/* * Fast batching percpu counters. */ #include <linux/percpu_counter.h>#include <linux/notifier.h>#include <linux/mutex.h>#include <linux/init.h>#include <linux/cpu.h>#include <linux/module.h>#include <linux/debugobjects.h> #ifdef CONFIG_HOTPLUG_CPUstatic LIST_HEAD(percpu_counters);static DEFINE_SPINLOCK(percpu_counters_lock);#endif #ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER static struct debug_obj_descr percpu_counter_debug_descr; static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state){	struct percpu_counter *fbc = addr; 	switch (state) {	case ODEBUG_STATE_ACTIVE:		percpu_counter_destroy(fbc);		debug_object_free(fbc, &percpu_counter_debug_descr);		return 1;	default:		return 0;	}} static struct debug_obj_descr percpu_counter_debug_descr = {	.name		= "percpu_counter",	.fixup_free	= percpu_counter_fixup_free,}; static inline void debug_percpu_counter_activate(struct percpu_counter *fbc){	debug_object_init(fbc, &percpu_counter_debug_descr);	debug_object_activate(fbc, &percpu_counter_debug_descr);} static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc){	debug_object_deactivate(fbc, &percpu_counter_debug_descr);	debug_object_free(fbc, &percpu_counter_debug_descr);} #else	/* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */static inline void debug_percpu_counter_activate(struct percpu_counter *fbc){ }static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc){ }#endif	/* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */ void percpu_counter_set(struct percpu_counter *fbc, s64 amount){	int cpu;	unsigned long flags; 	raw_spin_lock_irqsave(&fbc->lock, flags);	for_each_possible_cpu(cpu) {		s32 *pcount = per_cpu_ptr(fbc->counters, cpu);		*pcount = 0;	}	fbc->count = amount;	raw_spin_unlock_irqrestore(&fbc->lock, flags);}EXPORT_SYMBOL(percpu_counter_set); void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch){	s64 count; 	preempt_disable();	count = __this_cpu_read(*fbc->counters) + amount;	if (count >= batch || count <= -batch) {		unsigned long flags;		raw_spin_lock_irqsave(&fbc->lock, flags);		fbc->count += count;		__this_cpu_sub(*fbc->counters, count - amount);		raw_spin_unlock_irqrestore(&fbc->lock, flags);	} else {		this_cpu_add(*fbc->counters, amount);	}	preempt_enable();}EXPORT_SYMBOL(__percpu_counter_add); /* * Add up all the per-cpu counts, return the result.  This is a more accurate * but much slower version of percpu_counter_read_positive() */s64 __percpu_counter_sum(struct percpu_counter *fbc){	s64 ret;	int cpu;	unsigned long flags; 	raw_spin_lock_irqsave(&fbc->lock, flags);	ret = fbc->count;	for_each_online_cpu(cpu) {		s32 *pcount = per_cpu_ptr(fbc->counters, cpu);		ret += *pcount;	}	raw_spin_unlock_irqrestore(&fbc->lock, flags);	return ret;}EXPORT_SYMBOL(__percpu_counter_sum); int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,			  struct lock_class_key *key){	raw_spin_lock_init(&fbc->lock);	lockdep_set_class(&fbc->lock, key);	fbc->count = amount;	fbc->counters = alloc_percpu(s32);	if (!fbc->counters)		return -ENOMEM; 	debug_percpu_counter_activate(fbc); #ifdef CONFIG_HOTPLUG_CPU	INIT_LIST_HEAD(&fbc->list);	spin_lock(&percpu_counters_lock);	list_add(&fbc->list, &percpu_counters);	spin_unlock(&percpu_counters_lock);#endif	return 0;}EXPORT_SYMBOL(__percpu_counter_init); void percpu_counter_destroy(struct percpu_counter *fbc){	if (!fbc->counters)		return; 	debug_percpu_counter_deactivate(fbc); #ifdef CONFIG_HOTPLUG_CPU	spin_lock(&percpu_counters_lock);	list_del(&fbc->list);	spin_unlock(&percpu_counters_lock);#endif	free_percpu(fbc->counters);	fbc->counters = NULL;}EXPORT_SYMBOL(percpu_counter_destroy); int percpu_counter_batch __read_mostly = 32;EXPORT_SYMBOL(percpu_counter_batch); static void compute_batch_value(void){	int nr = num_online_cpus(); 	percpu_counter_batch = max(32, nr*2);} static int percpu_counter_hotcpu_callback(struct notifier_block *nb,					unsigned long action, void *hcpu){#ifdef CONFIG_HOTPLUG_CPU	unsigned int cpu;	struct percpu_counter *fbc; 	compute_batch_value();	if (action != CPU_DEAD)		return NOTIFY_OK; 	cpu = (unsigned long)hcpu;	spin_lock(&percpu_counters_lock);	list_for_each_entry(fbc, &percpu_counters, list) {		s32 *pcount;		unsigned long flags; 		raw_spin_lock_irqsave(&fbc->lock, flags);		pcount = per_cpu_ptr(fbc->counters, cpu);		fbc->count += *pcount;		*pcount = 0;		raw_spin_unlock_irqrestore(&fbc->lock, flags);	}	spin_unlock(&percpu_counters_lock);#endif	return NOTIFY_OK;} /* * Compare counter against given value. * Return 1 if greater, 0 if equal and -1 if less */int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs){	s64	count; 	count = percpu_counter_read(fbc);	/* Check to see if rough count will be sufficient for comparison */	if (abs(count - rhs) > (percpu_counter_batch*num_online_cpus())) {		if (count > rhs)			return 1;		else			return -1;	}	/* Need to use precise count */	count = percpu_counter_sum(fbc);	if (count > rhs)		return 1;	else if (count < rhs)		return -1;	else		return 0;}EXPORT_SYMBOL(percpu_counter_compare); static int __init percpu_counter_startup(void){	compute_batch_value();	hotcpu_notifier(percpu_counter_hotcpu_callback, 0);	return 0;}module_init(percpu_counter_startup);