/* * 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;	atomic_t		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); static inthotplug_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 NOTIFY_BAD;		break; #ifdef CONFIG_HOTPLUG_CPU	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. */staticvoid 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(); 	/*	 * Shouldn't receive this interrupt on a cpu that is not yet online.	 */	WARN_ON_ONCE(!cpu_online(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; 		if (!cpumask_test_and_clear_cpu(cpu, data->cpumask))			continue; 		data->csd.func(data->csd.info); 		refs = atomic_dec_return(&data->refs);		WARN_ON(refs < 0);		if (!refs) {			spin_lock(&call_function.lock);			list_del_rcu(&data->csd.list);			spin_unlock(&call_function.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); 	/*	 * Shouldn't receive this interrupt on a cpu that is not yet online.	 */	WARN_ON_ONCE(!cpu_online(smp_processor_id())); 	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.	 * 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); 	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.	 * 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(smp_processor_id()) && wait && irqs_disabled()		     && !oops_in_progress); 	generic_exec_single(cpu, data, wait);} /** * 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.	 * 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); 	/* 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); 	data->csd.func = func;	data->csd.info = info;	cpumask_and(data->cpumask, mask, cpu_online_mask);	cpumask_clear_cpu(this_cpu, data->cpumask);	atomic_set(&data->refs, cpumask_weight(data->cpumask)); 	spin_lock_irqsave(&call_function.lock, flags);	/*	 * 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_irqrestore(&call_function.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);}