/* * 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" enum {	CSD_FLAG_LOCK		= 0x01,	CSD_FLAG_WAIT		= 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 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);		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_percpu(cfd->csd);		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 (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_WAIT) && !(csd->flags & CSD_FLAG_LOCK)); 	/*	 * ensure we're all done before releasing data:	 */	smp_mb(); 	csd->flags &= ~CSD_FLAG_LOCK;} 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, int wait){	struct call_single_data csd_stack = { .flags = 0 };	unsigned long flags;  	if (cpu == smp_processor_id()) {		local_irq_save(flags);		func(info);		local_irq_restore(flags);		return 0;	}  	if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu))		return -ENXIO;  	if (!csd) {		csd = &csd_stack;		if (!wait)			csd = &__get_cpu_var(csd_data);	} 	csd_lock(csd); 	csd->func = func;	csd->info = info; 	if (wait)		csd->flags |= CSD_FLAG_WAIT; 	/*	 * 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); 	if (wait)		csd_lock_wait(csd); 	return 0;} /* * 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 llist_node *entry;	struct call_single_data *csd, *csd_next; 	/*	 * Shouldn't receive this interrupt on a cpu that is not yet online.	 */	WARN_ON_ONCE(!cpu_online(smp_processor_id())); 	entry = llist_del_all(&__get_cpu_var(call_single_queue));	entry = llist_reverse_order(entry); 	llist_for_each_entry_safe(csd, csd_next, entry, llist) {		csd->func(csd->info);		csd_unlock(csd);	}} /* * 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){	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); 	err = generic_exec_single(cpu, NULL, func, info, wait); 	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();	err = generic_exec_single(cpu, csd, csd->func, csd->info, 0);	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 = &__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; 	for_each_cpu(cpu, cfd->cpumask) {		struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu); 		csd_lock(csd);		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 */

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