait(data);
	}

	/*
	* Invoked by arch to handle an IPI for call function. Must be called with
	* interrupts disabled.
	*/
	void generic_smp_call_function_interrupt(void)
	{
	struct call_function_data *data;
	int cpu = get_cpu();

	/*
	* Ensure entry is visible on call_function_queue after we have
	* entered the IPI. See comment in smp_call_function_many.
	* If we don't have this, then we may miss an entry on the list
	* and never get another IPI to process it.
	*/
	smp_mb();

	/*
	* It's ok to use list_for_each_rcu() here even though we may
	* delete 'pos', since list_del_rcu() doesn't clear ->next
	*/
	list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
	int refs;

	spin_lock(&data->lock);
	if (!cpumask_test_cpu(cpu, data->cpumask)) {
	spin_unlock(&data->lock);
	continue;
	}
	cpumask_clear_cpu(cpu, data->cpumask);
	spin_unlock(&data->lock);

	data->csd.func(data->csd.info);

	spin_lock(&data->lock);
	WARN_ON(data->refs == 0);
	refs = --data->refs;
	if (!refs) {
	spin_lock(&call_function.lock);
	list_del_rcu(&data->csd.list);
	spin_unlock(&call_function.lock);
	}
	spin_unlock(&data->lock);

	if (refs)
	continue;

	csd_unlock(&data->csd);
	}

	put_cpu();
	}

	/*
	* Invoked by arch to handle an IPI for call function single. Must be
	* called from the arch with interrupts disabled.
	*/
	void generic_smp_call_function_single_interrupt(void)
	{
	struct call_single_queue *q = &__get_cpu_var(call_single_queue);
	unsigned int data_flags;
	LIST_HEAD(list);

	spin_lock(&q->lock);
	list_replace_init(&q->list, &list);
	spin_unlock(&q->lock);

	while (!list_empty(&list)) {
	struct call_single_data *data;

	data = list_entry(list.next, struct call_single_data, list);
	list_del(&data->list);

	/*
	* 'data' can be invalid after this call if flags == 0
	* (when called through generic_exec_single()),
	* so save them away before making the call:
	*/
	data_flags = data->flags;

	data->func(data->info);

	/*
	* Unlocked CSDs are valid through generic_exec_single():
	*/
	if (data_flags & CSD_FLAG_LOCK)
	csd_unlock(data);
	}
	}

	static DEFINE_PER_CPU(struct call_single_data, csd_data);

	/*
	* 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. Note that @wait
	* will be implicitly turned on in case of allocation failures, since
	* we fall back to on-stack allocation.
	*/
	int smp_call_function_single(int cpu, void (func) (void info), void *info,
	int wait)
	{
	struct call_single_data d = {
	.flags = 0,
	};
	unsigned long flags;
	int this_cpu;
	int err = 0;

	/*
	* prevent preemption and reschedule on another processor,
	* as well as CPU removal
	*/
	this_cpu = get_cpu();

	/* Can deadlock when called with interrupts disabled */
	WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);

	if (cpu == this_cpu) {
	local_irq_save(flags);
	func(info);
	local_irq_restore(flags);
	} else {
	if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
	struct call_single_data *data = &d;

	if (!wait)
	data = &__get_cpu_var(csd_data);

	csd_lock(data);

	data->func = func;
	data->info = info;
	generic_exec_single(cpu, data, wait);
	} else {
	err = -ENXIO; /* CPU not online */
	}
	}

	put_cpu();

	return err;
	}
	EXPORT_SYMBOL(smp_call_function_single);

	/**
	* __smp_call_function_single(): Run a function on another CPU
	* @cpu: The CPU to run on.
	* @data: Pre-allocated and setup data structure
	*
	* Like smp_call_function_single(), but allow caller to pass in a
	* pre-allocated data structure. Useful for embedding @data inside
	* other structures, for instance.
	*/
	void __smp_call_function_single(int cpu, struct call_single_data *data,
	int wait)
	{
	csd_lock(data);

	/* Can deadlock when called with interrupts disabled */
	WARN_ON_ONCE(wait && irqs_disabled() && !oops_in_progress);

	generic_exec_single(cpu, data, wait);
	}

	/* Deprecated: shim for archs using old arch_send_call_function_ipi API. */

	#ifndef arch_send_call_function_ipi_mask
	# define arch_send_call_function_ipi_mask(maskp) \
	arch_send_call_function_ipi(*(maskp))
	#endif

	/**
	* 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. Note that @wait
	* will be implicitly turned on in case of allocation failures, since
	* we fall back to on-stack allocation.
	*
	* 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,
	void (func)(void ), void *info, bool wait)
	{
	struct call_function_data *data;
	unsigned long flags;
	int cpu, next_cpu, this_cpu = smp_processor_id();

	/* Can deadlock when called with interrupts disabled */
	WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);

	/* 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;
	}

	data = &__get_cpu_var(cfd_data);
	csd_lock(&data->csd);

	spin_lock_irqsave(&data->lock, flags);
	data->csd.func = func;
	data->csd.info = info;
	cpumask_and(data->cpumask, mask, cpu_online_mask);
	cpumask_clear_cpu(this_cpu, data->cpumask);
	data->refs = cpumask_weight(data->cpumask);

	spin_lock(&call_function.lock);
	/*
	* Place entry at the _HEAD_ of the list, so that any cpu still
	* observing the entry in generic_smp_call_function_interrupt()
	* will not miss any other list entries:
	*/
	list_add_rcu(&data->csd.list, &call_function.queue);
	spin_unlock(&call_function.lock);

	spin_unlock_irqrestore(&data->lock, flags);

	/*
	* Make the list addition visible before sending the ipi.
	* (IPIs must obey or appear to obey normal Linux cache
	* coherency rules -- see comment in generic_exec_single).
	*/
	smp_mb();

	/* Send a message to all CPUs in the map */
	arch_send_call_function_ipi_mask(data->cpumask);

	/* Optionally wait for the CPUs to complete */
	if (wait)
	csd_lock_wait(&data->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. In case of allocation
	* failure, @wait will be implicitly turned on.
	*
	* 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(void (func)(void ), 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);

	void ipi_call_lock(void)
	{
	spin_lock(&call_function.lock);
	}

	void ipi_call_unlock(void)
	{
	spin_unlock(&call_function.lock);
	}

	void ipi_call_lock_irq(void)
	{
	spin_lock_irq(&call_function.lock);
	}

	void ipi_call_unlock_irq(void)
	{
	spin_unlock_irq(&call_function.lock);
	}