/* * 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/export.h>#include <linux/percpu.h>#include <linux/init.h>#include <linux/gfp.h>#include <linux/smp.h>#include <linux/cpu.h> #include "smpboot.h" #ifdef CONFIG_USE_GENERIC_SMP_HELPERSenum {	CSD_FLAG_LOCK		= 0x01,}; struct call_function_data {	struct call_single_data	__percpu *csd;	cpumask_var_t		cpumask;	cpumask_var_t		cpumask_ipi;}; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); struct call_single_queue {	struct list_head	list;	raw_spinlock_t		lock;}; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); 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 notifier_from_errno(-ENOMEM);		if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, 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: 	case CPU_DEAD:	case CPU_DEAD_FROZEN:		free_cpumask_var(cfd->cpumask);		free_cpumask_var(cfd->cpumask_ipi);		free_percpu(cfd->csd);		break;#endif	}; 	return NOTIFY_OK;} static struct notifier_block __cpuinitdata 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) {		struct call_single_queue *q = &per_cpu(call_single_queue, i); 		raw_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);} /* * 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 (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_mb();} 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_mb(); 	csd->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 *csd, int wait){	struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);	unsigned long flags;	int ipi; 	raw_spin_lock_irqsave(&dst->lock, flags);	ipi = list_empty(&dst->list);	list_add_tail(&csd->list, &dst->list);	raw_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(csd);} /* * 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);	LIST_HEAD(list); 	/*	 * Shouldn't receive this interrupt on a cpu that is not yet online.	 */	WARN_ON_ONCE(!cpu_online(smp_processor_id())); 	raw_spin_lock(&q->lock);	list_replace_init(&q->list, &list);	raw_spin_unlock(&q->lock); 	while (!list_empty(&list)) {		struct call_single_data *csd;		unsigned int csd_flags; 		csd = list_entry(list.next, struct call_single_data, list);		list_del(&csd->list); 		/*		 * 'csd' can be invalid after this call if flags == 0		 * (when called through generic_exec_single()),		 * so save them away before making the call:		 */		csd_flags = csd->flags; 		csd->func(csd->info); 		/*		 * Unlocked CSDs are valid through generic_exec_single():		 */		if (csd_flags & CSD_FLAG_LOCK)			csd_unlock(csd);	}} static DEFINE_PER_CPU_SHARED_ALIGNED(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. */int smp_call_function_single(int cpu, smp_call_func_t func, 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 *csd = &d; 			if (!wait)				csd = &__get_cpu_var(csd_data); 			csd_lock(csd); 			csd->func = func;			csd->info = info;			generic_exec_single(cpu, csd, wait);		} else {			err = -ENXIO;	/* CPU not online */		}	} 	put_cpu(); 	return err;}EXPORT_SYMBOL(smp_call_function_single); /* * 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). * Note that @wait will be implicitly turned on in case of allocation failures, * since we fall back to on-stack allocation. * * 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_single(): Run a function on a specific CPU * @cpu: The CPU to run on. * @data: Pre-allocated and setup data structure * @wait: If true, wait until function has completed on specified CPU. * * 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 *csd,				int wait){	unsigned int this_cpu;	unsigned long flags; 	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(smp_processor_id()) && wait && irqs_disabled()		     && !oops_in_progress); 	if (cpu == this_cpu) {		local_irq_save(flags);		csd->func(csd->info);		local_irq_restore(flags);	} else {		csd_lock(csd);		generic_exec_single(cpu, csd, wait);	}	put_cpu();} /** * 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 = &__get_cpu_var(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; 	/*	 * After we put an entry into the list, cfd->cpumask may be cleared	 * again when another CPU sends another IPI for a SMP function call, so	 * cfd->cpumask will be zero.	 */	cpumask_copy(cfd->cpumask_ipi, cfd->cpumask); 	for_each_cpu(cpu, cfd->cpumask) {		struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);		struct call_single_queue *dst =					&per_cpu(call_single_queue, cpu);		unsigned long flags; 		csd_lock(csd);		csd->func = func;		csd->info = info; 		raw_spin_lock_irqsave(&dst->lock, flags);		list_add_tail(&csd->list, &dst->list);		raw_spin_unlock_irqrestore(&dst->lock, flags);	} 	/* 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) {			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);#endif /* USE_GENERIC_SMP_HELPERS */ /* 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;} 

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